title: Mapping the cellular electrophysiology of rat sympathetic preganglionic neurones to their roles in cardiorespiratory reflex integration: a whole cell recording study in situ.
abstract: Sympathetic preganglionic neurones (SPNs) convey sympathetic activity flowing from the CNS to the periphery to reach the target organs. Although previous in vivo and in vitro cell recording studies have explored their electrophysiological characteristics, it has not been possible to relate these characteristics to their roles in cardiorespiratory reflex integration. We used the working heart-brainstem preparation to make whole cell patch clamp recordings from T3-4 SPNs (n = 98). These SPNs were classified by their distinct responses to activation of the peripheral chemoreflex, diving response and arterial baroreflex, allowing the discrimination of muscle vasoconstrictor-like (MVC(like), 39%) from cutaneous vasoconstrictor-like (CVC(like), 28%) SPNs. The MVC(like) SPNs have higher baseline firing frequencies (2.52 ± 0.33 Hz vs. CVC(like) 1.34 ± 0.17 Hz, P = 0.007). The CVC(like) have longer after-hyperpolarisations (314 ± 36 ms vs. MVC(like) 191 ± 13 ms, P < 0.001) and lower input resistance (346 ± 49 MΩ vs. MVC(like) 496 ± 41 MΩ, P < 0.05). MVC(like) firing was respiratory-modulated with peak discharge in the late inspiratory/early expiratory phase and this activity was generated by both a tonic and respiratory-modulated barrage of synaptic events that were blocked by intrathecal kynurenate. In contrast, the activity of CVC(like) SPNs was underpinned by rhythmical membrane potential oscillations suggestive of gap junctional coupling. Thus, we have related the intrinsic electrophysiological properties of two classes of SPNs in situ to their roles in cardiorespiratory reflex integration and have shown that they deploy different cellular mechanisms that are likely to influence how they integrate and shape the distinctive sympathetic outputs.
authors.affiliation: School of Physiology & Pharmacology, Bristol Heart Institute, Medical Sciences Building, University Walk, University of Bristol, Bristol, BS8 1TD, UK.
authors.forename: Alexey O
authors.initials: AO
authors.lastname: Stalbovskiy
authors.affiliation: School of Physiology & Pharmacology, Bristol Heart Institute, Medical Sciences Building, University Walk, University of Bristol, Bristol, BS8 1TD, UK Department of Engineering Mathematics, Merchant Venturers Building, Woodland Road, University of Bristol, Bristol, BS8 1UB, UK.
authors.forename: Linford J B
authors.initials: LJ
authors.lastname: Briant
authors.affiliation: School of Physiology & Pharmacology, Bristol Heart Institute, Medical Sciences Building, University Walk, University of Bristol, Bristol, BS8 1TD, UK.
authors.forename: Julian F R
authors.initials: JF
authors.lastname: Paton
authors.affiliation: School of Physiology & Pharmacology, Bristol Heart Institute, Medical Sciences Building, University Walk, University of Bristol, Bristol, BS8 1TD, UK Department of Anaesthesia, University Hospitals Bristol, Bristol, BS2 8HW, UK tony.pickering@bristol.ac.uk.
authors.forename: Anthony E
authors.initials: AE
authors.lastname: Pickering
mesh_terms: D000200:Action Potentials / Q000502:physiology*; D000818:Animals; D001339:Autonomic Fibers, Preganglionic / Q000502:physiology*; D017704:Baroreflex / Q000502:physiology*; D066298:In Vitro Techniques; D008297:Male; D009415:Nerve Net / Q000502:physiology; D009476:Neurons, Efferent / Q000502:physiology*; D051381:Rats; D017208:Rats, Wistar; D015656:Respiratory Mechanics / Q000502:physiology*; D013116:Spinal Cord / Q000502:physiology*; D013564:Sympathetic Nervous System / Q000502:physiology*; D018511:Systems Integration