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Silwal P, Singhal P, Senecal JM, Senecal JE, Lynn BD, Nagy JI. Patterns of connexin36 and eGFP reporter expression among motoneurons in spinal sexually dimorphic motor nuclei in mouse. INTERNATIONAL JOURNAL OF PHYSIOLOGY, PATHOPHYSIOLOGY AND PHARMACOLOGY 2024; 16:55-76. [PMID: 39021417 PMCID: PMC11249853 DOI: 10.62347/ogwv9376] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/14/2024] [Accepted: 05/06/2024] [Indexed: 07/20/2024]
Abstract
BACKGROUND Sexually dimorphic spinal motoneurons (MNs) in the dorsomedial nucleus (DMN) and dorsolateral nucleus (DLN) as well as those in the cremaster nucleus are involved in reproductive behaviours, and the cremaster nucleus additionally contributes to testicular thermoregulation. It has been reported that MNs in DMN and DLN are extensively linked by gap junctions forming electrical synapses composed of connexin36 (Cx36) and there is evidence that subpopulation of MNs in the cremaster nucleus are also electrically coupled by these synapses. METHODOLOGY We used immunofluorescence methods to detect enhanced green fluorescent protein (eGFP) reporter for Cx36 expression in these motor nuclei. RESULTS We document in male mice that about half the MNs in each of DMN and DLN express eGFP, while the remaining half do not. Further, we found that the eGFP+ vs. eGFP- subsets of MNs in each of these motor nuclei innervate different target muscles; eGFP+ MNs in DMN and DLN project to sexually dimorphic bulbocavernosus and ischiocavernosus muscles, while the eGFP- subsets project to sexually non-dimorphic anal and external urethral sphincter muscles. Similarly, eGFP+ vs. eGFP- cremaster MNs were found to project to anatomically distinct portions of the cremaster muscle. By immunofluorescence, nearly all motoneurons in both DMN and DLN displayed punctate labelling for Cx36, including at eGFP+/eGFP+, eGFP+/eGFP- and eGFP-/eGFP- cell appositions. CONCLUSIONS Most if not all motoneurons in DMN and DLN are electrically coupled, including sexually dimorphic and non-dimorphic motoneurons with each other, despite absence of eGFP reporter in the non-dimorphic populations in these nuclei that have selective projections to sexually non-dimorphic target muscles.
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Affiliation(s)
- Prabhisha Silwal
- Department of Physiology and Pathophysiology, Rady Faculty of Health Sciences, Max Rady College of Medicine, University of Manitoba Winnipeg, Manitoba R3E 0J9, Canada
| | - Pratyaksh Singhal
- Department of Physiology and Pathophysiology, Rady Faculty of Health Sciences, Max Rady College of Medicine, University of Manitoba Winnipeg, Manitoba R3E 0J9, Canada
| | - Joanne Mm Senecal
- Department of Physiology and Pathophysiology, Rady Faculty of Health Sciences, Max Rady College of Medicine, University of Manitoba Winnipeg, Manitoba R3E 0J9, Canada
| | - Julie Em Senecal
- Department of Physiology and Pathophysiology, Rady Faculty of Health Sciences, Max Rady College of Medicine, University of Manitoba Winnipeg, Manitoba R3E 0J9, Canada
| | - Bruce D Lynn
- Department of Physiology and Pathophysiology, Rady Faculty of Health Sciences, Max Rady College of Medicine, University of Manitoba Winnipeg, Manitoba R3E 0J9, Canada
| | - James I Nagy
- Department of Physiology and Pathophysiology, Rady Faculty of Health Sciences, Max Rady College of Medicine, University of Manitoba Winnipeg, Manitoba R3E 0J9, Canada
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Recabal-Beyer A, Tavakoli H, M M Senecal J, Stecina K, Nagy JI. Interrelationships between spinal sympathetic preganglionic neurons, autonomic systems and electrical synapses formed by connexin36-containing gap junctions. Neuroscience 2023:S0306-4522(23)00220-8. [PMID: 37225049 DOI: 10.1016/j.neuroscience.2023.05.009] [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: 11/23/2022] [Revised: 04/24/2023] [Accepted: 05/14/2023] [Indexed: 05/26/2023]
Abstract
Spinal sympathetic preganglionic neurons (SPNs) are among the many neuronal populations in the mammalian central nervous system (CNS) where there is evidence for electrical coupling between cell pairs linked by gap junctions composed of connexin36 (Cx36). Understanding the organization of this coupling in relation to autonomic functions of spinal sympathetic systems requires knowledge of how these junctions are deployed among SPNs. Here, we document the distribution of immunofluorescence detection of Cx36 among SPNs identified by immunolabelling of their various markers, including choline acetyltransferase, nitric oxide and peripherin in adult and developing mouse and rat. In adult animals, labelling of Cx36 was exclusively punctate and dense concentrations of Cx36-puncta were distributed along the entire length of the spinal thoracic intermediolateral cell column (IML). These puncta were also seen in association with SPN dendritic processes in the lateral funiculus, the intercalated and central autonomic areas and those within and extending medially from the IML. All labelling for Cx36 was absent in spinal cords of Cx36 knockout mice. High densities of Cx36-puncta were already evident among clusters of SPNs in the IML of mouse and rat at postnatal days 10-12. In Cx36BAC::eGFP mice, eGFP reporter was absent in SPNs, thus representing false negative detection, but was localized to some glutamatergic and GABAergic synaptic terminals. Some eGFP+ terminals were found contacting SPN dendrites. These results indicate widespread Cx36 expression in SPNs, further supporting evidence of electrical coupling between these cells, and suggest that SPNs are innervated by neurons that themselves may be electrically coupled.
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Affiliation(s)
- A Recabal-Beyer
- Department of Physiology and Pathophysiology, Max Rady College of Medicine, Rady Faculty of Health Sciences, University of Manitoba, Winnipeg, Canada R3E 0J9
| | - H Tavakoli
- Department of Physiology and Pathophysiology, Max Rady College of Medicine, Rady Faculty of Health Sciences, University of Manitoba, Winnipeg, Canada R3E 0J9
| | - J M M Senecal
- Department of Physiology and Pathophysiology, Max Rady College of Medicine, Rady Faculty of Health Sciences, University of Manitoba, Winnipeg, Canada R3E 0J9
| | - K Stecina
- Department of Physiology and Pathophysiology, Max Rady College of Medicine, Rady Faculty of Health Sciences, University of Manitoba, Winnipeg, Canada R3E 0J9
| | - J I Nagy
- Department of Physiology and Pathophysiology, Max Rady College of Medicine, Rady Faculty of Health Sciences, University of Manitoba, Winnipeg, Canada R3E 0J9.
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Cook LG, Mitschow LC. Beyond the Polygraph: Deception Detection and the Autonomic Nervous System. Fed Pract 2019; 36:316-321. [PMID: 31384120 PMCID: PMC6654171] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
The polygraph and other emerging technologies are used to aid in the interrogation and screening of employees, but examiners and physicians should be aware that results are vulnerable to inaccuracies in subjects with autonomic disorders and may be confounded by multiple medications.
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Affiliation(s)
- Lcdr Glen Cook
- is a Staff Neurologist, and is a Psychiatry Resident, both at Naval Medical Center Portsmouth in Virginia
| | - Lt Charles Mitschow
- is a Staff Neurologist, and is a Psychiatry Resident, both at Naval Medical Center Portsmouth in Virginia
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Mahadi KM, Lall VK, Deuchars SA, Deuchars J. Cardiovascular autonomic effects of transcutaneous auricular nerve stimulation via the tragus in the rat involve spinal cervical sensory afferent pathways. Brain Stimul 2019; 12:1151-1158. [PMID: 31129152 DOI: 10.1016/j.brs.2019.05.002] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2018] [Revised: 04/17/2019] [Accepted: 05/02/2019] [Indexed: 02/08/2023] Open
Abstract
BACKGROUND Electrical stimulation on select areas of the external auricular dermatome influences the autonomic nervous system. It has been postulated that activation of the Auricular Branch of the Vagus Nerve (ABVN) mediates such autonomic changes. However, the underlying neural pathways mediating these effects are unknown and, further, our understanding of the anatomical distribution of the ABVN in the auricle has now been questioned. OBJECTIVE To investigate the effects of electrical stimulation of the tragus on autonomic outputs in the rat and probe the underlying neural pathways. METHODS Central neuronal projections from nerves innervating the external auricle were investigated by injections of the transganglionic tracer cholera toxin B chain (CTB) into the right tragus of Wistar rats. Physiological recordings of heart rate, perfusion pressure, respiratory rate and sympathetic nerve activity were made in an anaesthetic free Working Heart Brainstem Preparation (WHBP) of the rat and changes in response to electrical stimulation of the tragus analysed. RESULTS Neuronal tracing from the tragus revealed that the densest CTB labelling was within laminae III-IV of the dorsal horn of the upper cervical spinal cord, ipsilateral to the injection sites. In the medulla oblongata, CTB labelled afferents were observed in the paratrigeminal nucleus, spinal trigeminal tract and cuneate nucleus. Surprisingly, only sparse labelling was observed in the vagal afferent termination site, the nucleus tractus solitarius. Recordings made from rats at night time revealed more robust sympathetic activity in comparison to day time rats, thus subsequent experiments were conducted in rats at night time. Electrical stimulation was delivered across the tragus for 5 min. Direct recording from the sympathetic chain revealed a central sympathoinhibition by up to 36% following tragus stimulation. Sympathoinhibition remained following sectioning of the cervical vagus nerve ipsilateral to the stimulation site, but was attenuated by sectioning of the upper cervical afferent nerve roots. CONCLUSIONS Inhibition of the sympathetic nervous system activity upon electrical stimulation of the tragus in the rat is mediated at least in part through sensory afferent projections to the upper cervical spinal cord. This challenges the notion that tragal stimulation is mediated by the auricular branch of the vagus nerve and suggests that alternative mechanisms may be involved.
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Affiliation(s)
- K M Mahadi
- Faculty of Biological Sciences, School of Biomedical Sciences, University of Leeds, United Kingdom; Drug and Herbal Research Centre, Faculty of Pharmacy, Universiti Kebangsaan Malaysia, Kuala Lumpur, Malaysia
| | - V K Lall
- Faculty of Biological Sciences, School of Biomedical Sciences, University of Leeds, United Kingdom
| | - S A Deuchars
- Faculty of Biological Sciences, School of Biomedical Sciences, University of Leeds, United Kingdom.
| | - J Deuchars
- Faculty of Biological Sciences, School of Biomedical Sciences, University of Leeds, United Kingdom.
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Lall VK, Bruce G, Voytenko L, Drinkhill M, Wellershaus K, Willecke K, Deuchars J, Deuchars SA. Physiologic regulation of heart rate and blood pressure involves connexin 36-containing gap junctions. FASEB J 2017; 31:3966-3977. [PMID: 28533325 PMCID: PMC5566179 DOI: 10.1096/fj.201600919rr] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2016] [Accepted: 05/01/2017] [Indexed: 01/15/2023]
Abstract
Chronically elevated sympathetic nervous activity underlies many cardiovascular diseases. Elucidating the mechanisms contributing to sympathetic nervous system output may reveal new avenues of treatment. The contribution of the gap junctional protein connexin 36 (Cx36) to the regulation of sympathetic activity and thus blood pressure and heart rate was determined using a mouse with specific genetic deletion of Cx36. Ablation of the Cx36 protein was confirmed in sympathetic preganglionic neurons of Cx36-knockout (KO) mice. Telemetric analysis from conscious Cx36 KO mice revealed higher variance in heart rate and blood pressure during rest and activity compared to wild-type (WT) mice, and smaller responses to chemoreceptor activation when anesthetized. In the working heart-brain stem preparation of the Cx36-KO mouse, respiratory-coupled sympathetic nerve discharge was attenuated and responses to chemoreceptor stimulation and noxious stimulation were blunted compared to WT mice. Using whole cell patch recordings, sympathetic preganglionic neurons in spinal cord slices of Cx36-KO mice displayed lower levels of spikelet activity compared to WT mice, indicating reduced gap junction coupling between neurons. Cx36 deletion therefore disrupts normal regulation of sympathetic outflow with effects on cardiovascular parameters.-Lall, V. K., Bruce, G., Voytenko, L., Drinkhill, M., Wellershaus, K., Willecke, K., Deuchars, J., Deuchars, S. A. Physiologic regulation of heart rate and blood pressure involves connexin 36-containing gap junctions.
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Affiliation(s)
- Varinder K Lall
- Faculty of Biological Sciences, School of Biomedical Sciences, University of Leeds, Leeds, United Kingdom
| | - Gareth Bruce
- Faculty of Biological Sciences, School of Biomedical Sciences, University of Leeds, Leeds, United Kingdom
| | - Larysa Voytenko
- Faculty of Biological Sciences, School of Biomedical Sciences, University of Leeds, Leeds, United Kingdom
| | - Mark Drinkhill
- Division of Cardiovascular and Diabetes Research, Institute of Cardiovascular and Metabolic Medicine, University of Leeds, Leeds, United Kingdom
| | - Kerstin Wellershaus
- Life and Medical Sciences Institute (LIMES), University of Bonn, Bonn, Germany
| | - Klaus Willecke
- Life and Medical Sciences Institute (LIMES), University of Bonn, Bonn, Germany
| | - Jim Deuchars
- Faculty of Biological Sciences, School of Biomedical Sciences, University of Leeds, Leeds, United Kingdom
| | - Susan A Deuchars
- Faculty of Biological Sciences, School of Biomedical Sciences, University of Leeds, Leeds, United Kingdom;
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Deuchars SA, Lall VK. Sympathetic preganglionic neurons: properties and inputs. Compr Physiol 2016; 5:829-69. [PMID: 25880515 DOI: 10.1002/cphy.c140020] [Citation(s) in RCA: 44] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
The sympathetic nervous system comprises one half of the autonomic nervous system and participates in maintaining homeostasis and enabling organisms to respond in an appropriate manner to perturbations in their environment, either internal or external. The sympathetic preganglionic neurons (SPNs) lie within the spinal cord and their axons traverse the ventral horn to exit in ventral roots where they form synapses onto postganglionic neurons. Thus, these neurons are the last point at which the central nervous system can exert an effect to enable changes in sympathetic outflow. This review considers the degree of complexity of sympathetic control occurring at the level of the spinal cord. The morphology and targets of SPNs illustrate the diversity within this group, as do their diverse intrinsic properties which reveal some functional significance of these properties. SPNs show high degrees of coupled activity, mediated through gap junctions, that enables rapid and coordinated responses; these gap junctions contribute to the rhythmic activity so critical to sympathetic outflow. The main inputs onto SPNs are considered; these comprise afferent, descending, and interneuronal influences that themselves enable functionally appropriate changes in SPN activity. The complexity of inputs is further demonstrated by the plethora of receptors that mediate the different responses in SPNs; their origins and effects are plentiful and diverse. Together these different inputs and the intrinsic and coupled activity of SPNs result in the rhythmic nature of sympathetic outflow from the spinal cord, which has a variety of frequencies that can be altered in different conditions.
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Affiliation(s)
- Susan A Deuchars
- School of Biomedical Sciences, University of Leeds, Leeds, United Kingdom
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McCarthy S. Malaria Prevention, Mefloquine Neurotoxicity, Neuropsychiatric Illness, and Risk-Benefit Analysis in the Australian Defence Force. J Parasitol Res 2015; 2015:287651. [PMID: 26793391 PMCID: PMC4697095 DOI: 10.1155/2015/287651] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2015] [Accepted: 09/13/2015] [Indexed: 11/17/2022] Open
Abstract
The Australian Defence Force (ADF) has used mefloquine for malaria chemoprophylaxis since 1990. Mefloquine has been found to be a plausible cause of a chronic central nervous system toxicity syndrome and a confounding factor in the diagnosis of existing neuropsychiatric illnesses prevalent in the ADF such as posttraumatic stress disorder and traumatic brain injury. Overall health risks appear to have been mitigated by restricting the drug's use; however serious risks were realised when significant numbers of ADF personnel were subjected to clinical trials involving the drug. The full extent of the exposure, health impacts for affected individuals, and consequences for ADF health management including mental health are not yet known, but mefloquine may have caused or aggravated neuropsychiatric illness in large numbers of patients who were subsequently misdiagnosed and mistreated or otherwise failed to receive proper care. Findings in relation to chronic mefloquine neurotoxicity were foreseeable, but this eventuality appears not to have been considered during risk-benefit analyses. Thorough analysis by the ADF would have identified this long-term risk as well as other qualitative risk factors. Historical exposure of ADF personnel to mefloquine neurotoxicity now also necessitates ongoing risk monitoring and management in the overall context of broader health policies.
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Affiliation(s)
- Stuart McCarthy
- Headquarters 2nd Division, Australian Army, Randwick Barracks, Randwick, NSW 2031, Australia
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Deuchars SA. How sympathetic are your spinal cord circuits? Exp Physiol 2015; 100:365-71. [PMID: 25655449 DOI: 10.1113/ep085031] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2014] [Accepted: 01/29/2015] [Indexed: 12/21/2022]
Abstract
NEW FINDINGS What is the topic of this review? This review focuses on the role of gap junctions and interneurones in sympathetic control at the spinal cord level. What advances does it highlight? The review considers the importance of these local spinal circuits in contributing to rhythmic autonomic activity and enabling appropriate responses to homeostatic perturbations. Sympathetic control of end organs relies on the activity of sympathetic preganglionic neurones (SPNs) within the spinal cord. These SPNs exhibit heterogeneity with respect to function, neurochemistry, location, descending inputs and patterns of activity. Part of this heterogeneity is bestowed by local spinal circuitry. Our understanding of the role of these local circuits, including the significance of connections between the SPNs themselves through specialized gap junctions, is patchy. This report focuses on interneurones and gap junctions within these circuits. Gap junctions play a role in sympathetic control; they are located on SPNs in the intermediolateral cell column. Mefloquine, a chemical that blocks these gap junctions, reduces local rhythmic activity in the spinal cord slice and disrupts autonomic control in the working heart-brainstem preparation. The role that these gap junctions may play in health and disease in adult animals remains to be elucidated fully. Presympathetic interneurones are located in laminae V, VII and X and the intermediolateral cell column; those in lamina X are GABAergic and directly inhibit SPNs. The GABAergic inputs onto SPNs exert their effects through activation of synaptic and extrasynaptic receptors, which stabilize the membrane at negative potentials. The GABAergic interneurones contribute to rhythmic patterns of activity that can be generated in the spinal cord, because bicuculline reduces network oscillatory activity. These studies indicate that local spinal cord circuitry is critical in enabling appropriate levels and patterning of activity in sympathetic outflow. We need to understand how these circuits may be harnessed in the situation of spinal cord injury.
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Affiliation(s)
- Susan A Deuchars
- School of Biomedical Sciences, University of Leeds, Leeds, LS2 9JT, UK
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