1
|
Neyens DM, Brenner L, Calkins R, Winzenried ET, Ritter RC, Appleyard SM. CCK-sensitive C fibers activate NTS leptin receptor-expressing neurons via NMDA receptors. Am J Physiol Regul Integr Comp Physiol 2024; 326:R383-R400. [PMID: 38105761 DOI: 10.1152/ajpregu.00238.2022] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2022] [Revised: 12/07/2023] [Accepted: 12/07/2023] [Indexed: 12/19/2023]
Abstract
The hormone leptin reduces food intake through actions in the peripheral and central nervous systems, including in the hindbrain nucleus of the solitary tract (NTS). The NTS receives viscerosensory information via vagal afferents, including information from the gastrointestinal tract, which is then relayed to other central nervous system (CNS) sites critical for control of food intake. Leptin receptors (lepRs) are expressed by a subpopulation of NTS neurons, and knockdown of these receptors increases both food intake and body weight. Recently, we demonstrated that leptin increases vagal activation of lepR-expressing neurons via increased NMDA receptor (NMDAR) currents, thereby potentiating vagally evoked firing. Furthermore, chemogenetic activation of these neurons was recently shown to inhibit food intake. However, the vagal inputs these neurons receive had not been characterized. Here we performed whole cell recordings in brain slices taken from lepRCre × floxedTdTomato mice and found that lepR neurons of the NTS are directly activated by monosynaptic inputs from C-type afferents sensitive to the transient receptor potential vanilloid type 1 (TRPV1) agonist capsaicin. CCK administered onto NTS slices stimulated spontaneous glutamate release onto lepR neurons and induced action potential firing, an effect mediated by CCKR1. Interestingly, NMDAR activation contributed to the current carried by spontaneous excitatory postsynaptic currents (EPSCs) and enhanced CCK-induced firing. Peripheral CCK also increased c-fos expression in these neurons, suggesting they are activated by CCK-sensitive vagal afferents in vivo. Our results indicate that the majority of NTS lepR neurons receive direct inputs from CCK-sensitive C vagal-type afferents, with both peripheral and central CCK capable of activating these neurons and NMDARs able to potentiate these effects.
Collapse
Affiliation(s)
- Drew M Neyens
- Department of Integrated Physiology and Neuroscience, Washington State University, Pullman, Washington, United States
| | - Lynne Brenner
- Department of Integrated Physiology and Neuroscience, Washington State University, Pullman, Washington, United States
| | - Rowan Calkins
- Department of Integrated Physiology and Neuroscience, Washington State University, Pullman, Washington, United States
| | - Eric T Winzenried
- Department of Integrated Physiology and Neuroscience, Washington State University, Pullman, Washington, United States
| | - Robert C Ritter
- Department of Integrated Physiology and Neuroscience, Washington State University, Pullman, Washington, United States
| | - Suzanne M Appleyard
- Department of Integrated Physiology and Neuroscience, Washington State University, Pullman, Washington, United States
| |
Collapse
|
2
|
Zsombok A, Desmoulins LD, Derbenev AV. Sympathetic circuits regulating hepatic glucose metabolism: where we stand. Physiol Rev 2024; 104:85-101. [PMID: 37440208 PMCID: PMC11281813 DOI: 10.1152/physrev.00005.2023] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2023] [Revised: 06/12/2023] [Accepted: 07/10/2023] [Indexed: 07/14/2023] Open
Abstract
The prevalence of metabolic disorders, including type 2 diabetes mellitus, continues to increase worldwide. Although newer and more advanced therapies are available, current treatments are still inadequate and the search for solutions remains. The regulation of energy homeostasis, including glucose metabolism, involves an exchange of information between the nervous systems and peripheral organs and tissues; therefore, developing treatments to alter central and/or peripheral neural pathways could be an alternative solution to modulate whole body metabolism. Liver glucose production and storage are major mechanisms controlling glycemia, and the autonomic nervous system plays an important role in the regulation of hepatic functions. Autonomic nervous system imbalance contributes to excessive hepatic glucose production and thus to the development and progression of type 2 diabetes mellitus. At cellular levels, change in neuronal activity is one of the underlying mechanisms of autonomic imbalance; therefore, modulation of the excitability of neurons involved in autonomic outflow governance has the potential to improve glycemic status. Tissue-specific subsets of preautonomic neurons differentially control autonomic outflow; therefore, detailed information about neural circuits and properties of liver-related neurons is necessary for the development of strategies to regulate liver functions via the autonomic nerves. This review provides an overview of our current understanding of the hypothalamus-ventral brainstem-liver pathway involved in the sympathetic regulation of the liver, outlines strategies to identify organ-related neurons, and summarizes neuronal plasticity during diabetic conditions with a particular focus on liver-related neurons in the paraventricular nucleus.
Collapse
Affiliation(s)
- Andrea Zsombok
- Department of Physiology, School of Medicine, Tulane University, New Orleans, Louisiana, United States
- Tulane Brain Institute, Tulane University, New Orleans, Louisiana, United States
| | - Lucie D Desmoulins
- Department of Physiology, School of Medicine, Tulane University, New Orleans, Louisiana, United States
| | - Andrei V Derbenev
- Department of Physiology, School of Medicine, Tulane University, New Orleans, Louisiana, United States
- Tulane Brain Institute, Tulane University, New Orleans, Louisiana, United States
| |
Collapse
|
3
|
Sun HZ, Li CY, Shi Y, Li JJ, Wang YY, Han LN, Zhu LJ, Zhang YF. Effect of exogenous hydrogen sulfide in the nucleus tractus solitarius on gastric motility in rats. World J Gastroenterol 2023; 29:4557-4570. [PMID: 37621756 PMCID: PMC10445002 DOI: 10.3748/wjg.v29.i29.4557] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/18/2023] [Revised: 06/29/2023] [Accepted: 07/19/2023] [Indexed: 08/02/2023] Open
Abstract
BACKGROUND Hydrogen sulfide (H2S) is a recently discovered gaseous neurotransmitter in the nervous and gastrointestinal systems. It exerts its effects through multiple signaling pathways, impacting various physiological activities. The nucleus tractus solitarius (NTS), a vital nucleus involved in visceral sensation, was investigated in this study to understand the role of H2S in regulating gastric function in rats. AIM To examine whether H2S affects the nuclear factor kappa-B (NF-κB) and transient receptor potential vanilloid 1 pathways and the neurokinin 1 (NK1) receptor in the NTS. METHODS Immunohistochemical and fluorescent double-labeling techniques were employed to identify cystathionine beta-synthase (CBS) and c-Fos co-expressed positive neurons in the NTS during rat stress. Gastric motility curves were recorded by inserting a pressure-sensing balloon into the pylorus through the stomach fundus. Changes in gastric motility were observed before and after injecting different doses of NaHS (4 nmol and 8 nmol), physiological saline, Capsazepine (4 nmol) + NaHS (4 nmol), pyrrolidine dithiocarbamate (PDTC, 4 nmol) + NaHS (4 nmol), and L703606 (4 nmol) + NaHS (4 nmol). RESULTS We identified a significant increase in the co-expression of c-Fos and CBS positive neurons in the NTS after 1 h and 3 h of restraint water-immersion stress compared to the expressions observed in the control group. Intra-NTS injection of NaHS at different doses significantly inhibited gastric motility in rats (P < 0.01). However, injection of saline, first injection NF-κB inhibitor PDTC or transient receptor potential vanilloid 1 (TRPV1) antagonist Capsazepine or NK1 receptor blockers L703606 and then injection NaHS did not produce significant changes (P > 0.05). CONCLUSION NTS contains neurons co-expressing CBS and c-Fos, and the injection of NaHS into the NTS can suppress gastric motility in rats. This effect may be mediated by activating TRPV1 and NK1 receptors via the NF-κB channel.
Collapse
Affiliation(s)
- Hong-Zhao Sun
- College of Life Science, Qi Lu Normal University, Zhangqiu 250200, Shandong Province, China
| | - Chen-Yu Li
- College of Life Science, Qi Lu Normal University, Zhangqiu 250200, Shandong Province, China
| | - Yuan Shi
- College of Life Science, Qi Lu Normal University, Zhangqiu 250200, Shandong Province, China
| | - Jin-Jin Li
- College of Life Science, Qi Lu Normal University, Zhangqiu 250200, Shandong Province, China
| | - Yi-Ya Wang
- College of Life Science, Qi Lu Normal University, Zhangqiu 250200, Shandong Province, China
| | - Li-Na Han
- College of Life Science, Qi Lu Normal University, Zhangqiu 250200, Shandong Province, China
| | - Lu-Jie Zhu
- College of Life Science, Qi Lu Normal University, Zhangqiu 250200, Shandong Province, China
| | - Ya-Fei Zhang
- College of Life Science, Qi Lu Normal University, Zhangqiu 250200, Shandong Province, China
| |
Collapse
|
4
|
Gambino G, Gallo D, Covelo A, Ferraro G, Sardo P, Giglia G. TRPV1 channels in nitric oxide-mediated signalling: insight on excitatory transmission in rat CA1 pyramidal neurons. Free Radic Biol Med 2022; 191:128-136. [PMID: 36029909 DOI: 10.1016/j.freeradbiomed.2022.08.025] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/07/2022] [Revised: 08/13/2022] [Accepted: 08/15/2022] [Indexed: 11/18/2022]
Abstract
Nitric oxide (NO) is a fascinating signalling molecule implicated in a plethora of biological functions, especially at the synaptic level. Exploring neurotransmission in the hippocampus could be instrumental in the individuation of putative targets for nitric-oxide mediated neuromodulation, especially in terms of the potential repercussions on fundamental processes i.e. synaptic plasticity and excitability-related phenomena. Among these targets, endovanilloid signalling constitutes an object of study since Transient Receptors Vanilloid type 1 (TRPV1) channels possess a NO-sensitive gate modulating its activation. Also, NO has been referred to as a mediator for numerous endocannabinoid effects. Notwithstanding, the linkage between TRPV1 and NO systems in neuromodulation still remains elusive. To this end, we aim at investigating the involvement of TRPV1 in nitric oxide-mediated influence on hippocampal processes. Electrophysiological whole-cell recordings in CA1 pyramidal neurons were applied to evaluate excitatory neurotransmission in rat brain slices. Indeed, miniature excitatory postsynaptic currents (mEPSCs) were analysed upon pharmacological manipulation of TRPV1 and NO signalling pathways. In detail, only the administration of the specific TRPV1 exogenous agonist - capsaicin - reduced the frequency and amplitude of mEPSC similarly to the inhibitor of neuronal nitric oxide synthase (nNOS), 7-nitroindazole (7NI). In contrast, capsazepine, TRPV1 antagonist, does not influence excitatory transmission. The combined TRPV1 activation and nNOS blockade confirm the presence of a putative common mechanism. When we administered the endovanilloid-endocannabinoid ligand, i.e. anandamide, we unveiled a potentiation of neurotransmission that was selectively reverted by 7NI. Our data suggest that nitric oxide influences TRPV1 hippocampal signalling since these channels are not constitutively active, but can be "on-demand" activated to modulate excitation in CA1 pyramidal neurons, and that this effect is linked to nitric oxide production.
Collapse
Affiliation(s)
- Giuditta Gambino
- Department of Biomedicine, Neuroscience and Advanced Diagnostics (BIND), University of Palermo, Italy.
| | - Daniele Gallo
- Department of Biomedicine, Neuroscience and Advanced Diagnostics (BIND), University of Palermo, Italy
| | - Ana Covelo
- Institut National de la Santé et de la Recherche Médicale (INSERM), U1215 NeuroCentre Magendie, Bordeaux, France
| | - Giuseppe Ferraro
- Department of Biomedicine, Neuroscience and Advanced Diagnostics (BIND), University of Palermo, Italy
| | - Pierangelo Sardo
- Department of Biomedicine, Neuroscience and Advanced Diagnostics (BIND), University of Palermo, Italy
| | - Giuseppe Giglia
- Department of Biomedicine, Neuroscience and Advanced Diagnostics (BIND), University of Palermo, Italy
| |
Collapse
|
5
|
Khaksar S, Salimi M, Zeinoddini H, Naderi N. The Role of the Possible Receptors and Intracellular Pathways in Protective Effect of Exogenous Anandamide in Kindling Model of Epilepsy. Neurochem Res 2022; 47:1226-1242. [PMID: 35112235 DOI: 10.1007/s11064-021-03517-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2021] [Revised: 12/01/2021] [Accepted: 12/24/2021] [Indexed: 11/24/2022]
Abstract
In this research, the involvement of CB1 and TRPV1 receptors in the possible protective effects of anandamide were investigated in the kindling model of epilepsy. The basolateral amygdala of the rat brain was chosen to put stimulating electrodes. Semi-rapid kindling was induced by a repetitive sub-threshold stimulation for 5-9 consecutive days. There were seven groups, six of which were kindled and used for drug testing by intracerebroventricular (i.c.v.) microinjection. (i) Sham, (ii) control group received vehicles, (iii) anandamide (AEA; 100 ng/rat), (iv) capsazepine (TRPV1 antagonist; 100 ng/rat), (v) AM251 (CB1 antagonist; 100 ng/rat), (vi) AM251 + anandamide, and (vii) capsazepine + anandamide. The after-discharge duration, seizure duration, and stage five duration were measured in rats. Moreover, the expressions of the extracellular signal-regulated kinase (ERK) and the cAMP responsive element binding (CREB) proteins in the hippocampus were also studied. The anandamide-treated group showed a significant decrease in seizure scores, while no change was shown in seizure scores in the capsazepine- and AM251-treated groups compared with the control group. Co-administrations of either capsazepine + AEA or AM251 + AEA attenuated the protective effect of AEA against seizure. Furthermore, the group received AEA showed a decrease in the expressions of CREB and p-CREB possibly through the activation of the CB1 and TRPV1 receptors. Activation of CB1 and TRPV1 receptors might be involved in AEA anticonvulsant effect in kindling model of epilepsy. This effect could be due to suppression of CREB phosphorylation in hippocampal neurons.
Collapse
Affiliation(s)
- Sepideh Khaksar
- Department of Plant Sciences, Biological Sciences, Alzahra University, Tehran, Iran
| | - Mona Salimi
- Department of Physiology and Pharmacology, Pasteur Institute of Iran, Tehran, Iran
| | - Hadi Zeinoddini
- Department of Toxicology, School of Pharmacy, Shahid Beheshti University of Medical Sciences, No. 2660, Vali-e-Asr Ave, 1996835113, Tehran, Iran
| | - Nima Naderi
- Department of Toxicology, School of Pharmacy, Shahid Beheshti University of Medical Sciences, No. 2660, Vali-e-Asr Ave, 1996835113, Tehran, Iran. .,Neuroscience Research Center, Shahid Beheshti University of Medical Sciences, Tehran, Iran.
| |
Collapse
|
6
|
Sun H, Ding H, Shi Y, Li C, Jin H, Yang X, Chen Z, Tian P, Zhu J, Sun H. Exogenous Hydrogen Sulfide Within the Nucleus Ambiguus Inhibits Gastrointestinal Motility in Rats. Front Physiol 2020; 11:545184. [PMID: 33013478 PMCID: PMC7516268 DOI: 10.3389/fphys.2020.545184] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2020] [Accepted: 08/21/2020] [Indexed: 11/13/2022] Open
Abstract
Hydrogen sulfide (H2S) is a neuromodulator in the central nervous system. However, the physiological role of H2S in the nucleus ambiguus (NA) has rarely been reported. This research aimed to elucidate the role of H2S in the regulation of gastrointestinal motility in rats. Male Wistar rats were randomly assigned to sodium hydrosulfide (NaHS; 4 and 8 nmol) groups, physiological saline (PS) group, capsazepine (10 pmol) + NaHS (4 nmol) group, L703606 (4 nmol) + NaHS (4 nmol) group, and pyrrolidine dithiocarbamate (PDTC, 4 nmol) + NaHS (4 nmol) group. Gastrointestinal motility curves before and after the injection were recorded using a latex balloon attached with a pressure transducer, which was introduced into the pylorus through gastric fundus. The results demonstrated that NaHS (4 and 8 nmol), an exogenous H2S donor, remarkably suppressed gastrointestinal motility in the NA of rats (P < 0.01). The suppressive effect of NaHS on gastrointestinal motility could be prevented by capsazepine, a transient receptor potential vanilloid 1 (TRPV1) antagonist, and PDTC, a NF-κB inhibitor. However, the same amount of PS did not induce significant changes in gastrointestinal motility (P > 0.05). Our findings indicate that NaHS within the NA can remarkably suppress gastrointestinal motility in rats, possibly through TRPV1 channels and NF-κB-dependent mechanism.
Collapse
Affiliation(s)
- Hongzhao Sun
- School of Life Sciences, Qilu Normal University, Jinan, China
| | - Haikun Ding
- School of Life Sciences, Qilu Normal University, Jinan, China
| | - Yuan Shi
- School of Life Sciences, Qilu Normal University, Jinan, China
| | - Chenyu Li
- School of Life Sciences, Qilu Normal University, Jinan, China
| | - Haoran Jin
- School of Life Sciences, Qilu Normal University, Jinan, China
| | - Xiaoyue Yang
- School of Life Sciences, Qilu Normal University, Jinan, China
| | - Zhaosong Chen
- School of Life Sciences, Qilu Normal University, Jinan, China
| | - Pengpeng Tian
- School of Life Sciences, Qilu Normal University, Jinan, China
| | - Jianping Zhu
- Key Laboratory of Animal Resistance, School of Life Sciences, Shandong Normal University, Jinan, China
| | - Haiji Sun
- Key Laboratory of Animal Resistance, School of Life Sciences, Shandong Normal University, Jinan, China
| |
Collapse
|
7
|
Gambino G, Rizzo V, Giglia G, Ferraro G, Sardo P. Cannabinoids, TRPV and nitric oxide: the three ring circus of neuronal excitability. Brain Struct Funct 2019; 225:1-15. [PMID: 31792694 DOI: 10.1007/s00429-019-01992-9] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2019] [Accepted: 11/22/2019] [Indexed: 12/13/2022]
Abstract
Endocannabinoid system is considered a relevant player in the regulation of neuronal excitability, since it contributes to maintaining the balance of the synaptic ionic milieu. Perturbations to bioelectric conductances have been implicated in the pathophysiological processes leading to hyperexcitability and epileptic seizures. Cannabinoid influence on neurosignalling is exerted on classic receptor-mediated mechanisms or on further molecular targets. Among these, transient receptor potential vanilloid (TRPV) are ionic channels modulated by cannabinoids that are involved in the transduction of a plethora of stimuli and trigger fundamental downstream pathways in the post-synaptic site. In this review, we aim at providing a brief summary of the most recent data about the cross-talk between cannabinoid system and TRPV channels, drawing attention on their role on neuronal hyperexcitability. Then, we aim to unveil a plausible point of interaction between these neural signalling systems taking into consideration nitric oxide, a gaseous molecule inducing profound modifications to neural performances. From this novel perspective, we struggle to propose innovative cellular mechanisms in the regulation of hyperexcitability phenomena, with the goal of exploring plausible CB-related mechanisms underpinning epileptic seizures.
Collapse
Affiliation(s)
- Giuditta Gambino
- Department of Experimental Biomedicine, Neuroscience and Advanced Diagnostics (Bi.N.D.), Sezione di Fisiologia Umana G. Pagano, University of Palermo, Corso Tukory 129, Palermo, Italy.
| | - Valerio Rizzo
- Department of Experimental Biomedicine, Neuroscience and Advanced Diagnostics (Bi.N.D.), Sezione di Fisiologia Umana G. Pagano, University of Palermo, Corso Tukory 129, Palermo, Italy
| | - Giuseppe Giglia
- Department of Experimental Biomedicine, Neuroscience and Advanced Diagnostics (Bi.N.D.), Sezione di Fisiologia Umana G. Pagano, University of Palermo, Corso Tukory 129, Palermo, Italy
| | - Giuseppe Ferraro
- Department of Experimental Biomedicine, Neuroscience and Advanced Diagnostics (Bi.N.D.), Sezione di Fisiologia Umana G. Pagano, University of Palermo, Corso Tukory 129, Palermo, Italy
| | - Pierangelo Sardo
- Department of Experimental Biomedicine, Neuroscience and Advanced Diagnostics (Bi.N.D.), Sezione di Fisiologia Umana G. Pagano, University of Palermo, Corso Tukory 129, Palermo, Italy
| |
Collapse
|
8
|
Molinas AJR, Desmoulins LD, Hamling BV, Butcher SM, Anwar IJ, Miyata K, Enix CL, Dugas CM, Satou R, Derbenev AV, Zsombok A. Interaction between TRPV1-expressing neurons in the hypothalamus. J Neurophysiol 2019; 121:140-151. [PMID: 30461371 PMCID: PMC6383661 DOI: 10.1152/jn.00004.2018] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2018] [Revised: 10/29/2018] [Accepted: 11/14/2018] [Indexed: 02/08/2023] Open
Abstract
Transient receptor potential vanilloid type 1 (TRPV1) is a ligand-gated ion channel expressed in the peripheral and central nervous systems. TRPV1-dependent mechanisms take part in a wide range of physiological and pathophysiological pathways including the regulation of homeostatic functions. TRPV1 expression in the hypothalamus has been described as well as evidence that TRPV1-dependent excitatory inputs to hypothalamic preautonomic neurons are diminished in diabetic conditions. Here we aimed to determine the functional expression of TRPV1 in two hypothalamic nuclei known to be involved in the central control of metabolism and to test the hypothesis that TRPV1-expressing neurons receive TRPV1-expressing inputs. A mouse model (TRPV1Cre/tdTom) was generated to identify TRPV1-expressing cells and determine the cellular properties of TRPV1-expressing neurons in adult mice. Our study demonstrated the functional expression of TRPV1 in the dorsomedial hypothalamic nucleus and paraventricular nucleus in adult mice. Our findings revealed that a subset of TRPV1Cre/tdTom neurons receive TRPV1-expressing excitatory inputs, indicating direct interaction between TRPV1-expressing neurons. In addition, astrocytes likely play a role in the modulation of TRPV1-expressing neurons. In summary, this study identified specific hypothalamic regions where TRPV1 is expressed and functional in adult mice and the existence of direct connections between TRPV1Cre/tdTom neurons. NEW & NOTEWORTHY Transient receptor potential vanilloid type 1 (TRPV1) is expressed in the hypothalamus, and TRPV1-dependent regulation of preautonomic neurons is decreased in hyperglycemic conditions. Our study demonstrated functional expression of TRPV1 in two hypothalamic nuclei involved in the control of energy homeostasis. Our results also revealed that a subset of TRPV1-expressing neurons receive TRPV1-expressing excitatory inputs. These findings suggest direct interaction between TRPV1-expressing neurons.
Collapse
Affiliation(s)
- Adrien J R Molinas
- Department of Physiology, School of Medicine, Tulane University , New Orleans, Louisiana
| | - Lucie D Desmoulins
- Department of Physiology, School of Medicine, Tulane University , New Orleans, Louisiana
| | - Brooke V Hamling
- Department of Physiology, School of Medicine, Tulane University , New Orleans, Louisiana
- Neuroscience Program, Brain Institute, Tulane University , New Orleans, Louisiana
| | - Sierra M Butcher
- Department of Physiology, School of Medicine, Tulane University , New Orleans, Louisiana
- Neuroscience Program, Brain Institute, Tulane University , New Orleans, Louisiana
| | - Imran J Anwar
- Department of Physiology, School of Medicine, Tulane University , New Orleans, Louisiana
| | - Kayoko Miyata
- Department of Physiology, School of Medicine, Tulane University , New Orleans, Louisiana
| | - Courtney L Enix
- Department of Physiology, School of Medicine, Tulane University , New Orleans, Louisiana
| | - Courtney M Dugas
- Department of Physiology, School of Medicine, Tulane University , New Orleans, Louisiana
| | - Ryousuke Satou
- Department of Physiology, School of Medicine, Tulane University , New Orleans, Louisiana
| | - Andrei V Derbenev
- Department of Physiology, School of Medicine, Tulane University , New Orleans, Louisiana
- Neuroscience Program, Brain Institute, Tulane University , New Orleans, Louisiana
| | - Andrea Zsombok
- Department of Physiology, School of Medicine, Tulane University , New Orleans, Louisiana
- Neuroscience Program, Brain Institute, Tulane University , New Orleans, Louisiana
| |
Collapse
|
9
|
Overactivity of Liver-Related Neurons in the Paraventricular Nucleus of the Hypothalamus: Electrophysiological Findings in db/db Mice. J Neurosci 2017; 37:11140-11150. [PMID: 29038244 DOI: 10.1523/jneurosci.1706-17.2017] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2017] [Revised: 09/11/2017] [Accepted: 10/03/2017] [Indexed: 12/11/2022] Open
Abstract
Preautonomic neurons in the paraventricular nucleus (PVN) of the hypothalamus play a large role in the regulation of hepatic functions via the autonomic nervous system. Activation of hepatic sympathetic nerves increases glucose and lipid metabolism and contributes to the elevated hepatic glucose production observed in the type 2 diabetic condition. This augmented sympathetic output could originate from altered activity of liver-related PVN neurons. Remarkably, despite the importance of the brain-liver pathway, the cellular properties of liver-related neurons are not known. In this study, we provide the first evidence of overall activity of liver-related PVN neurons. Liver-related PVN neurons were identified with a retrograde, trans-synaptic, viral tracer in male lean and db/db mice and whole-cell patch-clamp recordings were conducted. In db/db mice, the majority of liver-related PVN neurons fired spontaneously; whereas, in lean mice the majority of liver-related PVN neurons were silent, indicating that liver-related PVN neurons are more active in db/db mice. Persistent, tonic inhibition was identified in liver-related PVN neurons; although, the magnitude of tonic inhibitory control was not different between lean and db/db mice. In addition, our study revealed that the transient receptor potential vanilloid type 1-dependent increase of excitatory neurotransmission was reduced in liver-related PVN neurons of db/db mice. These findings demonstrate plasticity of liver-related PVN neurons and a shift toward excitation in a diabetic mouse model. Our study suggests altered autonomic circuits at the level of the PVN, which can contribute to autonomic dysfunction and dysregulation of neural control of hepatic functions including glucose metabolism.SIGNIFICANCE STATEMENT A growing body of evidence suggests the importance of the autonomic control in the regulation of hepatic metabolism, which plays a major role in the development and progression of type 2 diabetes mellitus. Despite the importance of the brain-liver pathway, the overall activity of liver-related neurons in control and diabetic conditions is not known. This is a significant gap in knowledge, which prevents developing strategies to improve glucose homeostasis via altering the brain-liver pathway. One of the key findings of our study is the overall shift toward excitation in liver-related hypothalamic neurons in the diabetic condition. This overactivity may be one of the underlying mechanisms of elevated sympathetic activity known in metabolically compromised patients and animal models.
Collapse
|
10
|
Nongenomic Glucocorticoid Suppression of a Postsynaptic Potassium Current via Emergent Autocrine Endocannabinoid Signaling in Hypothalamic Neuroendocrine Cells following Chronic Dehydration. eNeuro 2017; 4:eN-NWR-0216-17. [PMID: 28966975 PMCID: PMC5617081 DOI: 10.1523/eneuro.0216-17.2017] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2017] [Revised: 08/19/2017] [Accepted: 08/22/2017] [Indexed: 11/21/2022] Open
Abstract
Glucocorticoids rapidly stimulate endocannabinoid synthesis and modulation of synaptic transmission in hypothalamic neuroendocrine cells via a nongenomic signaling mechanism. The endocannabinoid actions are synapse-constrained by astrocyte restriction of extracellular spatial domains. Exogenous cannabinoids have been shown to modulate postsynaptic potassium currents, including the A-type potassium current (IA), in different cell types. The activity of magnocellular neuroendocrine cells is shaped by a prominent IA. We tested for a rapid glucocorticoid modulation of the postsynaptic IK and IA in magnocellular neuroendocrine cells of the hypothalamic paraventricular nucleus (PVN) using whole-cell recordings in rat brain slices. Application of the synthetic glucocorticoid dexamethasone (Dex) had no rapid effect on the IK or IA amplitude, voltage dependence, or kinetics in magnocellular neurons in slices from untreated rats. In magnocellular neurons from salt-loaded rats, however, Dex application caused a rapid suppression of the IA and a depolarizing shift in IA voltage dependence. Exogenously applied endocannabinoids mimicked the rapid Dex modulation of the IA, and CB1 receptor antagonists and agonists blocked and occluded the Dex-induced changes in the IA, respectively, suggesting an endocannabinoid dependence of the rapid glucocorticoid effect. Preincubation of control slices in a gliotoxin resulted in the partial recapitulation of the glucocorticoid-induced rapid suppression of the IA. These findings demonstrate a glucocorticoid suppression of the postsynaptic IA in PVN magnocellular neurons via an autocrine endocannabinoid-dependent mechanism following chronic dehydration, and suggest a possible role for astrocytes in the control of the autocrine endocannabinoid actions.
Collapse
|
11
|
Zhong W, Picca AJ, Lee AS, Darmani NA. Ca2+ signaling and emesis: Recent progress and new perspectives. Auton Neurosci 2017; 202:18-27. [DOI: 10.1016/j.autneu.2016.07.006] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2016] [Revised: 07/21/2016] [Accepted: 07/22/2016] [Indexed: 02/07/2023]
|
12
|
Boychuk CR, Smith BN. Glutamatergic drive facilitates synaptic inhibition of dorsal vagal motor neurons after experimentally induced diabetes in mice. J Neurophysiol 2016; 116:1498-506. [PMID: 27385796 DOI: 10.1152/jn.00325.2016] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2016] [Accepted: 07/01/2016] [Indexed: 12/31/2022] Open
Abstract
The role of central regulatory circuits in modulating diabetes-associated glucose dysregulation has only recently been under rigorous investigation. One brain region of interest is the dorsal motor nucleus of the vagus (DMV), which contains preganglionic parasympathetic motor neurons that regulate subdiaphragmatic visceral function. Previous research has demonstrated that glutamatergic and GABAergic neurotransmission are independently remodeled after chronic hyperglycemia/hypoinsulinemia. However, glutamatergic circuitry within the dorsal brain stem impinges on GABAergic regulation of the DMV. The present study investigated the role of glutamatergic neurotransmission in synaptic GABAergic control of DMV neurons after streptozotocin (STZ)-induced hyperglycemia/hypoinsulinemia by using electrophysiological recordings in vitro. The frequency of spontaneous inhibitory postsynaptic currents (sIPSCs) was elevated in DMV neurons from STZ-treated mice. The effect was abolished in the presence of the ionotropic glutamate receptor blocker kynurenic acid or the sodium channel blocker tetrodotoxin, suggesting that after STZ-induced hyperglycemia/hypoinsulinemia, increased glutamatergic receptor activity occurs at a soma-dendritic location on local GABA neurons projecting to the DMV. Although sIPSCs in DMV neurons normally demonstrated considerable amplitude variability, this variability was significantly increased after STZ-induced hyperglycemia/hypoinsulinemia. The elevated amplitude variability was not related to changes in quantal release, but rather correlated with significantly elevated frequency of sIPSCs in these mice. Taken together, these findings suggest that GABAergic regulation of central vagal circuitry responsible for the regulation of energy homeostasis undergoes complex functional reorganization after several days of hyperglycemia/hypoinsulinemia, including both glutamate-dependent and -independent forms of plasticity.
Collapse
Affiliation(s)
- Carie R Boychuk
- Department of Physiology, University of Kentucky College of Medicine, Lexington, Kentucky
| | - Bret N Smith
- Department of Physiology, University of Kentucky College of Medicine, Lexington, Kentucky
| |
Collapse
|
13
|
Abstract
A large body of research has been dedicated to the effects of gastrointestinal peptides on vagal afferent fibres, yet multiple lines of evidence indicate that gastrointestinal peptides also modulate brainstem vagal neurocircuitry, and that this modulation has a fundamental role in the physiology and pathophysiology of the upper gastrointestinal tract. In fact, brainstem vagovagal neurocircuits comprise highly plastic neurons and synapses connecting afferent vagal fibres, second order neurons of the nucleus tractus solitarius (NTS), and efferent fibres originating in the dorsal motor nucleus of the vagus (DMV). Neuronal communication between the NTS and DMV is regulated by the presence of a variety of inputs, both from within the brainstem itself as well as from higher centres, which utilize an array of neurotransmitters and neuromodulators. Because of the circumventricular nature of these brainstem areas, circulating hormones can also modulate the vagal output to the upper gastrointestinal tract. This Review summarizes the organization and function of vagovagal reflex control of the upper gastrointestinal tract, presents data on the plasticity within these neurocircuits after stress, and discusses the gastrointestinal dysfunctions observed in Parkinson disease as examples of physiological adjustment and maladaptation of these reflexes.
Collapse
|
14
|
Schaich CL, Grabenauer M, Thomas BF, Shaltout HA, Gallagher PE, Howlett AC, Diz DI. Medullary Endocannabinoids Contribute to the Differential Resting Baroreflex Sensitivity in Rats with Altered Brain Renin-Angiotensin System Expression. Front Physiol 2016; 7:207. [PMID: 27375489 PMCID: PMC4899471 DOI: 10.3389/fphys.2016.00207] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2015] [Accepted: 05/22/2016] [Indexed: 11/13/2022] Open
Abstract
CB1 cannabinoid receptors are expressed on vagal afferent fibers and neurons within the solitary tract nucleus (NTS), providing anatomical evidence for their role in arterial baroreflex modulation. To better understand the relationship between the brain renin-angiotensin system (RAS) and endocannabinoid expression within the NTS, we measured dorsal medullary endocannabinoid tissue content and the effects of CB1 receptor blockade at this brain site on cardiac baroreflex sensitivity (BRS) in ASrAOGEN rats with low glial angiotensinogen, normal Sprague-Dawley rats and (mRen2)27 rats with upregulated brain RAS expression. Mass spectrometry revealed higher levels of the endocannabinoid 2-arachidonoylglycerol in (mRen2)27 compared to ASrAOGEN rats (2.70 ± 0.28 vs. 1.17 ± 0.09 ng/mg tissue; P < 0.01), while Sprague-Dawley rats had intermediate content (1.85 ± 0.27 ng/mg tissue). Microinjection of the CB1receptor antagonist SR141716A (36 pmol) into the NTS did not change cardiac BRS in anesthetized Sprague-Dawley rats (1.04 ± 0.05 ms/mmHg baseline vs. 1.17 ± 0.11 ms/mmHg after 10 min). However, SR141716A in (mRen2)27 rats dose-dependently improved BRS in this strain: 0.36 pmol of SR141716A increased BRS from 0.43 ± 0.03 to 0.71 ± 0.04 ms/mmHg (P < 0.001), and 36 pmol of SR141716A increased BRS from 0.47 ± 0.02 to 0.94 ± 0.10 ms/mmHg (P < 0.01). In contrast, 0.36 pmol (1.50 ± 0.12 vs. 0.86 ± 0.08 ms/mmHg; P < 0.05) and 36 pmol (1.38 ± 0.16 vs. 0.46 ± 0.003 ms/mmHg; P < 0.01) of SR141716A significantly reduced BRS in ASrAOGEN rats. These observations reveal differential dose-related effects of the brain endocannabinoid system that influence cardiovagal BRS in animals with genetic alterations in the brain RAS.
Collapse
Affiliation(s)
- Chris L Schaich
- Department of Physiology and Pharmacology and Hypertension and Vascular Research Center, Wake Forest School of Medicine Winston-Salem, NC, USA
| | - Megan Grabenauer
- Department of Physiology and Pharmacology and Hypertension and Vascular Research Center, Wake Forest School of MedicineWinston-Salem, NC, USA; Analytical Chemistry and Pharmaceutics, RTI InternationalResearch Triangle Park, NC, USA
| | - Brian F Thomas
- Department of Physiology and Pharmacology and Hypertension and Vascular Research Center, Wake Forest School of MedicineWinston-Salem, NC, USA; Analytical Chemistry and Pharmaceutics, RTI InternationalResearch Triangle Park, NC, USA
| | - Hossam A Shaltout
- Department of Physiology and Pharmacology and Hypertension and Vascular Research Center, Wake Forest School of MedicineWinston-Salem, NC, USA; Department of Obstetrics and Gynecology, Wake Forest School of MedicineWinston-Salem, NC, USA
| | - Patricia E Gallagher
- Department of Physiology and Pharmacology and Hypertension and Vascular Research Center, Wake Forest School of Medicine Winston-Salem, NC, USA
| | - Allyn C Howlett
- Department of Physiology and Pharmacology and Hypertension and Vascular Research Center, Wake Forest School of Medicine Winston-Salem, NC, USA
| | - Debra I Diz
- Department of Physiology and Pharmacology and Hypertension and Vascular Research Center, Wake Forest School of Medicine Winston-Salem, NC, USA
| |
Collapse
|
15
|
Derbenev AV, Zsombok A. Potential therapeutic value of TRPV1 and TRPA1 in diabetes mellitus and obesity. Semin Immunopathol 2016; 38:397-406. [PMID: 26403087 PMCID: PMC4808497 DOI: 10.1007/s00281-015-0529-x] [Citation(s) in RCA: 60] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2015] [Accepted: 09/09/2015] [Indexed: 11/30/2022]
Abstract
Diabetes mellitus and obesity, which is a major risk factor in the development of type 2 diabetes mellitus, have reached epidemic proportions worldwide including the USA. The current statistics and forecasts, both short- and long-term, are alarming and predict severe problems in the near future. Therefore, there is a race for developing new compounds, discovering new receptors, or finding alternative solutions to prevent and/or treat the symptoms and complications related to obesity and diabetes mellitus. It is well demonstrated that members of the transient receptor potential (TRP) superfamily play a crucial role in a variety of biological functions both in health and disease. In the recent years, transient receptor potential vanilloid type 1 (TRPV1) and transient receptor potential ankyrin 1 (TRPA1) were shown to have beneficial effects on whole body metabolism including glucose homeostasis. TRPV1 and TRPA1 have been associated with control of weight, pancreatic function, hormone secretion, thermogenesis, and neuronal function, which suggest a potential therapeutic value of these channels. This review summarizes recent findings regarding TRPV1 and TRPA1 in association with whole body metabolism with emphasis on obese and diabetic conditions.
Collapse
Affiliation(s)
- Andrei V Derbenev
- Department of Physiology, School of Medicine, Tulane University, 1430 Tulane Ave., New Orleans, LA, 70112, USA
| | - Andrea Zsombok
- Department of Physiology, School of Medicine, Tulane University, 1430 Tulane Ave., New Orleans, LA, 70112, USA.
- Department of Medicine, Endocrinology Section, School of Medicine, Tulane University, 1430 Tulane Ave., New Orleans, LA, 70112, USA.
| |
Collapse
|
16
|
Presynaptic ionotropic glutamate receptors modulate GABA release in the mouse dorsal motor nucleus of the vagus. Neuroscience 2015; 308:95-105. [PMID: 26343294 DOI: 10.1016/j.neuroscience.2015.09.009] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2015] [Revised: 08/25/2015] [Accepted: 09/02/2015] [Indexed: 11/21/2022]
Abstract
Regulation of GABA release in the dorsal motor nucleus of the vagus (DMV) potently influences vagal output to the viscera. The presence of functional ionotropic glutamate receptors (iGluRs) on GABAergic terminals that rapidly alter GABA release onto DMV motor neurons has been suggested previously, but the receptor subtypes contributing to the response are unknown. We examined the effect of selective activation and inhibition of iGluRs on tetrodotoxin-insensitive, miniature inhibitory postsynaptic currents (mIPSCs) in DMV neurons using patch-clamp recordings in brainstem slices from mice. Capsaicin, which activates transient receptor potential vanilloid type 1 (TRPV1) receptors and increases mIPSC frequency in the DMV via an iGluR-mediated, heterosynaptic mechanism, was also applied to assess GABA release subsequent to capsaicin-stimulated glutamate release. Application of glutamate, N-methyl-d-aspartate (NMDA), or kainic acid (KA), but not AMPA, resulted in increased mIPSC frequency in most neurons. Inhibition of AMPA/KA receptors reduced mIPSC frequency, but selective antagonism of AMPA receptors did not alter GABA release, implicating the presence of presynaptic KA receptors on GABAergic terminals. Whereas NMDA application increased mIPSC frequency, blocking NMDA receptors was without effect, indicating that presynaptic NMDA receptors were present, but not activated by ambient glutamate levels in the slice. The effect of NMDA was prevented by AMPA/KA receptor blockade, suggesting indirect involvement of NMDA receptors. The stimulatory effect of capsaicin on GABA release was prevented when AMPA/KA or NMDA, but not AMPA receptors were blocked. Results of these studies indicate that presynaptic NMDAR and KA receptors regulate GABA release in the DMV, representing a heterosynaptic arrangement for rapidly modulating parasympathetic output, especially when synaptic excitation is elevated.
Collapse
|
17
|
Kentish SJ, Frisby CL, Kritas S, Li H, Hatzinikolas G, O'Donnell TA, Wittert GA, Page AJ. TRPV1 Channels and Gastric Vagal Afferent Signalling in Lean and High Fat Diet Induced Obese Mice. PLoS One 2015; 10:e0135892. [PMID: 26285043 PMCID: PMC4540489 DOI: 10.1371/journal.pone.0135892] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2015] [Accepted: 07/28/2015] [Indexed: 12/31/2022] Open
Abstract
Aim Within the gastrointestinal tract vagal afferents play a role in control of food intake and satiety signalling. Activation of mechanosensitive gastric vagal afferents induces satiety. However, gastric vagal afferent responses to mechanical stretch are reduced in high fat diet mice. Transient receptor potential vanilloid 1 channels (TRPV1) are expressed in vagal afferents and knockout of TRPV1 reduces gastro-oesophageal vagal afferent responses to stretch. We aimed to determine the role of TRPV1 on gastric vagal afferent mechanosensitivity and food intake in lean and HFD-induced obese mice. Methods TRPV1+/+ and -/- mice were fed either a standard laboratory diet or high fat diet for 20wks. Gastric emptying of a solid meal and gastric vagal afferent mechanosensitivity was determined. Results Gastric emptying was delayed in high fat diet mice but there was no difference between TRPV1+/+ and -/- mice on either diet. TRPV1 mRNA expression in whole nodose ganglia of TRPV1+/+ mice was similar in both dietary groups. The TRPV1 agonist N-oleoyldopamine potentiated the response of tension receptors in standard laboratory diet but not high fat diet mice. Food intake was greater in the standard laboratory diet TRPV1-/- compared to TRPV1+/+ mice. This was associated with reduced response of tension receptors to stretch in standard laboratory diet TRPV1-/- mice. Tension receptor responses to stretch were decreased in high fat diet compared to standard laboratory diet TRPV1+/+ mice; an effect not observed in TRPV1-/- mice. Disruption of TRPV1 had no effect on the response of mucosal receptors to mucosal stroking in mice on either diet. Conclusion TRPV1 channels selectively modulate gastric vagal afferent tension receptor mechanosensitivity and may mediate the reduction in gastric vagal afferent mechanosensitivity in high fat diet-induced obesity.
Collapse
Affiliation(s)
- Stephen J Kentish
- Centre for Nutrition and Gastrointestinal Diseases, Discipline of Medicine, University of Adelaide, Adelaide, South Australia, Australia; South Australian Health and Medical Research Institute (SAHMRI), Adelaide, South Australia, Australia
| | - Claudine L Frisby
- Centre for Nutrition and Gastrointestinal Diseases, Discipline of Medicine, University of Adelaide, Adelaide, South Australia, Australia; South Australian Health and Medical Research Institute (SAHMRI), Adelaide, South Australia, Australia
| | - Stamatiki Kritas
- Women's & Children's Hospital, Adelaide, South Australia, Australia
| | - Hui Li
- Centre for Nutrition and Gastrointestinal Diseases, Discipline of Medicine, University of Adelaide, Adelaide, South Australia, Australia; South Australian Health and Medical Research Institute (SAHMRI), Adelaide, South Australia, Australia
| | - George Hatzinikolas
- Centre for Nutrition and Gastrointestinal Diseases, Discipline of Medicine, University of Adelaide, Adelaide, South Australia, Australia; South Australian Health and Medical Research Institute (SAHMRI), Adelaide, South Australia, Australia
| | - Tracey A O'Donnell
- Centre for Nutrition and Gastrointestinal Diseases, Discipline of Medicine, University of Adelaide, Adelaide, South Australia, Australia; South Australian Health and Medical Research Institute (SAHMRI), Adelaide, South Australia, Australia
| | - Gary A Wittert
- Centre for Nutrition and Gastrointestinal Diseases, Discipline of Medicine, University of Adelaide, Adelaide, South Australia, Australia; South Australian Health and Medical Research Institute (SAHMRI), Adelaide, South Australia, Australia; Royal Adelaide Hospital, Adelaide, South Australia, Australia
| | - Amanda J Page
- Centre for Nutrition and Gastrointestinal Diseases, Discipline of Medicine, University of Adelaide, Adelaide, South Australia, Australia; South Australian Health and Medical Research Institute (SAHMRI), Adelaide, South Australia, Australia; Royal Adelaide Hospital, Adelaide, South Australia, Australia
| |
Collapse
|
18
|
Browning KN, Travagli RA. Central nervous system control of gastrointestinal motility and secretion and modulation of gastrointestinal functions. Compr Physiol 2015; 4:1339-68. [PMID: 25428846 DOI: 10.1002/cphy.c130055] [Citation(s) in RCA: 322] [Impact Index Per Article: 35.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Although the gastrointestinal (GI) tract possesses intrinsic neural plexuses that allow a significant degree of autonomy over GI functions, the central nervous system (CNS) provides extrinsic neural inputs that regulate, modulate, and control these functions. While the intestines are capable of functioning in the absence of extrinsic inputs, the stomach and esophagus are much more dependent upon extrinsic neural inputs, particularly from parasympathetic and sympathetic pathways. The sympathetic nervous system exerts a predominantly inhibitory effect upon GI muscle and provides a tonic inhibitory influence over mucosal secretion while, at the same time, regulates GI blood flow via neurally mediated vasoconstriction. The parasympathetic nervous system, in contrast, exerts both excitatory and inhibitory control over gastric and intestinal tone and motility. Although GI functions are controlled by the autonomic nervous system and occur, by and large, independently of conscious perception, it is clear that the higher CNS centers influence homeostatic control as well as cognitive and behavioral functions. This review will describe the basic neural circuitry of extrinsic inputs to the GI tract as well as the major CNS nuclei that innervate and modulate the activity of these pathways. The role of CNS-centered reflexes in the regulation of GI functions will be discussed as will modulation of these reflexes under both physiological and pathophysiological conditions. Finally, future directions within the field will be discussed in terms of important questions that remain to be resolved and advances in technology that may help provide these answers.
Collapse
Affiliation(s)
- Kirsteen N Browning
- Department of Neural and Behavioral Sciences, Penn State College of Medicine, Hershey, Pennsylvania
| | | |
Collapse
|
19
|
Enhanced NMDA receptor-mediated modulation of excitatory neurotransmission in the dorsal vagal complex of streptozotocin-treated, chronically hyperglycemic mice. PLoS One 2015; 10:e0121022. [PMID: 25799386 PMCID: PMC4370733 DOI: 10.1371/journal.pone.0121022] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2014] [Accepted: 02/09/2015] [Indexed: 11/19/2022] Open
Abstract
A variety of metabolic disorders, including complications experienced by diabetic patients, have been linked to altered neural activity in the dorsal vagal complex. This study tested the hypothesis that augmentation of N-Methyl-D-Aspartate (NMDA) receptor-mediated responses in the vagal complex contributes to increased glutamate release in the dorsal motor nucleus of the vagus nerve (DMV) in mice with streptozotocin-induced chronic hyperglycemia (i.e., hyperglycemic mice), a model of type 1 diabetes. Antagonism of NMDA receptors with AP-5 (100 μM) suppressed sEPSC frequency in vagal motor neurons recorded in vitro, confirming that constitutively active NMDA receptors regulate glutamate release in the DMV. There was a greater relative effect of NMDA receptor antagonism in hyperglycemic mice, suggesting that augmented NMDA effects occur in neurons presynaptic to the DMV. Effects of NMDA receptor blockade on mEPSC frequency were equivalent in control and diabetic mice, suggesting that differential effects on glutamate release were due to altered NMDA function in the soma-dendritic membrane of intact afferent neurons. Application of NMDA (300 μM) resulted in greater inward current and current density in NTS neurons recorded from hyperglycemic than control mice, particularly in glutamatergic NTS neurons identified by single-cell RT-PCR for VGLUT2. Overall expression of NR1 protein and message in the dorsal vagal complex were not different between the two groups. Enhanced postsynaptic NMDA responsiveness of glutamatergic NTS neurons is consistent with tonically-increased glutamate release in the DMV in mice with chronic hyperglycemia. Functional augmentation of NMDA-mediated responses may serve as a physiological counter-regulatory mechanism to control pathological disturbances of homeostatic autonomic function in type 1 diabetes.
Collapse
|
20
|
Compartment-specific modulation of GABAergic synaptic transmission by TRPV1 channels in the dentate gyrus. J Neurosci 2015; 34:16621-9. [PMID: 25505315 DOI: 10.1523/jneurosci.3635-14.2014] [Citation(s) in RCA: 47] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
The transient receptor potential TRPV1 or vanilloid receptor is a nonselective ligand-gated channel highly expressed in primary sensory neurons where it mediates nociception. TRPV1 is also expressed in the brain where its activation depresses excitatory synaptic transmission. Whether TRPV1 also regulates inhibitory synapses in the brain is unclear. Here, using a combination of pharmacology, electrophysiology, and an in vivo knockdown strategy, we report that TRPV1 activation by capsaicin or by the endocannabinoid anandamide depresses somatic, but not dendritic inhibitory transmission in both rat and mouse dentate gyrus. The effect on somatic inhibition was absent in TRPV1 knock-out mice and was also eliminated by two different TRPV1 shRNAs expressed in dentate granule cells, strongly supporting a functional role for TRPV1 in modulating GABAergic synaptic function. Moreover, TRPV1-mediated depression occurs independently of GABA release, requires postsynaptic Ca(2+) rise and activation of calcineurin, and is likely due to clathrin-dependent internalization of GABA receptors. Altogether, these findings reveal a novel form of compartment-specific regulation whereby TRPV1 channels can modify synaptic function in the brain.
Collapse
|
21
|
Exposure to Allergen Causes Changes in NTS Neural Activities after Intratracheal Capsaicin Application, in Endocannabinoid Levels and in the Glia Morphology of NTS. BIOMED RESEARCH INTERNATIONAL 2015; 2015:980983. [PMID: 25866824 PMCID: PMC4383154 DOI: 10.1155/2015/980983] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/16/2014] [Revised: 09/25/2014] [Accepted: 10/06/2014] [Indexed: 11/17/2022]
Abstract
Allergen exposure may induce changes in the brainstem secondary neurons, with neural sensitization of the nucleus solitary tract (NTS), which in turn can be considered one of the causes of the airway hyperresponsiveness, a characteristic feature of asthma. We evaluated neurofunctional, morphological, and biochemical changes in the NTS of naive or sensitized rats. To evaluate the cell firing activity of NTS, in vivo electrophysiological experiments were performed before and after capsaicin challenge in sensitized or naive rats. Immunohistochemical studies, endocannabinoid, and palmitoylethanolamide quantification in the NTS were also performed. This study provides evidence that allergen sensitization in the NTS induced: (1) increase in the neural firing response to intratracheal capsaicin application, (2) increase of endocannabinoid anandamide and palmitoylethanolamide, a reduction of 2-arachidonoylglycerol levels in the NTS, (3) glial cell activation, and (4) prevention by a Group III metabotropic glutamate receptor activation of neural firing response to intratracheal application of capsaicin in both naïve and sensitized rats. Therefore, normalization of ovalbumin-induced NTS neural sensitization could open up the prospect of new treatments based on the recovery of specific brain nuclei function and for extensive studies on acute or long-term efficacy of selective mGlu ligand, in models of bronchial hyperreactivity.
Collapse
|
22
|
Kentish SJ, Page AJ. The role of gastrointestinal vagal afferent fibres in obesity. J Physiol 2014; 593:775-86. [PMID: 25433079 DOI: 10.1113/jphysiol.2014.278226] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2014] [Accepted: 11/21/2014] [Indexed: 12/16/2022] Open
Abstract
Gastrointestinal (GI) vagal afferents are a key mediatory of food intake. Through a balance of responses to chemical and mechanical stimuli food intake can be tightly controlled via the ascending satiety signals initiated in the GI tract. However, vagal responses to both mechanical and chemical stimuli are modified in diet-induced obesity (DIO). Much of the research to date whilst in relatively isolated/controlled circumstances indicates a shift between a balance of orexigenic and anorexigenic vagal signals to blunted anorexigenic and potentiated orexigenic capacity. Although the mechanism responsible for the DIO shift in GI vagal afferent signalling is unknown, one possible contributing factor is the gut microbiota. Nevertheless, whatever the mechanism, the observed changes in gastrointestinal vagal afferent signalling may underlie the pathophysiological changes in food consumption that are pivotal for the development and maintenance of obesity.
Collapse
Affiliation(s)
- Stephen J Kentish
- Discipline of Medicine, University of Adelaide, Frome Road, Adelaide, SA, 5005, Australia; Royal Adelaide Hospital, North Terrace, Adelaide, SA, 5000, Australia
| | | |
Collapse
|
23
|
Xu H, Boychuk JA, Boychuk CR, Uteshev VV, Smith BN. Nicotine enhances inhibition of mouse vagal motor neurons by modulating excitability of premotor GABAergic neurons in the nucleus tractus solitarii. J Neurophysiol 2014; 113:1165-74. [PMID: 25429117 DOI: 10.1152/jn.00614.2014] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The caudal nucleus of the solitary tract (NTS) serves as the site of the first synapse for visceral sensory inputs to the central nervous system. The NTS sends functional projections to multiple brain nuclei, with gastric-related projections primarily targeting the dorsal motor nucleus of the vagus (DMV). Previous studies have demonstrated that the majority of caudal NTS neurons that project to the DMV respond robustly to nicotine and express nicotinic acetylcholine receptors (nAChRs). However, the cytochemical identity and relationship with specific viscera of DMV-projecting, nicotine-responsive caudal NTS neurons have not been determined. The present study used transgenic mice that express enhanced green fluorescent protein (EGFP) under a GAD67 promoter in a subset of GABAergic neurons, in vivo retrograde pseudorabies viral labeling to identify gastric-related vagal complex neurons, and patch-clamp electrophysiology in acute brain stem slices to test the hypothesis that gastric-related and GABAergic inhibitory synaptic input to the DMV from the caudal NTS is under a robust modulatory control by nAChRs. Our results suggest that activation of nAChRs in the caudal NTS, but not DMV, potentiates GABAergic, but not glutamatergic, input to the DMV. Gastric-related caudal NTS and DMV neurons are directly involved in this nicotine-sensitive circuitry. Understanding the central patterns of nicotinic modulation of visceral sensory-motor circuitry may help develop therapeutic interventions to restore autonomic homeostasis in patients with autonomic impairments.
Collapse
Affiliation(s)
- Hong Xu
- Department of Physiology, College of Medicine, University of Kentucky, Lexington, Kentucky; and
| | - Jeffery A Boychuk
- Department of Physiology, College of Medicine, University of Kentucky, Lexington, Kentucky; and
| | - Carie R Boychuk
- Department of Physiology, College of Medicine, University of Kentucky, Lexington, Kentucky; and
| | - Victor V Uteshev
- Department of Pharmacology and Neuroscience, University of North Texas Health Science Center, Fort Worth, Texas
| | - Bret N Smith
- Department of Physiology, College of Medicine, University of Kentucky, Lexington, Kentucky; and
| |
Collapse
|
24
|
Zsombok A, Jiang Y, Gao H, Anwar IJ, Rezai-Zadeh K, Enix CL, Münzberg H, Derbenev AV. Regulation of leptin receptor-expressing neurons in the brainstem by TRPV1. Physiol Rep 2014; 2:2/9/e12160. [PMID: 25263209 PMCID: PMC4270226 DOI: 10.14814/phy2.12160] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
The central nervous system plays a critical role in the regulation of feeding behavior and whole‐body metabolism via controlling the autonomic output to the visceral organs. Activity of the parasympathetic neurons in the dorsal motor nucleus of the vagus (DMV) determines the vagal tone and thereby modulates the function of the subdiaphragmatic organs. Leptin is highly involved in the regulation of food intake and alters neuronal excitability of brainstem neurons. Transient receptor potential vanilloid type 1 (TRPV1) has also been shown to increase neurotransmission in the brainstem and we tested the hypothesis that TRPV1 regulates presynaptic neurotransmitter release to leptin receptor‐expressing (LepRbEGFP) DMV neurons. Whole‐cell patch‐clamp recordings were performed to determine the effect of TRPV1 activation on excitatory and inhibitory postsynaptic currents (EPSC, IPSC) of LepRbEGFP neurons in the DMV. Capsaicin, a TRPV1 agonist increased the frequency of miniature EPSCs in 50% of LepRbEGFP neurons without altering the frequency of miniature IPSCs in the DMV. Stomach‐projecting LepRbEGFP neurons were identified in the DMV using the transsynaptic retrograde viral tracer PRV‐614. Activation of TRPV1 increased the frequency of mEPSC in ~50% of stomach‐related LepRbEGFP DMV neurons. These data demonstrate that TRPV1 increases excitatory neurotransmission to a subpopulation of LepRbEGFP DMV neurons via presynaptic mechanisms and suggest a potential interaction between TRPV1 and leptin signaling in the DMV. e12160 Our data demonstrate that TRPV1 is involved in the regulation of a subpopulation of leptin receptor‐expressing neurons in the dorsal motor nucleus of the vagus via presynaptic mechanisms.
Collapse
Affiliation(s)
- Andrea Zsombok
- Department of Physiology, School of Medicine, Tulane University, New Orleans, Louisiana Neuroscience Program, School of Science and Engineering, Tulane University, New Orleans, Louisiana
| | - Yanyan Jiang
- Department of Physiology, School of Medicine, Tulane University, New Orleans, Louisiana Neuroscience Program, School of Science and Engineering, Tulane University, New Orleans, Louisiana
| | - Hong Gao
- Department of Physiology, School of Medicine, Tulane University, New Orleans, Louisiana
| | - Imran J Anwar
- Department of Physiology, School of Medicine, Tulane University, New Orleans, Louisiana
| | - Kavon Rezai-Zadeh
- Central Leptin Signaling, Pennington Biomedical Research Center, LSU System, Baton Rouge, Louisiana
| | - Courtney L Enix
- Department of Physiology, School of Medicine, Tulane University, New Orleans, Louisiana
| | - Heike Münzberg
- Central Leptin Signaling, Pennington Biomedical Research Center, LSU System, Baton Rouge, Louisiana
| | - Andrei V Derbenev
- Department of Physiology, School of Medicine, Tulane University, New Orleans, Louisiana Neuroscience Program, School of Science and Engineering, Tulane University, New Orleans, Louisiana
| |
Collapse
|
25
|
Blake CB, Smith BN. cAMP-dependent insulin modulation of synaptic inhibition in neurons of the dorsal motor nucleus of the vagus is altered in diabetic mice. Am J Physiol Regul Integr Comp Physiol 2014; 307:R711-20. [PMID: 24990858 DOI: 10.1152/ajpregu.00138.2014] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
Pathologies in which insulin is dysregulated, including diabetes, can disrupt central vagal circuitry, leading to gastrointestinal and other autonomic dysfunction. Insulin affects whole body metabolism through central mechanisms and is transported into the brain stem dorsal motor nucleus of the vagus (DMV) and nucleus tractus solitarius (NTS), which mediate parasympathetic visceral regulation. The NTS receives viscerosensory vagal input and projects heavily to the DMV, which supplies parasympathetic vagal motor output. Normally, insulin inhibits synaptic excitation of DMV neurons, with no effect on synaptic inhibition. Modulation of synaptic inhibition in DMV, however, is often sensitive to cAMP-dependent mechanisms. We hypothesized that an effect of insulin on GABAergic synaptic transmission may be uncovered by elevating resting cAMP levels in GABAergic terminals. We used whole cell patch-clamp recordings in brain stem slices from control and diabetic mice to identify insulin effects on inhibitory neurotransmission in the DMV in the presence of forskolin to elevate cAMP levels. In the presence of forskolin, insulin decreased the frequency of inhibitory postsynaptic currents (IPSCs) and the paired-pulse ratio of evoked IPSCs in DMV neurons from control mice. This effect was blocked by brefeldin-A, a Golgi-disrupting agent, or indinavir, a GLUT4 blocker, indicating that protein trafficking and glucose transport were involved. In streptozotocin-treated, diabetic mice, insulin did not affect IPSCs in DMV neurons in the presence of forskolin. Results suggest an impairment of cAMP-induced insulin effects on GABA release in the DMV, which likely involves disrupted protein trafficking in diabetic mice. These findings provide insight into mechanisms underlying vagal dysregulation associated with diabetes.
Collapse
Affiliation(s)
- Camille B Blake
- Department of Physiology, University of Kentucky College of Medicine, Lexington, Kentucky
| | - Bret N Smith
- Department of Physiology, University of Kentucky College of Medicine, Lexington, Kentucky
| |
Collapse
|
26
|
Anwar IJ, Derbenev AV. TRPV1-dependent regulation of synaptic activity in the mouse dorsal motor nucleus of the vagus nerve. Front Neurosci 2013; 7:238. [PMID: 24379754 PMCID: PMC3862039 DOI: 10.3389/fnins.2013.00238] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2013] [Accepted: 11/26/2013] [Indexed: 11/24/2022] Open
Abstract
The dorsal motor nucleus of the vagus (DMV) is a key integrative point of the parasympathetic neuronal network localized in the dorsal vagal complex. Activity of neurons in the DMV is closely regulated by synaptic inputs, and regulation of excitatory and inhibitory synapsis by transient receptor potential vanilloid type 1 (TRPV1) has been demonstrated. Activation of TRPV1 by heat, protons, endovanilloids, endocannabinoids, and inflammatory mediators is well established. In our study we hypothesized that TRPV1 contributes to the synaptic transmission of DMV neurons at physiological range of temperature without additional stimuli. Using whole-cell patch-clamp recordings we evaluated the effect of a rapid increase of temperature on excitatory and inhibitory neurotransmission and the contribution of TRPV1 to this response. Rapid increase of temperature from 25 to 37°C increased the frequency of miniature excitatory post-synaptic currents (mEPSC) by 351.7%. The frequency of miniature inhibitory post-synaptic currents (mIPSC) also increased by 184.7%. 5′-iodoresiniferatoxin (5′-iRFT), a selective TRPV1 antagonist, prevented the increase of mEPSC and mIPSC frequency. In summary, our data demonstrate that at physiological range of temperature TRPV1 contributes to presynaptic neurotransmission of DMV neurons.
Collapse
Affiliation(s)
- Imran J Anwar
- Neuroscience Program, Tulane University, New Orleans LA, USA
| | - Andrei V Derbenev
- Neuroscience Program, Tulane University, New Orleans LA, USA ; Department of Physiology, Health Sciences Center, Tulane University, New Orleans LA, USA
| |
Collapse
|
27
|
Derbenev AV, Smith BN. Dexamethasone rapidly increases GABA release in the dorsal motor nucleus of the vagus via retrograde messenger-mediated enhancement of TRPV1 activity. PLoS One 2013; 8:e70505. [PMID: 23936221 PMCID: PMC3728308 DOI: 10.1371/journal.pone.0070505] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2013] [Accepted: 06/23/2013] [Indexed: 11/18/2022] Open
Abstract
Glucocorticoids influence vagal parasympathetic output to the viscera via mechanisms that include modulation of neural circuitry in the dorsal vagal complex, a principal autonomic regulatory center. Glucocorticoids can modulate synaptic neurotransmitter release elsewhere in the brain by inducing release of retrograde signalling molecules. We tested the hypothesis that the glucocorticoid agonist dexamethasone (DEX) modulates GABA release in the rat dorsal motor nucleus of the vagus (DMV). Whole-cell patch-clamp recordings revealed that DEX (1-10 µM) rapidly (i.e. within three minutes) increased the frequency of tetrodotoxin-resistant, miniature IPSCs (mIPSCs) in 67% of DMV neurons recorded in acutely prepared slices. Glutamate-mediated mEPSCs were also enhanced by DEX (10 µM), and blockade of ionotropic glutamate receptors reduced the DEX effect on mIPSC frequency. Antagonists of type I or II corticosteroid receptors blocked the effect of DEX on mIPSCs. The effect was mimicked by application of the membrane-impermeant BSA-conjugated DEX, and intracellular blockade of G protein function with GDP βS in the recorded cell prevented the effect of DEX. The enhancement of GABA release was blocked by the TRPV1 antagonists, 5’-iodoresiniferatoxin or capsazepine, but was not altered by the cannabinoid type 1 receptor antagonist AM251. The DEX effect was prevented by blocking fatty acid amide hydrolysis or by inhibiting anandamide transport, implicating involvement of the endocannabinoid system in the response. These findings indicate that DEX induces an enhancement of GABA release in the DMV, which is mediated by activation of TRPV1 receptors on afferent terminals. The effect is likely induced by anandamide or other ‘endovanilloid’, suggesting activation of a local retrograde signal originating from DMV neurons to enhance synaptic inhibition locally in response to glucocorticoids.
Collapse
Affiliation(s)
- Andrei V. Derbenev
- Department of Physiology, University of Kentucky College of Medicine, Lexington, Kentucky, United States of America
- Department of Cell and Molecular Biology, Tulane University, New Orleans, Louisiana, United States of America
- Department of Physiology, Tulane University School of Medicine, New Orleans, Louisiana, United States of America
| | - Bret N. Smith
- Department of Physiology, University of Kentucky College of Medicine, Lexington, Kentucky, United States of America
- Department of Cell and Molecular Biology, Tulane University, New Orleans, Louisiana, United States of America
- * E-mail:
| |
Collapse
|
28
|
Boychuk CR, Zsombok A, Tasker JG, Smith BN. Rapid Glucocorticoid-Induced Activation of TRP and CB1 Receptors Causes Biphasic Modulation of Glutamate Release in Gastric-Related Hypothalamic Preautonomic Neurons. Front Neurosci 2013; 7:3. [PMID: 23386808 PMCID: PMC3560102 DOI: 10.3389/fnins.2013.00003] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2012] [Accepted: 01/07/2013] [Indexed: 02/02/2023] Open
Abstract
Glucocorticoids rapidly regulate synaptic input to neuroendocrine cells in the hypothalamic paraventricular nucleus (PVN) by inducing the retrograde release of endogenous messengers. Here we investigated the rapid effects of dexamethasone (DEX) on excitatory synaptic input to feeding-related, preautonomic PVN neurons using whole-cell patch-clamp recordings. In ∼50% of identified gastric-related preautonomic PVN neurons, DEX elicited a biphasic synaptic response characterized by an initial rapid and transient increase in the frequency of miniature excitatory postsynaptic currents (mEPSCs), followed by a decrease in mEPSC frequency within 9 min; remaining cells displayed only a decrease in mEPSC frequency. The late-phase decrease in mEPSC frequency was mimicked by the cannabinoid receptor agonists anandamide (AEA) and WIN 55,212-2, and it was blocked by the CB1 receptor antagonist AM251. The biphasic DEX effect was mimicked by AEA. The early increase in mEPSCs was mimicked by activation of transient receptor potential vanilloid type 1 (TRPV1) receptors with capsaicin and by activation of TRPV4 receptors with 4-α-PDD. The increase was reduced, but not blocked, by selective TRPV1 antagonists and in TRPV1 knockout mice; it was blocked completely by the broad-spectrum TRPV antagonist ruthenium red and by combined application of selective TRPV1 and TRPV4 antagonists. The DEX effects were prevented entirely by intracellular infusion of the G-protein inhibitor, GDPβS. Thus, DEX biphasically modulates synaptic glutamate onto a subset of gastric-related PVN neurons, which is likely mediated by induction of a retrograde messenger. The effect includes a TRPV1/4 receptor-mediated transient increase and subsequent CB1 receptor-mediated suppression of glutamate release. Multiphasic modulation of glutamate input to PVN neurons represents a previously unappreciated complexity of control of autonomic output by glucocorticoids and endogenous cannabinoids.
Collapse
Affiliation(s)
- Carie R Boychuk
- Department of Physiology, University of Kentucky College of Medicine Lexington, KY, USA
| | | | | | | |
Collapse
|
29
|
Browning KN, Babic T, Holmes GM, Swartz E, Travagli RA. A critical re-evaluation of the specificity of action of perivagal capsaicin. J Physiol 2013; 591:1563-80. [PMID: 23297311 DOI: 10.1113/jphysiol.2012.246827] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
Perivagal application of capsaicin (1% solution) is considered to cause a selective degeneration of vagal afferent C fibres and has been used extensively to examine the site of action of many gastrointestinal (GI) neuropeptides. The actions of both capsaicin and GI neuropeptides may not be restricted to vagal afferent fibres, however, as other non-sensory neurones have displayed sensitivity to capsaicin and brainstem microinjections of these neuropeptides induce GI effects similar to those obtained upon systemic application. The aim of the present study was to test the hypothesis that perivagal capsaicin induces degeneration of vagal efferents controlling GI functions. Experiments were conducted 7-14 days after 30 min unilateral perivagal application of 0.1-1% capsaicin. Immunohistochemical analyses demonstrated that, as following vagotomy, capsaicin induced dendritic degeneration, decreased choline acetyltransferase but increased nitric oxide synthase immunoreactivity in rat dorsal motor nucleus of the vagus (DMV) neurones. Electrophysiological recordings showed a decreased DMV input resistance and excitability due, in part, to the expression of a large conductance calcium-dependent potassium current and the opening of a transient outward potassium window current at resting potential. Furthermore, the number of DMV neurones excited by thyrotrophin-releasing hormone and the gastric motility response to DMV microinjections of TRH were decreased significantly. Our data indicate that perivagal application of capsaicin induced DMV neuronal degeneration and decreased vagal motor responses. Treatment with perivagal capsaicin cannot therefore be considered selective for vagal afferent C fibres and, consequently, care is needed when using perivagal capsaicin to assess the mechanism of action of GI neuropeptides.
Collapse
Affiliation(s)
- K N Browning
- Department of Neural and Behavioral Sciences, Penn State College of Medicine, 500 University Drive, MC H109, Hershey, PA 17033, USA
| | | | | | | | | |
Collapse
|
30
|
Blake CB, Smith BN. Insulin reduces excitation in gastric-related neurons of the dorsal motor nucleus of the vagus. Am J Physiol Regul Integr Comp Physiol 2012; 303:R807-14. [PMID: 22914748 DOI: 10.1152/ajpregu.00276.2012] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The dorsal motor nucleus of the vagus (DMV) in the caudal brain stem is composed mainly of preganglionic parasympathetic neurons that control the subdiaphragmatic viscera and thus participates in energy homeostasis regulation. Metabolic pathologies, including diabetes, can disrupt vagal circuitry and lead to gastric dysfunction. Insulin receptors (IRs) are expressed in the DMV, and insulin crosses the blood-brain barrier and is transported into the brain stem. Despite growing evidence that insulin action in the brain is critical for energy homeostasis, little is known about insulin's action in the DMV. We used whole cell patch-clamp recordings in brain stem slices to identify effects of insulin on membrane and synaptic input properties of DMV neurons, including a subset of gastric-related cells identified subsequent to injection of a retrograde label into the gastric wall. Insulin application significantly reduced the frequency of spontaneous and miniature excitatory, but not inhibitory postsynaptic currents, with no change in amplitude (P < 0.05). Insulin also directly hyperpolarized the membrane potential (-4.2 ± 1.3 mV; P < 0.05) and reduced action potential firing (P < 0.05). Insulin effects were eliminated in the presence of a ATP-dependent K+ (K(ATP)) channel antagonist tolbutamide (200 μM), or the phosphatidylinositol 3-kinase (PI3K) inhibitor wortmannin (100 nM), suggesting that insulin inhibition of excitatory input to gastric-related DMV neurons was mediated by K(ATP) channels and depended on PI3K activity. Insulin regulation of synaptic input in the DMV may influence autonomic visceral regulation and thus systemic glucose metabolism.
Collapse
Affiliation(s)
- Camille B Blake
- Dept. of Physiology, Univ. of Kentucky College of Medicine, MS508 Chandler Medical Center, 800 Rose St., Lexington, KY 40536, USA
| | | |
Collapse
|
31
|
Issa AT, Miyata K, Heng V, Mitchell KD, Derbenev AV. Increased neuronal activity in the OVLT of Cyp1a1-Ren2 transgenic rats with inducible Ang II-dependent malignant hypertension. Neurosci Lett 2012; 519:26-30. [PMID: 22579820 DOI: 10.1016/j.neulet.2012.05.006] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2012] [Revised: 04/27/2012] [Accepted: 05/02/2012] [Indexed: 11/27/2022]
Abstract
The contribution of angiotensin II (Ang II) to the pathophysiology of hypertension is established based on facts that high levels of circulating Ang II increase vasoconstriction of peripheral arteries causing a rise in blood pressure (BP). In addition, circulating Ang II has various effects on the central nervous system, including the osmosensitive neurons in the organum vasculosum of the lamina terminalis (OVLT). Osmosensitive neurons in the OVLT transduce hypertonicity via the activation of the nonselective cation channel known as transient receptor potential vanilloid 1 (TRPV1), causing membrane depolarization, followed by increased action potential discharge. This effect is absent in mice lacking expression of the TRPV1 gene. Most observations related to the importance of the OVLT in cardiovascular control are mainly based on models of lesion of the entire preoptic periventricular tissue. However, it remains unclear whether neuronal activity and TRPV1 protein expression levels alter in the OVLT of Cyp1a1-Ren2 transgenic rats with inducible Ang II-dependent malignant hypertension. C-fos was used as a marker of neuronal activity. Immunostaining was used to demonstrate distribution of c-fos positive neurons in the OVLT of Cyp1a1Ren2 transgenic rats. Western blot analysis showed increased c-fos and TRPV1 total protein expression levels in the OVLT of hypertensive rats. The present findings demonstrate increased c-fos and TRPV1 expression levels in the OVLT of Cyp1a1-Ren2 transgenic rats with Ang II-dependent malignant hypertension.
Collapse
Affiliation(s)
- Alexandra T Issa
- Department of Physiology, Tulane University, New Orleans, LA, United States
| | | | | | | | | |
Collapse
|
32
|
Bach EC, Smith BN. Presynaptic NMDA receptor-mediated modulation of excitatory neurotransmission in the mouse dorsal motor nucleus of the vagus. J Neurophysiol 2012; 108:1484-91. [PMID: 22696534 DOI: 10.1152/jn.01036.2011] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Activity of neurons in the dorsal motor nucleus of the vagus nerve (DMV) is closely regulated by synaptic input, and regulation of that input by glutamate receptors on presynaptic terminals has been proposed. Presynaptic N-methyl-d-aspartic acid (NMDA) receptors have been identified in a number of brain regions and act to modulate neurotransmitter release, but functional presynaptic NMDA receptors have not been adequately studied in the DMV. This study identified the presence and physiological function of presynaptic NMDA receptors on synaptic input to DMV neurons. Whole-cell patch-clamp recordings from DMV neurons in acute slices from mice revealed prevalent miniature excitatory postsynaptic currents, which were significantly increased in frequency, but not amplitude, by application of NMDA. Antagonism of NMDA receptors with dl-2-amino-5-phosphonopentanoic acid (100 μM) resulted in a decrease in miniature excitatory postsynaptic current frequency and an increase in the paired pulse ratio of responses following afferent stimulation. No consistent effects of presynaptic NMDA receptor modulation were observed on GABAergic inputs. These results suggest that presynaptic NMDA receptors are present in the dorsal vagal complex and function to facilitate the release of glutamate, preferentially onto DMV neurons tonically, with little effect on GABA release. This type of presynaptic modulation represents a potentially novel form of glutamate regulation in the DMV, which may function to regulate glutamate-induced activity of central parasympathetic circuits.
Collapse
Affiliation(s)
- Eva C Bach
- Department of Physiology, University of Kentucky College of Medicine, Lexington, KY 40536, USA
| | | |
Collapse
|
33
|
Gao H, Miyata K, Bhaskaran MD, Derbenev AV, Zsombok A. Transient receptor potential vanilloid type 1-dependent regulation of liver-related neurons in the paraventricular nucleus of the hypothalamus diminished in the type 1 diabetic mouse. Diabetes 2012; 61:1381-90. [PMID: 22492526 PMCID: PMC3357291 DOI: 10.2337/db11-0820] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
The paraventricular nucleus (PVN) of the hypothalamus controls the autonomic neural output to the liver, thereby participating in the regulation of hepatic glucose production (HGP); nevertheless, mechanisms controlling the activity of liver-related PVN neurons are not known. Transient receptor potential vanilloid type 1 (TRPV1) is involved in glucose homeostasis and colocalizes with liver-related PVN neurons; however, the functional role of TRPV1 regarding liver-related PVN neurons has to be elucidated. A retrograde viral tracer was used to identify liver-related neurons within the brain-liver circuit in control, type 1 diabetic, and insulin-treated mice. Our data indicate that TRPV1 regulates liver-related PVN neurons. This TRPV1-dependent excitation diminished in type 1 diabetic mice. In vivo and in vitro insulin restored TRPV1 activity in a phosphatidylinositol 3-kinase/protein kinase C-dependent manner and stimulated TRPV1 receptor trafficking to the plasma membrane. There was no difference in total TRPV1 protein expression; however, increased phosphorylation of TRPV1 receptors was observed in type 1 diabetic mice. Our data demonstrate that TRPV1 plays a pivotal role in the regulation of liver-related PVN neurons. Moreover, TRPV1-dependent excitation of liver-related PVN neurons diminishes in type 1 diabetes, thus indicating that the brain-liver autonomic circuitry is altered in type 1 diabetes and may contribute to the autonomic dysfunction of HGP.
Collapse
Affiliation(s)
- Hong Gao
- Department of Physiology, Tulane University, School of Medicine, New Orleans, Louisiana, USA.
| | | | | | | | | |
Collapse
|
34
|
Abstract
Studies in rodents show that transient receptor potential vanilloid 1 (TRPV1) channels regulate glutamate release at central and peripheral synapses. In humans, a number of nonsynonymous single-nucleotide polymorphisms (SNPs) have been described in the TRPV1 gene, and some of them significantly alter the functionality of the channel. To address the possible role of TRPV1 channels in the regulation of synaptic transmission in humans, we studied how TRPV1 genetic polymorphisms affect cortical excitability measured with transcranial magnetic stimulation (TMS). Two SNPs of the TRPV1 gene were selected and genotyped (rs222747 and rs222749) in a sample of 77 healthy subjects. In previous cell expression studies, the "G" allele of rs222747 was found to enhance the activity of the channel, whereas rs222749 had no functional effect. Allelic variants in the rs222749 region were not associated with altered cortical response to single, paired, and repetitive TMS. In contrast, subjects homozygous for the G allele in rs222747 exhibited larger short-interval intracortical facilitation (a measure of glutamate transmission) explored through paired-pulse TMS of the primary motor cortex. Recruitment curves, short-interval intracortical inhibition, intracortical facilitation, and long-interval intracortical inhibition were unchanged. LTP- and LTD-like plasticity explored through intermittent or continuous theta-burst stimulation was also similar in the "G" and "non-G" subjects. To our knowledge, our results provide the first evidence that TRPV1 channels regulate cortical excitability to paired-pulse stimulation in humans.
Collapse
|
35
|
Functional plasticity of central TRPV1 receptors in brainstem dorsal vagal complex circuits of streptozotocin-treated hyperglycemic mice. J Neurosci 2011; 31:14024-31. [PMID: 21957263 DOI: 10.1523/jneurosci.2081-11.2011] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023] Open
Abstract
Emerging data indicate that central neurons participate in diabetic processes by modulating autonomic output from neurons in the dorsal motor nucleus of the vagus (DMV). We tested the hypothesis that synaptic modulation by transient receptor potential vanilloid type 1 (TRPV1) receptors is reduced in the DMV in slices from a murine model of type 1 diabetes. The TRPV1 agonist capsaicin robustly enhanced glutamate release onto DMV neurons by acting at preterminal receptors in slices from intact mice, but failed to do so in slices from diabetic mice. TRPV1 receptor protein expression in the vagal complex was unaltered. Brief insulin preapplication restored TRPV1-dependent modulation of glutamate release in a PKC- and PI3K-dependent manner. The restorative effect of insulin was prevented by brefeldin A, suggesting that insulin induced TRPV1 receptor trafficking to the terminal membrane. Central vagal circuits critical to the autonomic regulation of metabolism undergo insulin-dependent synaptic plasticity involving TRPV1 receptor modulation in diabetic mice after several days of chronic hyperglycemia.
Collapse
|
36
|
Kawahara H, Drew GM, Christie MJ, Vaughan CW. Inhibition of fatty acid amide hydrolase unmasks CB1 receptor and TRPV1 channel-mediated modulation of glutamatergic synaptic transmission in midbrain periaqueductal grey. Br J Pharmacol 2011; 163:1214-22. [PMID: 21175570 DOI: 10.1111/j.1476-5381.2010.01157.x] [Citation(s) in RCA: 58] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
BACKGROUND AND PURPOSE While arachidonyl ethanolamine (anandamide) produces pharmacological effects mediated by cannabinoid CB1 receptors, it is also an agonist at the transient receptor potential vanilloid type 1 (TRPV1) ion channel. This study examined the cellular actions of anandamide in the midbrain periaqueductal grey (PAG), a region implicated in the analgesic actions of cannabinoids, and which expresses both CB1 receptors and TRPV1. EXPERIMENTAL APPROACH In vitro whole cell patch clamp recordings of glutamatergic excitatory postsynaptic currents (EPSCs) were made from rat and mouse PAG slices. KEY RESULTS Capsaicin (1 µM) increased the rate, but not the amplitude of miniature EPSCs in subpopulations of neurons throughout the rat and mouse PAG. Capsaicin had no effect on miniature EPSCs in PAG neurons from TRPV1 knock-out mice. In mouse PAG neurons, anandamide (30 µM) had no effect on the rate of miniature EPSCs alone, or in the presence of either the CB1 antagonist AM251 (3 µM) or the TRPV1 antagonist iodoresiniferatoxin (300 nM). Anandamide produced a decrease in miniature EPSC rate in the presence of the fatty acid amide hydrolase (FAAH) inhibitor URB597 (1 µM). By contrast, anandamide produced an increase in miniature EPSC rate in the presence of both URB597 and AM251, which was absent in TRPV1 knock-out mice. CONCLUSIONS AND IMPLICATIONS These results suggest that the actions of anandamide within PAG are limited by enzymatic degradation by FAAH. FAAH blockade unmasks both presynaptic inhibition and excitation of glutamatergic synaptic transmission which are mediated via CB1 receptors and TRPV1 respectively.
Collapse
Affiliation(s)
- H Kawahara
- Pain Management Research Institute, Kolling Institute of Medical Research, Northern Clinical School, University of Sydney at Royal North Shore Hospital, St Leonards, NSW, Australia.
| | | | | | | |
Collapse
|
37
|
Liao HT, Lee HJ, Ho YC, Chiou LC. Capsaicin in the periaqueductal gray induces analgesia via metabotropic glutamate receptor-mediated endocannabinoid retrograde disinhibition. Br J Pharmacol 2011; 163:330-45. [PMID: 21232043 DOI: 10.1111/j.1476-5381.2011.01214.x] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
BACKGROUND AND PURPOSE Capsaicin, an agonist of transient receptor potential vanilloid 1 (TRPV1) channels, is pro-nociceptive in the periphery but is anti-nociceptive when administered into the ventrolateral periaqueductal gray (vlPAG), a midbrain region for initiating descending pain inhibition. Here, we investigated how activation of TRPV1 channels in the vlPAG leads to anti-nociception. EXPERIMENTAL APPROACH We examined synaptic transmission and neuronal activity using whole-cell recordings in vlPAG slices in vitro and hot-plate nociceptive responses in rats after drug microinjection into the vlPAG in vivo. KEY RESULTS Capsaicin (1-10 µM) depressed evoked GABAergic inhibitory postsynaptic currents (eIPSCs) in vlPAG slices presynaptically, while increasing miniature excitatory PSC frequency. Capsaicin-induced eIPSC depression was antagonized by cannabinoid CB₁ and metabotropic glutamate (mGlu₅) receptor antagonists, and prevented by inhibiting diacylglycerol lipase (DAGL), which converts DAG into 2-arachidonoylglycerol (2-AG), an endocannabinoid. Capsaicin induced membrane depolarization in 2/3 neurons recorded but, overall, increased neuronal firings by increasing evoked postsynaptic potentials. Intra-vlPAG capsaicin reduced hot-plate responses in rats, effects blocked by CB₁ and mGlu receptor antagonists. Effects of capsaicin were antagonized by SB 366791, a TRPV1 channel antagonist. CONCLUSIONS AND IMPLICATIONS Capsaicin activated TRPV1s on glutamatergic terminals to release glutamate which activated postsynaptic mGlu₅ receptors, yielding 2-AG from DAG by DAGL hydrolysis. 2-AG induces retrograde inhibition (disinhibition) of GABA release via presynaptic CB₁ receptors. This disinhibition in the vlPAG leads to anti-nociception by activating the descending pain inhibitory pathway. This is a novel TRPV1 channel-mediated anti-nociceptive mechanism in the brain and a new interaction between vanilloid and endocannabinoid systems.
Collapse
Affiliation(s)
- H-T Liao
- Graduate Institute of Pharmacology, College of Medicine, National Taiwan University, Taipei, Taiwan
| | | | | | | |
Collapse
|
38
|
Zsombok A, Gao H, Miyata K, Issa A, Derbenev AV. Immunohistochemical localization of transient receptor potential vanilloid type 1 and insulin receptor substrate 2 and their co-localization with liver-related neurons in the hypothalamus and brainstem. Brain Res 2011; 1398:30-9. [PMID: 21620379 DOI: 10.1016/j.brainres.2011.04.048] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2011] [Revised: 04/29/2011] [Accepted: 04/29/2011] [Indexed: 02/05/2023]
Abstract
The central nervous system plays an important role in the regulation of energy balance and glucose homeostasis mainly via controlling the autonomic output to the visceral organs. The autonomic output is regulated by hormones and nutrients to maintain adequate energy and glucose homeostasis. Insulin action is mediated via insulin receptors (IR) resulting in phosphorylation of insulin receptor substrates (IRS) inducing activation of downstream pathways. Furthermore, insulin enhances transient receptor potential vanilloid type 1 (TRPV1) mediated currents. Activation of the TRPV1 receptor increases excitatory neurotransmitter release in autonomic centers of the brain, thereby impacting energy and glucose homeostasis. The aim of this study is to determine co-expression of IRS2 and TRPV1 receptors in the paraventricular nucleus of the hypothalamus (PVN) and dorsal motor nucleus of the vagus (DMV) in the mouse brain as well as expression of IRS2 and TRPV1 receptors at liver-related preautonomic neurons pre-labeled with a trans-neural, viral tracer (PRV-152). The data indicate that IRS2 and TRPV1 receptors are present and co-express in the PVN and the DMV. A large portion (over 50%) of the liver-related preautonomic DMV and PVN neurons expresses IRS2. Moreover, the majority of liver-related DMV and PVN neurons also express TRPV1 receptors, suggesting that insulin and TRPV1 actions may affect liver-related preautonomic neurons.
Collapse
Affiliation(s)
- Andrea Zsombok
- Department of Physiology, Tulane University Health Science Center, New Orleans, LA 70112, USA.
| | | | | | | | | |
Collapse
|
39
|
Geraghty DP, Mazzone SB, Carter C, Kunde DA. Effects of systemic capsaicin treatment on TRPV1 and Tachykinin NK(1) receptor distribution and function in the nucleus of the solitary tract of the adult rat. Pharmacology 2011; 87:214-23. [PMID: 21430411 DOI: 10.1159/000324530] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2010] [Accepted: 01/20/2011] [Indexed: 01/03/2023]
Abstract
Vanilloids including capsaicin and resiniferatoxin (RTX) have been identified as potential novel anti-inflammatory and analgesic compounds. We have previously shown that systemic capsaicin administration to neonatal rats evokes profound long-term alterations in transient receptor potential vanilloid 1 (TRPV1)- and neurokinin 1 (NK(1)) receptor-mediated respiratory responses in the commissural nucleus of the solitary tract (cNTS). Whether this effect of capsaicin is unique to developmentally immature animals is unknown. Therefore, in the present study, we investigated the effects of systemic capsaicin administration to adult rats on NK(1) receptor binding sites, TRPV1 and NK(1) immunoreactivity and function in the cNTS. Microinjection of capsaicin (1 nmol) or RTX (75 pmol) into the cNTS of vehicle-pretreated rats produced a profound bradypnoea (maximum change: -45 breaths·min(-1)) and a small increase in tidal volume (VT). Similarly, microinjection of the selective NK(1) receptor agonists [Sar(9), Met(O(2))(11)]substance P (SP; 66 pmol) and septide (20 pmol) decreased respiratory frequency and increased VT. Thirteen to 18 days after systemic administration of capsaicin (125 mg·kg(-1) s.c.), the bradypnoeic responses to both capsaicin and RTX were absent (p < 0.05), indicative of sensory neuron ablation/desensitisation. Systemic capsaicin pretreatment significantly (p < 0.05) reduced the density of both [(125)I]Bolton-Hunter SP binding sites (NK(1) receptors) and NK(1) receptor immunoreactivity in the cNTS, but did not alter the respiratory responses evoked by microinjection of [Sar(9), Met(O(2))(11)]SP and septide into this region. These studies show that systemic capsaicin administration reduces NK(1) receptor density in the cNTS without adversely affecting NK(1) receptor function at this site. We speculate that adult rats may be more resistant than neonatal rats to the neuroplastic effects of systemic capsaicin administration.
Collapse
Affiliation(s)
- Dominic P Geraghty
- School of Human Life Sciences, University of Tasmania, Launceston, Tas., Australia.
| | | | | | | |
Collapse
|
40
|
Zschenderlein C, Gebhardt C, von Bohlen und Halbach O, Kulisch C, Albrecht D. Capsaicin-induced changes in LTP in the lateral amygdala are mediated by TRPV1. PLoS One 2011; 6:e16116. [PMID: 21249195 PMCID: PMC3020947 DOI: 10.1371/journal.pone.0016116] [Citation(s) in RCA: 66] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2010] [Accepted: 12/14/2010] [Indexed: 01/15/2023] Open
Abstract
The transient receptor potential vanilloid type 1 (TRPV1) channel is a well recognized polymodal signal detector that is activated by painful stimuli such as capsaicin. Here, we show that TRPV1 is expressed in the lateral nucleus of the amygdala (LA). Despite the fact that the central amygdala displays the highest neuronal density, the highest density of TRPV1 labeled neurons was found within the nuclei of the basolateral complex of the amygdala. Capsaicin specifically changed the magnitude of long-term potentiation (LTP) in the LA in brain slices of mice depending on the anesthetic (ether, isoflurane) used before euthanasia. After ether anesthesia, capsaicin had a suppressive effect on LA-LTP both in patch clamp and in extracellular recordings. The capsaicin-induced reduction of LTP was completely blocked by the nitric oxide synthase (NOS) inhibitor L-NAME and was absent in neuronal NOS as well as in TRPV1 deficient mice. The specific antagonist of cannabinoid receptor type 1 (CB1), AM 251, was also able to reduce the inhibitory effect of capsaicin on LA-LTP, suggesting that stimulation of TRPV1 provokes the generation of anandamide in the brain which seems to inhibit NO synthesis. After isoflurane anesthesia before euthanasia capsaicin caused a TRPV1-mediated increase in the magnitude of LA-LTP. Therefore, our results also indicate that the appropriate choice of the anesthetics used is an important consideration when brain plasticity and the action of endovanilloids will be evaluated. In summary, our results demonstrate that TRPV1 may be involved in the amygdala control of learning mechanisms.
Collapse
Affiliation(s)
- Carsten Zschenderlein
- Institute of Neurophysiology, Charité - Universitätsmedizin Berlin, CVK, Berlin, Germany
| | - Christine Gebhardt
- Institute of Neurophysiology, Charité - Universitätsmedizin Berlin, CVK, Berlin, Germany
| | | | - Christoph Kulisch
- Institute of Neurophysiology, Charité - Universitätsmedizin Berlin, CVK, Berlin, Germany
| | - Doris Albrecht
- Institute of Neurophysiology, Charité - Universitätsmedizin Berlin, CVK, Berlin, Germany
| |
Collapse
|
41
|
Derbenev AV, Duale H, Rabchevsky AG, Smith BN. Electrophysiological characteristics of identified kidney-related neurons in adult rat spinal cord slices. Neurosci Lett 2010; 474:168-172. [PMID: 20303390 DOI: 10.1016/j.neulet.2010.03.036] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2010] [Revised: 03/11/2010] [Accepted: 03/12/2010] [Indexed: 10/19/2022]
Abstract
Whole-cell patch-clamp recordings were made from kidney-related neurons in the intermediolateral cell column (IML) in horizontal slices of thoracolumbar spinal cord from adult rats. Kidney-related neurons were identified in vitro subsequent to inoculation of the kidney with a fluorescent, retrograde, transynaptic pseudorabies viral label (i.e., PRV-152). Kidney-related neurons detected in the IML expressed choline acetyltransferase, characteristic of spinal preganglionic motor neurons. Their mean resting potential was -51+/-4 mV and input resistance was 448+/-39 MOmega. Both spontaneous inhibitory and excitatory post-synaptic currents (i.e., sIPSCs and sEPSCs) were observed in all neurons. The mean frequency for sEPSCs (3.1+/-1 Hz) was approximately 2.5 times that for sIPSCs (1.4+/-0.3 Hz). Application of the glycine and GABA(A) receptor-linked Cl(-) channel blocker, picrotoxin (100 microM) blocked sIPSCs, while the ionotropic glutamate receptor antagonist, kynurenic acid (1 mM) blocked all sEPSCs, indicating they were mediated by GABA/glycine and glutamate receptors, respectively. Thus, using PRV-152 labeling allowed whole-cell patch-clamp recording of neurons in the adult spinal cord, which were kidney-related. Excitatory glutamatergic input dominated synaptic responses in these cells, the membrane characteristics of which resembled those of immature IML neurons. Combined PRV-152 pre-labeling and whole-cell patch-clamp recordings may allow more effective analysis of synaptic plasticity seen in adult models of injury or chronic disease.
Collapse
Affiliation(s)
- Andrei V Derbenev
- Department of Physiology, University of Kentucky, Lexington, KY 40536, United States
| | - Hanad Duale
- Department of Physiology, University of Kentucky, Lexington, KY 40536, United States; Spinal Cord and Brain Injury Research Center, University of Kentucky, Lexington, KY 40536, United States
| | - Alexander G Rabchevsky
- Department of Physiology, University of Kentucky, Lexington, KY 40536, United States; Spinal Cord and Brain Injury Research Center, University of Kentucky, Lexington, KY 40536, United States
| | - Bret N Smith
- Department of Physiology, University of Kentucky, Lexington, KY 40536, United States.
| |
Collapse
|
42
|
Musella A, De Chiara V, Rossi S, Cavasinni F, Castelli M, Cantarella C, Mataluni G, Bernardi G, Centonze D. Transient receptor potential vanilloid 1 channels control acetylcholine/2-arachidonoylglicerol coupling in the striatum. Neuroscience 2010; 167:864-71. [PMID: 20219639 DOI: 10.1016/j.neuroscience.2010.02.058] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2009] [Revised: 02/20/2010] [Accepted: 02/22/2010] [Indexed: 10/19/2022]
Abstract
The neurotransmitter acetylcholine (Ach) controls both excitatory and inhibitory synaptic transmission in the striatum. Here, we investigated the involvement of the endocannabinoid system in Ach-mediated inhibition of striatal GABA transmission, and the potential role of transient receptor potential vanilloid 1 (TRPV1) channels in the control of Ach-endocannabinoid coupling. We found that inhibition of Ach degradation and direct pharmacological stimulation of muscarinic M1 receptors reduced striatal inhibitory postsynaptic currents (IPSCs) through the stimulation of 2-arachidonoylglicerol (2AG) synthesis and the activation of cannabinoid CB1 receptors. The effects of M1 receptor activation on IPSCs were occlusive with those of metabotropic glutamate receptor 5 stimulation, and were prevented in the presence of capsaicin, agonist of TRPV1 channels. Elevation of anandamide (AEA) tone with URB597, a blocker of fatty acid amide hydrolase, mimicked the effects of capsaicin, indicating that endogenous AEA acts as an endovanilloid substance in the control of M1-dependent 2AG-mediated synaptic effects in the striatum. Accordingly, both capsaicin and URB597 effects were absent in mice lacking TRPV1 channels. Pharmacological interventions targeting AEA metabolism and TRPV1 channels might be considered alternative therapeutic routes in disorders of striatal cholinergic or endocannabinoid neurotransmission.
Collapse
Affiliation(s)
- A Musella
- Clinica Neurologica, Dipartimento di Neuroscienze, Università Tor Vergata, Rome, Italy
| | | | | | | | | | | | | | | | | |
Collapse
|
43
|
Bhaskaran MD, Smith BN. Effects of TRPV1 activation on synaptic excitation in the dentate gyrus of a mouse model of temporal lobe epilepsy. Exp Neurol 2010; 223:529-36. [PMID: 20144892 DOI: 10.1016/j.expneurol.2010.01.021] [Citation(s) in RCA: 87] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2009] [Revised: 01/08/2010] [Accepted: 01/31/2010] [Indexed: 11/25/2022]
Abstract
Temporal lobe epilepsy (TLE) is a condition characterized by an imbalance between excitation and inhibition in the temporal lobe. Hallmarks of this change are axon sprouting and accompanying synaptic reorganization in the temporal lobe. Synthetic and endogenous cannabinoids have variable therapeutic potential in treating intractable temporal lobe epilepsy, in part because cannabinoid ligands can bind multiple receptor types. This study utilized in vitro electrophysiological methods to examine the effect of transient receptor potential vanilloid type 1 (TRPV1) activation in dentate gyrus granule cells in a murine model of TLE. Capsaicin, a selective TRPV1 agonist had no measurable effect on overall synaptic input to granule cells in control animals, but significantly enhanced spontaneous and miniature EPSC frequency in mice with TLE. Exogenous application of anandamide, an endogenous cannabinoid that acts at both TRPV1 and cannabinoid type 1 receptors (CB1R), also enhanced glutamate release in the presence of a CB1R antagonist. Anandamide reduced the EPSC frequency when TRPV1 were blocked with capsazepine. Western blot analysis of TRPV1 receptor indicated protein expression was significantly greater in the dentate gyrus of mice with TLE compared with control mice. This study indicates that a prominent cannabinoid agonist can increase excitatory circuit activity in the synaptically reorganized dentate gyrus of mice with TLE by activating TRPV1 receptors, and suggests caution in designing anticonvulsant therapy based on modulating the endocannabinoid system.
Collapse
Affiliation(s)
- Muthu D Bhaskaran
- Department of Cell and Molecular Biology, Tulane University, New Orleans, Louisiana 70118, USA
| | | |
Collapse
|
44
|
Convergence of cranial visceral afferents within the solitary tract nucleus. J Neurosci 2009; 29:12886-95. [PMID: 19828803 DOI: 10.1523/jneurosci.3491-09.2009] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Primary afferent axons within the solitary tract (ST) relay homeostatic information via glutamatergic synapses directly to second-order neurons within the nucleus of the solitary tract (NTS). These primary afferents arise from multiple organ systems and relay multiple sensory modalities. How this compact network organizes the flow of primary afferent information will shape central homeostatic control. To assess afferent convergence and divergence, we recorded ST-evoked synaptic responses in pairs of medial NTS neurons in horizontal brainstem slices. ST shocks activated EPSCs along monosynaptic or polysynaptic pathways. Gradations in shock intensity discriminated multiple inputs and stimulus recruitment profiles indicated that each EPSC was unitary. In 24 pairs, 75% were second-order neurons with 64% receiving one direct ST input with the remainder receiving additional convergent ST afferent inputs (22% two; 14% three monosynaptic ST-EPSCs). Some (34%) second-order neurons received polysynaptic EPSCs. Neurons receiving only higher-order inputs were uncommon (13%). Most ST-EPSCs were completely independent, but 4 EPSCs of a total of 81 had equal thresholds, highly correlated latencies, and synchronized synaptic failures consistent with divergence from a single source ST axon or from a common interneuron producing a pair of polysynaptic EPSCs. We conclude that ST afferent inputs are remarkably independent with little evidence of substantial shared information. Individual cells receive highly focused information from the viscera. Thus, afferent excitation of second-order NTS neurons is generally dominated by single visceral afferents and therefore focused on a single afferent modality and/or organ region.
Collapse
|
45
|
Role of endocannabinoids and endovanilloids in Ca2+ signalling. Cell Calcium 2009; 45:611-24. [DOI: 10.1016/j.ceca.2009.03.003] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2009] [Revised: 03/03/2009] [Accepted: 03/11/2009] [Indexed: 12/14/2022]
|
46
|
Depolarization-induced release of endocannabinoids by murine dorsal motor nucleus of the vagus nerve neurons differentially regulates inhibitory and excitatory neurotransmission. Neuropharmacology 2009; 56:1106-15. [DOI: 10.1016/j.neuropharm.2009.03.009] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2008] [Revised: 02/26/2009] [Accepted: 03/18/2009] [Indexed: 11/17/2022]
|
47
|
Abstract
Hypocretin/orexin, produced by a group of neurons in the lateral hypothalamus/perifornical area, enhances cognitive arousal and also may play a crucial role in modulating the neuroendocrine system. How hypocretin modulates the endocrine system remains an open question. Hypocretin cells innervate the mediobasal hypothalamus where they can potentially influence the activity of specific cell populations within the arcuate nucleus. Here, we examine whether hypocretin modulates the median eminence-projecting proopiomelanocortin (POMC) neurons identified by selective green fluorescent protein expression and antidromic stimulation or retrograde Evans blue dye tracing in transgenic mice. We find that POMC neurons, in general, and, in addition, those that project their axons to the median eminence, were robustly activated by hypocretin in a dose-dependent manner. These excitatory actions included a threefold increase in spike frequency and direct membrane depolarization of up to 22 mV (mean, 17.9+/-7.2 mV). Direct postsynaptic depolarization was decreased at more positive membrane potentials, inhibited by the sodium-calcium exchanger antagonist KB-R7943, and reduced by lowering the bath temperature, or by buffering the postsynaptic calcium with BAPTA, suggesting that the primary mechanism for hypocretin-mediated excitation is the activation of the sodium-calcium exchanger. Hypocretin also enhanced excitatory inputs to POMC cells via a presynaptic mechanism and indirectly increased the release of GABA onto these cells in a spike-dependent manner. However, these synaptic actions were not necessary to cause postsynaptic membrane depolarization and spiking. Thus, in contrast to previous suggestions that hypocretin inhibited POMC cells, our results demonstrate robust direct excitation of POMC neurons by hypocretin.
Collapse
|
48
|
Musella A, De Chiara V, Rossi S, Prosperetti C, Bernardi G, Maccarrone M, Centonze D. TRPV1 channels facilitate glutamate transmission in the striatum. Mol Cell Neurosci 2009; 40:89-97. [DOI: 10.1016/j.mcn.2008.09.001] [Citation(s) in RCA: 107] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2008] [Revised: 08/05/2008] [Accepted: 09/15/2008] [Indexed: 01/27/2023] Open
|
49
|
Plasticity of central autonomic neural circuits in diabetes. Biochim Biophys Acta Mol Basis Dis 2008; 1792:423-31. [PMID: 19110053 DOI: 10.1016/j.bbadis.2008.12.001] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2008] [Revised: 11/26/2008] [Accepted: 12/02/2008] [Indexed: 12/11/2022]
Abstract
Regulation of energy metabolism is controlled by the brain, in which key central neuronal circuits process a variety of information reflecting nutritional state. Special sensory and gastrointestinal afferent neural signals, along with blood-borne metabolic signals, impinge on parallel central autonomic circuits located in the brainstem and hypothalamus to signal changes in metabolic balance. Specifically, neural and humoral signals converge on the brainstem vagal system and similar signals concentrate in the hypothalamus, with significant overlap between both sensory and motor components of each system and extensive cross-talk between the systems. This ultimately results in production of coordinated regulatory autonomic and neuroendocrine cues to maintain energy homeostasis. Therapeutic metabolic adjustments can be accomplished by modulating viscerosensory input or autonomic motor output, including altering parasympathetic circuitry related to GI, pancreas, and liver regulation. These alterations can include pharmacological manipulation, but surgical modification of neural signaling should also be considered. In addition, central control of visceral function is often compromised by diabetes mellitus, indicating that circuit modification should be studied in the context of its effect on neurons in the diabetic state. Diabetes has traditionally been handled as a peripheral metabolic disease, but the central nervous system plays a crucial role in regulating glucose homeostasis. This review focuses on key autonomic brain areas associated with management of energy homeostasis and functional changes in these areas associated with the development of diabetes.
Collapse
|
50
|
Chen J, Paudel KS, Derbenev AV, Smith BN, Stinchcomb AL. Simultaneous Quantification of Anandamide and Other Endocannabinoids in Dorsal Vagal Complex of Rat Brainstem by LC-MS. Chromatographia 2008; 69:1-7. [PMID: 20046895 DOI: 10.1365/s10337-008-0841-x] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
A quantitative method has been developed and validated for the simultaneous determination of anandamide (AEA), docosatetraenylethanolamide (DEA) and N-arachidonyldopamine (NADA) in dorsal vagal complex (DVC) of rat brainstem by liquid chromatographic-electrospray ionization mass spectrometry. The analytes were extracted from the tissue samples of rat brainstem by a single step liquid extraction technique using acetonitrile. The chromatographic separation was conducted on a C18 column using a gradient mobile phase consisting of methanol and water at a flow rate of 0.3 mL min(-1). The analytes were quantified by positive electrospray ionization mass spectrometry with selected ion monitoring (SIM) mode. The limits of detection (LOD) for AEA, DEA and NADA were 0.5, 1 and 0.5 ng mL(-1), respectively. This method required only simple processing of the samples and could be applied to monitor the change in the level of these compounds in DVC of the rat brain tissue. Time dependent (10-70 min) accumulation of the endocannabinoids (AEA, DEA, and NADA) in brain tissue was also studied, which included a novel examination of the accumulation of DEA as a function of time in rat brain tissue after decapitation.
Collapse
Affiliation(s)
- Jing Chen
- Department of Pharmaceutical Sciences, College of Pharmacy, University of Kentucky, Lexington, KY 40536-0082, USA
| | | | | | | | | |
Collapse
|