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Housley SN, Gardolinski EA, Nardelli P, Reed J, Rich MM, Cope TC. Mechanosensory encoding in ex vivo muscle-nerve preparations. Exp Physiol 2024; 109:35-44. [PMID: 37119460 PMCID: PMC10613129 DOI: 10.1113/ep090763] [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: 12/23/2022] [Accepted: 04/12/2023] [Indexed: 05/01/2023]
Abstract
Our objective was to evaluate an ex vivo muscle-nerve preparation used to study mechanosensory signalling by low threshold mechanosensory receptors (LTMRs). Specifically, we aimed to assess how well the ex vivo preparation represents in vivo firing behaviours of the three major LTMR subtypes of muscle primary sensory afferents, namely type Ia and II muscle spindle (MS) afferents and type Ib tendon organ afferents. Using published procedures for ex vivo study of LTMRs in mouse hindlimb muscles, we replicated earlier reports on afferent firing in response to conventional stretch paradigms applied to non-contracting, that is passive, muscle. Relative to in vivo studies, stretch-evoked firing for confirmed MS afferents in the ex vivo preparation was markedly reduced in firing rate and deficient in encoding dynamic features of muscle stretch. These deficiencies precluded conventional means of discriminating type Ia and II afferents. Muscle afferents, including confirmed Ib afferents were often indistinguishable based on their similar firing responses to the same physiologically relevant stretch paradigms. These observations raise uncertainty about conclusions drawn from earlier ex vivo studies that either attribute findings to specific afferent types or suggest an absence of treatment effects on dynamic firing. However, we found that replacing the recording solution with bicarbonate buffer resulted in afferent firing rates and profiles more like those seen in vivo. Improving representation of the distinctive sensory encoding properties in ex vivo muscle-nerve preparations will promote accuracy in assigning molecular markers and mechanisms to heterogeneous types of muscle mechanosensory neurons.
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Affiliation(s)
- Stephen N. Housley
- School of Biological SciencesGeorgia Institute of TechnologyAtlantaGAUSA
| | | | - Paul Nardelli
- School of Biological SciencesGeorgia Institute of TechnologyAtlantaGAUSA
| | - J'Ana Reed
- School of Biological SciencesGeorgia Institute of TechnologyAtlantaGAUSA
| | - Mark M. Rich
- Department of Neuroscience, Cell Biology and PhysiologyWright State UniversityDaytonOHUSA
| | - Timothy C. Cope
- School of Biological SciencesGeorgia Institute of TechnologyAtlantaGAUSA
- W.H. Coulter Department of Biomedical EngineeringEmory University and Georgia Institute of Technology, Georgia Institute of TechnologyAtlantaGAUSA
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Sharma B, Roy A, Sengupta T, Vishwakarma LC, Singh A, Netam R, Nag TC, Akhtar N, Mallick HN. Acute sleep deprivation induces synaptic remodeling at the soleus muscle neuromuscular junction in rats. Sleep 2023; 46:zsac229. [PMID: 36130235 DOI: 10.1093/sleep/zsac229] [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: 02/28/2022] [Revised: 08/03/2022] [Indexed: 07/26/2023] Open
Abstract
Sleep is important for cognitive and physical performance. Sleep deprivation not only affects neural functions but also results in muscular fatigue. A good night's sleep reverses these functional derangements caused by sleep deprivation. The role of sleep in brain function has been extensively studied. However, its role in neuromuscular junction (NMJ) or skeletal muscle morphology is sparsely addressed although skeletal muscle atonia and suspended thermoregulation during rapid eye movement sleep possibly provide a conducive environment for the muscle to rest and repair; somewhat similar to slow-wave sleep for synaptic downscaling. In the present study, we have investigated the effect of 24 h sleep deprivation on the NMJ morphology and neurochemistry using electron microscopy and immunohistochemistry in the rat soleus muscle. Acute sleep deprivation altered synaptic ultra-structure viz. mitochondria, synaptic vesicle, synaptic proteins, basal lamina, and junctional folds needed for neuromuscular transmission. Further acute sleep deprivation showed the depletion of the neurotransmitter acetylcholine and the overactivity of its degrading enzyme acetylcholine esterase at the NMJ. The impact of sleep deprivation on synaptic homeostasis in the brain has been extensively reported recently. The present evidence from our studies shows new information on the role of sleep on the NMJ homeostasis and its functioning.
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Affiliation(s)
- Binney Sharma
- Department of Physiology, All India Institute of Medical Sciences, New Delhi, India
| | - Avishek Roy
- Department of Physiology, All India Institute of Medical Sciences, New Delhi, India
| | - Trina Sengupta
- Department of Physiology, All India Institute of Medical Sciences, New Delhi, India
- Department of Physiology, All India Institute of Medical Sciences, Jodhpur, Rajasthan, India
| | | | - Anuraag Singh
- Department of Anatomy, All India Institute of Medical Sciences, New Delhi, India
| | - Ritesh Netam
- Department of Physiology, All India Institute of Medical Sciences, New Delhi, India
| | - Tapas Chandra Nag
- Department of Physiology, Faculty of Medicine & Health Sciences, SGT University, Gurugram, Haryana, India
| | - Nasreen Akhtar
- Department of Physiology, All India Institute of Medical Sciences, New Delhi, India
| | - Hruda Nanda Mallick
- Department of Physiology, All India Institute of Medical Sciences, New Delhi, India
- Department of Physiology, Faculty of Medicine & Health Sciences, SGT University, Gurugram, Haryana, India
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