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Flores RA, Dos-Santos RC, Rodrigues-Santos I, de Jesus AA, Antunes-Rodrigues J, Elias LLK. Tonic noradrenergic input to neurons in the dorsal raphe nucleus mediates food intake in male mice. Behav Brain Res 2024; 462:114872. [PMID: 38266779 DOI: 10.1016/j.bbr.2024.114872] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2023] [Revised: 01/08/2024] [Accepted: 01/18/2024] [Indexed: 01/26/2024]
Abstract
The dorsal raphe nucleus (DRN) is essential for the control of food intake. Efferent projections from the DRN extend to several forebrain regions that are involved in the control of food intake. However, the neurotransmitters released in the DRN related to the control of food intake are not known. We have previously demonstrated that a tonic α1 action on DRN neurons contributes to satiety in the fed rats. In this study we investigated the participation of norepinephrine (NE) signaling in the DRN in the satiety response. Intra-DRN administration of NE causes an increase in the 2-hour food intake of sated mice, an effect that was blocked by previous administration of yohimbine, an α2 antagonist. Similarly, Intra-DRN administration of clonidine, an α2 agonist, increases food intake in sated mice. This result indicates that in the satiated mice exogenous NE acts on α2 receptors to increase food intake. Furthermore, administration of phenylephrine, an α1 agonist, decreases food intake in fasted mice and prazosin, an α1 antagonist, increases food intake in the sated mice. Taken together these results indicate that, in a satiated condition, a tonic α1 adrenergic action on the DRN neurons inhibits food intake and that exogenous NE administered to the DRN acts on α2 adrenergic receptors to increase food intake. These data reinforce the intricate neuronal functioning of the DRN and its effects on feeding.
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Affiliation(s)
- Rafael Appel Flores
- Department of Physiology, Ribeirão Preto Medical School, University of São Paulo, 3900, Bandeirantes Av., Prof. Dr. Zeferino Vaz Building, ZIP Code: 14049-900, Ribeirão Preto, SP, Brazil.
| | - Raoni C Dos-Santos
- Department of Cell and Molecular Biology, Tulane University, 6602 Freret St, New Orleans, Percival Stern Hall, ZIP Code: 70118, New Orleans, Louisiana, USA.
| | - Isabelle Rodrigues-Santos
- Department of Physiology, Ribeirão Preto Medical School, University of São Paulo, 3900, Bandeirantes Av., Prof. Dr. Zeferino Vaz Building, ZIP Code: 14049-900, Ribeirão Preto, SP, Brazil
| | - Aline Alves de Jesus
- Department of Physiology, Ribeirão Preto Medical School, University of São Paulo, 3900, Bandeirantes Av., Prof. Dr. Zeferino Vaz Building, ZIP Code: 14049-900, Ribeirão Preto, SP, Brazil
| | - José Antunes-Rodrigues
- Department of Physiology, Ribeirão Preto Medical School, University of São Paulo, 3900, Bandeirantes Av., Prof. Dr. Zeferino Vaz Building, ZIP Code: 14049-900, Ribeirão Preto, SP, Brazil
| | - Lucila L K Elias
- Department of Physiology, Ribeirão Preto Medical School, University of São Paulo, 3900, Bandeirantes Av., Prof. Dr. Zeferino Vaz Building, ZIP Code: 14049-900, Ribeirão Preto, SP, Brazil.
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Aklan I, Sayar-Atasoy N, Deng F, Kim H, Yavuz Y, Rysted J, Laule C, Davis D, Li Y, Atasoy D. Dorsal raphe serotonergic neurons suppress feeding through redundant forebrain circuits. Mol Metab 2023; 69:101676. [PMID: 36682413 PMCID: PMC9923194 DOI: 10.1016/j.molmet.2023.101676] [Citation(s) in RCA: 9] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/16/2022] [Revised: 12/04/2022] [Accepted: 01/13/2023] [Indexed: 01/21/2023] Open
Abstract
OBJECTIVE Serotonin (5HT) is a well-known anorexigenic molecule, and 5HT neurons of dorsal raphe nucleus (DRN) have been implicated in suppression of feeding; however, the downstream circuitry is poorly understood. Here we explored major projections of DRN5HT neurons for their capacity to modulate feeding. METHODS We used optogenetics to selectively activate DRN5HT axonal projections in hypothalamic and extrahypothalamic areas and monitored food intake. We next used fiber photometry to image the activity dynamics of DRN5HT axons and 5HT levels in projection areas in response feeding and metabolic hormones. Finally, we used electrophysiology to determine how DRN5HT axons affect downstream neuron activity. RESULTS We found that selective activation of DRN5HT axons in (DRN5HT → LH) and (DRN5HT → BNST) suppresses feeding whereas activating medial hypothalamic projections has no effect. Using in vivo imaging, we found that food access and satiety hormones activate DRN5HT projections to LH where they also rapidly increase extracellular 5HT levels. Optogenetic mapping revealed that DRN5HT → LHvGAT and DRN5HT → LHvGlut2 connections are primarily inhibitory and excitatory respectively. Further, in addition to its direct action on LH neurons, we found that 5HT suppresses GABA release from presynaptic terminals arriving from AgRP neurons. CONCLUSIONS These findings define functionally redundant forebrain circuits through which DRN5HT neurons suppress feeding and reveal that these projections can be modulated by metabolic hormones.
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Affiliation(s)
- Iltan Aklan
- Department of Neuroscience and Pharmacology, Roy J. and Lucille A. Carver College of Medicine, University of Iowa, Iowa City, IA, USA
| | - Nilufer Sayar-Atasoy
- Department of Neuroscience and Pharmacology, Roy J. and Lucille A. Carver College of Medicine, University of Iowa, Iowa City, IA, USA
| | - Fei Deng
- State Key Laboratory of Membrane Biology, Peking University School of Life Sciences, Beijing 100871, China
| | - Hyojin Kim
- Department of Neuroscience and Pharmacology, Roy J. and Lucille A. Carver College of Medicine, University of Iowa, Iowa City, IA, USA
| | - Yavuz Yavuz
- Department of Neuroscience and Pharmacology, Roy J. and Lucille A. Carver College of Medicine, University of Iowa, Iowa City, IA, USA,Department of Physiology, School of Medicine, Yeditepe University, Istanbul, Turkey
| | - Jacob Rysted
- Department of Neuroscience and Pharmacology, Roy J. and Lucille A. Carver College of Medicine, University of Iowa, Iowa City, IA, USA
| | - Connor Laule
- Department of Neuroscience and Pharmacology, Roy J. and Lucille A. Carver College of Medicine, University of Iowa, Iowa City, IA, USA
| | - Debbie Davis
- Department of Neuroscience and Pharmacology, Roy J. and Lucille A. Carver College of Medicine, University of Iowa, Iowa City, IA, USA
| | - Yulong Li
- State Key Laboratory of Membrane Biology, Peking University School of Life Sciences, Beijing 100871, China
| | - Deniz Atasoy
- Department of Neuroscience and Pharmacology, Roy J. and Lucille A. Carver College of Medicine, University of Iowa, Iowa City, IA, USA; Iowa Neuroscience Institute, Roy J. and Lucille A. Carver College of Medicine, University of Iowa, Iowa City, IA, USA; Fraternal Order of Eagles Diabetes Research Center (FOEDRC), Roy J. and Lucille A. Carver College of Medicine, University of Iowa, Iowa City, IA, USA.
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Flores RA, Dos-Santos RC, Steinbach R, Rodrigues-Santos I, de Jesus AA, Antunes-Rodrigues J, Paschoalini MA. α-1 Adrenoceptor Activation in the Dorsal Raphe Nucleus Decreases Food Intake in Fasted Rats. Front Physiol 2021; 12:775070. [PMID: 34899395 PMCID: PMC8656260 DOI: 10.3389/fphys.2021.775070] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2021] [Accepted: 10/21/2021] [Indexed: 01/12/2023] Open
Abstract
The dorsal raphe (DR) nucleus is involved in a myriad of physiological functions, such as the control of sleep-wake cycle, motivation, pain, energy balance, and food intake. We have previously demonstrated that in ad libitum fed rats the intra-DR administration of phenylephrine, an α-1 receptor agonist, does not affect food intake, whereas clonidine, an α-2 receptor agonist, potently stimulates food intake. These results indicated that in fed rats an increased adrenergic tonus blocked food intake, since the activation of α-2 auto-receptors, which decreases pre-synaptic release of adrenaline/noradrenaline, affected food intake. Thus, in this study we assessed whether the response to adrenergic stimuli would differ after overnight fasting, a situation of low adrenergic activity in the DR. Intra-DR administration of adrenaline and noradrenaline blocked food intake evoked by overnight fasting. Similarly, phenylephrine administration decreased hunger-induced food intake. These changes in food intake were accompanied by changes in other behaviors, such as increased immobility time and feeding duration. On the other hand, intra-DR administration of clonidine did not affect food-intake or associated behaviors. These results further support the hypothesis that in fed animals, increased adrenergic tonus in DR neurons inhibiting feeding, while in fasted rats the adrenergic tonus decreases and favors food intake. These data indicate a possible mechanism through which adrenergic input to the DRN contributes to neurobiology of feeding.
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Affiliation(s)
- Rafael Appel Flores
- Department of Physiology, Ribeirão Preto School of Medicine, São Paulo University, Ribeirão Preto, Brazil.,Department of Physiological Sciences, Center of Biological Sciences, Federal University of Santa Catarina, Florianópolis, Brazil
| | - Raoni Conceição Dos-Santos
- Department of Physiology, Ribeirão Preto School of Medicine, São Paulo University, Ribeirão Preto, Brazil
| | - Renata Steinbach
- Department of Physiological Sciences, Center of Biological Sciences, Federal University of Santa Catarina, Florianópolis, Brazil
| | - Isabelle Rodrigues-Santos
- Department of Physiology, Ribeirão Preto School of Medicine, São Paulo University, Ribeirão Preto, Brazil
| | - Aline Alves de Jesus
- Department of Physiology, Ribeirão Preto School of Medicine, São Paulo University, Ribeirão Preto, Brazil
| | - José Antunes-Rodrigues
- Department of Physiology, Ribeirão Preto School of Medicine, São Paulo University, Ribeirão Preto, Brazil
| | - Marta Aparecida Paschoalini
- Department of Physiological Sciences, Center of Biological Sciences, Federal University of Santa Catarina, Florianópolis, Brazil
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Kang SW. Central Nervous System Associated With Light Perception and Physiological Responses of Birds. Front Physiol 2021; 12:723454. [PMID: 34744764 PMCID: PMC8566752 DOI: 10.3389/fphys.2021.723454] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2021] [Accepted: 09/20/2021] [Indexed: 11/13/2022] Open
Abstract
Environmental light that animal receives (i.e., photoperiod and light intensity) has recently been shown that it affects avian central nervous system for the physiological responses to the environment by up or downregulation of dopamine and serotonin activities, and this, in turn, affects the reproductive function and stress-related behavior of birds. In this study, the author speculated on the intriguing possibility that one of the proposed avian deep-brain photoreceptors (DBPs), i.e., melanopsin (Opn4), may play roles in the dual sensory-neurosecretory cells in the hypothalamus, midbrain, and brain stem for the behavior and physiological responses of birds by light. Specifically, the author has shown that the direct light perception of premammillary nucleus dopamine-melatonin (PMM DA-Mel) neurons is associated with the reproductive activation in birds. Although further research is required to establish the functional role of Opn4 in the ventral tegmental area (VTA), dorsal raphe nucleus, and caudal raphe nucleus in the light perception and physiological responses of birds, it is an exciting prospect because the previous results in birds support this hypothesis that Opn4 in the midbrain DA and serotonin neurons may play significant roles on the light-induced welfare of birds.
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Affiliation(s)
- Seong W. Kang
- Department of Poultry Science, Center of Excellence for Poultry Science, University of Arkansas, Fayetteville, AR, United States
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Ye Q, Zhang X. Serotonin activates paraventricular thalamic neurons through direct depolarization and indirect disinhibition from zona incerta. J Physiol 2021; 599:4883-4900. [PMID: 34510418 DOI: 10.1113/jp282088] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2021] [Accepted: 09/10/2021] [Indexed: 12/11/2022] Open
Abstract
Paraventricular thalamus (PVT) is a midline thalamic area that receives dense GABA projections from zona incerta (ZI) for the regulation of feeding behaviours. Activation of central serotonin (5-HT) signalling is known to inhibit food intake. Although previous studies have reported both 5-HT fibres and receptors in the PVT, it remains unknown how 5-HT regulates PVT neurons and whether PVT 5-HT signalling is involved in the control of food intake. Using slice patch-clamp recordings in combination with optogenetics, we found that 5-HT not only directly excited PVT neurons by activating 5-HT7 receptors to modulate hyperpolarization-activated cyclic nucleotide-gated (HCN) channels but also disinhibited these neurons by acting on presynaptic 5-HT1A receptors to reduce GABA inhibition. Specifically, 5-HT depressed photostimulation-evoked inhibitory postsynaptic currents (eIPSCs) in PVT neurons innervated by channelrhodopsin-2-positive GABA axons from ZI. Using paired-pulse photostimulation, we found 5-HT increased paired-pulse ratios of eIPSCs, suggesting 5-HT decreases ZI-PVT GABA release. Furthermore, we found that exposure to a high-fat-high-sucrose diet for 2 weeks impaired both 5-HT inhibition of ZI-PVT GABA transmission and 5-HT excitation of PVT neurons. Using retrograde tracer in combination with immunocytochemistry and slice electrophysiology, we found that PVT-projecting dorsal raphe neurons expressed 5-HT and were inhibited by food deprivation. Together, our study reveals the mechanism by which 5-HT activates PVT neurons through both direct excitation and indirect disinhibition from the ZI. The downregulation in 5-HT excitation and disinhibition of PVT neurons may contribute to the development of overeating and obesity after chronic high-fat diet. KEY POINTS: Serotonin (5-HT) depolarizes and excites paraventricular thalamus (PVT) neurons. 5-HT7 receptors are responsible for 5-HT excitation of PVT neurons and the coupling of hyperpolarization-activated cyclic nucleotide-gated (HCN) channels to 5-HT receptors in part mediates the excitatory effect of 5-HT. 5-HT depresses the frequency of spontaneous inhibitory but not excitatory postsynaptic currents in PVT neurons. 5-HT1A receptors contribute to the depressive effect of 5-HT on inhibitory transmissions. 5-HT inhibits GABA release from zona incerta (ZI) GABA terminals in PVT. Chronic high-fat diet not only impairs 5-HT inhibition of the ZI-PVT GABA transmission but also downregulates 5-HT excitation of PVT neurons. PVT-projecting dorsal raphe neurons express 5-HT and are inhibited by food deprivation.
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Affiliation(s)
- Qiying Ye
- Department of Psychology, Florida State University, Tallahassee, FL, USA
| | - Xiaobing Zhang
- Department of Psychology, Florida State University, Tallahassee, FL, USA
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van Galen KA, Ter Horst KW, Serlie MJ. Serotonin, food intake, and obesity. Obes Rev 2021; 22:e13210. [PMID: 33559362 PMCID: PMC8243944 DOI: 10.1111/obr.13210] [Citation(s) in RCA: 39] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/08/2020] [Revised: 12/28/2020] [Accepted: 12/28/2020] [Indexed: 12/16/2022]
Abstract
The role of serotonin in food intake has been studied for decades. Food intake is mainly regulated by two brain circuitries: (i) the homeostatic circuitry, which matches energy intake to energy expenditure, and (ii) the hedonic circuitry, which is involved in rewarding and motivational aspects of energy consumption. In the homeostatic circuitry, serotonergic signaling contributes to the integration of metabolic signals that convey the body's energy status and facilitates the ability to suppress food intake when homeostatic needs have been met. In the hedonic circuitry, serotonergic signaling may reduce reward-related, motivational food consumption. In contrast, peripherally acting serotonin promotes energy absorption and storage. Disturbed serotonergic signaling is associated with obesity, emphasizing the importance to understand the role of serotonergic signaling in food intake. However, unraveling the serotonin-mediated regulation of food intake is complex, as the effects of serotonergic signaling in different brain regions depend on the regional expression of serotonin receptor subtypes and downstream effects via connections to other brain regions. We therefore provide an overview of the effects of serotonergic signaling in brain regions of the homeostatic and hedonic regulatory systems on food intake. Furthermore, we discuss the disturbances in serotonergic signaling in obesity and its potential therapeutic implications.
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Affiliation(s)
- Katy A van Galen
- Department of Endocrinology and Metabolism, Amsterdam University Medical Centers, Amsterdam, The Netherlands
| | - Kasper W Ter Horst
- Department of Endocrinology and Metabolism, Amsterdam University Medical Centers, Amsterdam, The Netherlands
| | - Mireille J Serlie
- Department of Endocrinology and Metabolism, Amsterdam University Medical Centers, Amsterdam, The Netherlands
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Flores RA, Steinbach R, Pedroso JAB, Metzger M, Donato J, Paschoalini MA. Injections of the α-2 adrenoceptor agonist clonidine into the dorsal raphe nucleus increases food intake in satiated rats. Neuropharmacology 2020; 182:108397. [PMID: 33188843 DOI: 10.1016/j.neuropharm.2020.108397] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2020] [Revised: 11/04/2020] [Accepted: 11/07/2020] [Indexed: 10/23/2022]
Abstract
The present study aimed to evaluate the effects of pharmacological manipulation of α-adrenergic agonists in the dorsal raphe nucleus (DR) on food intake in satiated rats. Adult male Wistar rats with chronically implanted cannula in the DR were injected with adrenaline (AD) or noradrenaline (NA) (both at doses of 6, 20 and 60 nmol), or α-1 adrenergic agonist phenylephrine (PHE) or α-2 adrenergic agonist clonidine (CLO) (both at doses of 6 and 20 nmol). The injections were followed by the evaluation of ingestive behaviors. Food and water intake were evaluated for 60 min. Administration of AD and NA at 60 nmol and CLO at 20 nmol increased food intake and decreased latency to start consumption in satiated rats. The ingestive behavior was not significantly affected by PHE treatment in the DR. CLO treatment increased Fos expression in the arcuate nucleus (ARC) and paraventricular nucleus of the hypothalamus (PVN) in rats that were allowed to eat during the experimental recording (AF group). However, when food was not offered during the experiment (WAF group), PVN neurons were not activated, whereas, neuronal activity remained high in the ARC when compared to control group. Noteworthy, ARC POMC neurons expressed Fos in the AF group. However, double-labeled POMC/Fos cells were absent in the ARC of the WAF group, although an increase in Fos expression was observed in non-POMC cells after CLO injections in the WAF group. In conclusion, the data from the present study highlight that the pharmacological activation of DR α-adrenoceptors affects food intake in satiated rats. The feeding response evoked by CLO injections into DR was similar to that induced by NA or AD injections, suggesting that the hyperphagia after NA or AD treatment depends on α-2 adrenoceptors activation. Finally, we have demonstrated that CLO injections into DR impact neuronal activity in the ARC, possibly evoking a homeostatic response toward food intake.
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Affiliation(s)
- Rafael Appel Flores
- Department of Physiological Sciences, Center of Biological Sciences - CCB, Federal University of Santa Catarina (UFSC), 88040-970, Florianópolis, SC, Brazil.
| | - Renata Steinbach
- Department of Physiological Sciences, Center of Biological Sciences - CCB, Federal University of Santa Catarina (UFSC), 88040-970, Florianópolis, SC, Brazil.
| | - João A B Pedroso
- Department of Physiology & Biophysics, Institute of Biomedical Sciences, University of São Paulo, 05508-900, São Paulo, SP, Brazil.
| | - Martin Metzger
- Department of Physiology & Biophysics, Institute of Biomedical Sciences, University of São Paulo, 05508-900, São Paulo, SP, Brazil.
| | - José Donato
- Department of Physiology & Biophysics, Institute of Biomedical Sciences, University of São Paulo, 05508-900, São Paulo, SP, Brazil.
| | - Marta Aparecida Paschoalini
- Department of Physiological Sciences, Center of Biological Sciences - CCB, Federal University of Santa Catarina (UFSC), 88040-970, Florianópolis, SC, Brazil.
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Fan F, Yang M, Geng X, Ma X, Sun H. Effects of Restraint Water-Immersion Stress-Induced Gastric Mucosal Damage on Astrocytes and Neurons in the Nucleus Raphe Magnus of Rats via the ERK1/2 Signaling Pathway. Neurochem Res 2019; 44:1841-1850. [PMID: 31119435 DOI: 10.1007/s11064-019-02818-0] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2019] [Revised: 05/03/2019] [Accepted: 05/20/2019] [Indexed: 01/31/2023]
Abstract
Restraint water-immersion stress (RWIS) consists of psychological and physical stimulation, and it has been utilized in the research of gastric mucosal damage. It has been shown by previous studies that the nucleus raphe magnus (NRM) is closely involved in the gastrointestinal function, but its functions on the stress-induced gastric mucosal injury (SGMI) have not been thoroughly elucidated to date. Consequently, in this research, we aim to measure the expression of astrocytic glial fibrillary acidic protein (GFAP), neuronal c-Fos, and phosphorylation extracellular signal regulated kinase 1/2 (p-ERK1/2) in the process of RWIS with immunohistochemistry and western blot methods. What is more, we detect the relation between astrocytes and neurons throughout the stress procedure and explore the regulation of the ERK1/2 signaling pathway on the activity of astrocytes and neurons after RWIS. The results indicated that all three proteins expression multiplied following peaked 3 h substantially. The SMGI, astrocyte and neuron activity were affected after the astrocytotoxin L-A-aminohexanedioic acid (L-AA) and c-fos antisense oligonucleotide (ASO) injections. After the injection of PD98059, the gastric mucosal injury, astrocyte and neuron activity significantly fell off. These results suggested that RWIS-induced activity of astrocytes and neurons in the NRM may play a significant part in gastric mucosa damage via the ERK1/2 signaling pathway.
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Affiliation(s)
- Fangcheng Fan
- Key Laboratory of Animal Resistance Biology of Shandong Province, College of Life Science, Shandong Normal University, Jinan, 250014, China
| | - Mengzhu Yang
- Qingdao No. 31 Middle School, Qingdao, 266041, China
| | - Xiwen Geng
- Shandong Traditional Chinese Medicine University, Jinan, 250014, China
| | - Xiaoli Ma
- Central Laboratory, Jinan Central Hospital Affiliated to Shandong University, Jinan, 250013, China.
| | - Haiji Sun
- Key Laboratory of Animal Resistance Biology of Shandong Province, College of Life Science, Shandong Normal University, Jinan, 250014, China.
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