Axonal branching patterns and funicular trajectories of raphespinal sympathoinhibitory neurons

Shaun Morrison, G. L. Gebber

Research output: Contribution to journalArticle

58 Citations (Scopus)

Abstract

We studied axonal branching patterns and funicular trajectories of cat medullary raphespinal neurons with spontaneous activity related to inferior cardiac postganglionic sympathetic nerve discharge (as demonstrated with spike-triggered averaging). These neurons were excited by raising carotid sinus pressure. We have classified these neurons as sympathoinhibitory in function and refer to them here as RS neurons. Microstimulation of the second thoracic spinal segment (T2) antidromically activated RS neurons. The longest-latency antidromic responses were elicited with the lowest-threshold current from sites in the intermediolateral nucleus (IML). This observation suggests that RS neurons innervated IML. Most RS neurons activated from T2 were also antidromically activated by stimulation of a more caudal thoracic spinal segment (T6 or T12). Time-controlled collision of action potentials evoked by stimulation at two thoracic levels allowed us to distinguish activation of an axonal branch in T2 from that of the main axon coursing through T2 to the more caudal thoracic level. Of those RS axons that branched in T2, 78% descended at least as far caudal as T6, whereas 65% reached T12. The axonal projections of other RS neurons that innervated T2 were restricted to no more than two consecutive thoracic spinal segments. Antidromic mapping of T2 revealed that the axons of RS neurons coursed through the dorsolateral, ventral, or ventrolateral funiculus to innervate the ipsilateral and/or contralateral IML. The conduction velocities of dorsolateral and ventral RS axons indicated that they were finely myelinated. The data demonstrate the existence of RS neurons with restricted and widespread axonal branching patterns, supporting the view that the medullary raphe complex is capable of regional as well as global inhibitory control over spinal sympathetic outflow.

Original languageEnglish (US)
Pages (from-to)759-772
Number of pages14
JournalJournal of Neurophysiology
Volume53
Issue number3
StatePublished - 1985
Externally publishedYes

Fingerprint

Neurons
Thorax
Axons
Carotid Sinus
Action Potentials
Reaction Time
Cats
Pressure
Spinal Cord Lateral Horn

ASJC Scopus subject areas

  • Physiology
  • Neuroscience(all)

Cite this

Axonal branching patterns and funicular trajectories of raphespinal sympathoinhibitory neurons. / Morrison, Shaun; Gebber, G. L.

In: Journal of Neurophysiology, Vol. 53, No. 3, 1985, p. 759-772.

Research output: Contribution to journalArticle

@article{3affe7fdadb24c16a5e016e06f8fe6f4,
title = "Axonal branching patterns and funicular trajectories of raphespinal sympathoinhibitory neurons",
abstract = "We studied axonal branching patterns and funicular trajectories of cat medullary raphespinal neurons with spontaneous activity related to inferior cardiac postganglionic sympathetic nerve discharge (as demonstrated with spike-triggered averaging). These neurons were excited by raising carotid sinus pressure. We have classified these neurons as sympathoinhibitory in function and refer to them here as RS neurons. Microstimulation of the second thoracic spinal segment (T2) antidromically activated RS neurons. The longest-latency antidromic responses were elicited with the lowest-threshold current from sites in the intermediolateral nucleus (IML). This observation suggests that RS neurons innervated IML. Most RS neurons activated from T2 were also antidromically activated by stimulation of a more caudal thoracic spinal segment (T6 or T12). Time-controlled collision of action potentials evoked by stimulation at two thoracic levels allowed us to distinguish activation of an axonal branch in T2 from that of the main axon coursing through T2 to the more caudal thoracic level. Of those RS axons that branched in T2, 78{\%} descended at least as far caudal as T6, whereas 65{\%} reached T12. The axonal projections of other RS neurons that innervated T2 were restricted to no more than two consecutive thoracic spinal segments. Antidromic mapping of T2 revealed that the axons of RS neurons coursed through the dorsolateral, ventral, or ventrolateral funiculus to innervate the ipsilateral and/or contralateral IML. The conduction velocities of dorsolateral and ventral RS axons indicated that they were finely myelinated. The data demonstrate the existence of RS neurons with restricted and widespread axonal branching patterns, supporting the view that the medullary raphe complex is capable of regional as well as global inhibitory control over spinal sympathetic outflow.",
author = "Shaun Morrison and Gebber, {G. L.}",
year = "1985",
language = "English (US)",
volume = "53",
pages = "759--772",
journal = "Journal of Neurophysiology",
issn = "0022-3077",
publisher = "American Physiological Society",
number = "3",

}

TY - JOUR

T1 - Axonal branching patterns and funicular trajectories of raphespinal sympathoinhibitory neurons

AU - Morrison, Shaun

AU - Gebber, G. L.

PY - 1985

Y1 - 1985

N2 - We studied axonal branching patterns and funicular trajectories of cat medullary raphespinal neurons with spontaneous activity related to inferior cardiac postganglionic sympathetic nerve discharge (as demonstrated with spike-triggered averaging). These neurons were excited by raising carotid sinus pressure. We have classified these neurons as sympathoinhibitory in function and refer to them here as RS neurons. Microstimulation of the second thoracic spinal segment (T2) antidromically activated RS neurons. The longest-latency antidromic responses were elicited with the lowest-threshold current from sites in the intermediolateral nucleus (IML). This observation suggests that RS neurons innervated IML. Most RS neurons activated from T2 were also antidromically activated by stimulation of a more caudal thoracic spinal segment (T6 or T12). Time-controlled collision of action potentials evoked by stimulation at two thoracic levels allowed us to distinguish activation of an axonal branch in T2 from that of the main axon coursing through T2 to the more caudal thoracic level. Of those RS axons that branched in T2, 78% descended at least as far caudal as T6, whereas 65% reached T12. The axonal projections of other RS neurons that innervated T2 were restricted to no more than two consecutive thoracic spinal segments. Antidromic mapping of T2 revealed that the axons of RS neurons coursed through the dorsolateral, ventral, or ventrolateral funiculus to innervate the ipsilateral and/or contralateral IML. The conduction velocities of dorsolateral and ventral RS axons indicated that they were finely myelinated. The data demonstrate the existence of RS neurons with restricted and widespread axonal branching patterns, supporting the view that the medullary raphe complex is capable of regional as well as global inhibitory control over spinal sympathetic outflow.

AB - We studied axonal branching patterns and funicular trajectories of cat medullary raphespinal neurons with spontaneous activity related to inferior cardiac postganglionic sympathetic nerve discharge (as demonstrated with spike-triggered averaging). These neurons were excited by raising carotid sinus pressure. We have classified these neurons as sympathoinhibitory in function and refer to them here as RS neurons. Microstimulation of the second thoracic spinal segment (T2) antidromically activated RS neurons. The longest-latency antidromic responses were elicited with the lowest-threshold current from sites in the intermediolateral nucleus (IML). This observation suggests that RS neurons innervated IML. Most RS neurons activated from T2 were also antidromically activated by stimulation of a more caudal thoracic spinal segment (T6 or T12). Time-controlled collision of action potentials evoked by stimulation at two thoracic levels allowed us to distinguish activation of an axonal branch in T2 from that of the main axon coursing through T2 to the more caudal thoracic level. Of those RS axons that branched in T2, 78% descended at least as far caudal as T6, whereas 65% reached T12. The axonal projections of other RS neurons that innervated T2 were restricted to no more than two consecutive thoracic spinal segments. Antidromic mapping of T2 revealed that the axons of RS neurons coursed through the dorsolateral, ventral, or ventrolateral funiculus to innervate the ipsilateral and/or contralateral IML. The conduction velocities of dorsolateral and ventral RS axons indicated that they were finely myelinated. The data demonstrate the existence of RS neurons with restricted and widespread axonal branching patterns, supporting the view that the medullary raphe complex is capable of regional as well as global inhibitory control over spinal sympathetic outflow.

UR - http://www.scopus.com/inward/record.url?scp=0021955064&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=0021955064&partnerID=8YFLogxK

M3 - Article

C2 - 3981237

AN - SCOPUS:0021955064

VL - 53

SP - 759

EP - 772

JO - Journal of Neurophysiology

JF - Journal of Neurophysiology

SN - 0022-3077

IS - 3

ER -