Vagal afferent inhibition of primate thoracic spinothalamic neurons
W. S. Ammons, R. W. Blair and R. D. Foreman Spinothalamic (ST) neurons in the C8-T5 segments of the spinal cord were examined for responses to electrical stimulation of the left thoracic vagus nerve (LTV). Seventy-one ST neurons were studied in 39 anesthetized monkeys (Macaca fascicularis). Each neu...
Gespeichert in:
Veröffentlicht in: | Journal of neurophysiology 1983-10, Vol.50 (4), p.926-940 |
---|---|
Hauptverfasser: | , , |
Format: | Artikel |
Sprache: | eng |
Schlagworte: | |
Online-Zugang: | Volltext |
Tags: |
Tag hinzufügen
Keine Tags, Fügen Sie den ersten Tag hinzu!
|
Zusammenfassung: | W. S. Ammons, R. W. Blair and R. D. Foreman
Spinothalamic (ST) neurons in the C8-T5 segments of the spinal cord were
examined for responses to electrical stimulation of the left thoracic vagus
nerve (LTV). Seventy-one ST neurons were studied in 39 anesthetized monkeys
(Macaca fascicularis). Each neuron could be excited by manipulation of its
somatic field and by electrical stimulation of cardiopulmonary sympathetic
afferent fibers. LTV stimulation resulted in inhibition of the background
activity of 43 (61%) ST neurons. Nine (13%) were excited, 3 (4%) were
excited and then inhibited, while 16 (22%) did not respond. There was
little difference among these groups in terms of the type of somatic or
sympathetic afferent input although inhibited cells tended to be more
prevalent in the more superficial laminae. The degree of inhibition
resulting from LTV stimulation was related, in a linear fashion, to the
magnitude of cell activity before stimulation. LTV inhibition of background
activity was similar among wide dynamic range, high threshold, and
high-threshold cells with inhibitory hair input. Any apparent differences
in LTV inhibitory effects among these groups were accounted for by the
differences in ongoing cell activity as predicted by linear regression
analysis. LTV stimulation inhibited responses of 32 of 32 ST cells to
somatic stimuli. In most cases the stimulus was a noxious pinch; however,
LTV stimulation also inhibited responses to innocuous stimuli such as hair
movement. Bilateral cervical vagotomy abolished the inhibitory effect of
LTV stimulation on background activity (six cells) or responses to somatic
stimuli (seven cells). Stimulation of the cardiac branch of the vagus
inhibited activity of three cells to a similar degree as LTV stimulation,
while stimulation of the vagus below the heart was ineffective in reducing
activity of 10 cells. We conclude that LTV stimulation alters activity of
ST neurons in the upper thoracic spinal cord. Vagal inhibition of ST cell
activity was due to stimulation of cardiopulmonary vagal afferent fibers
coursing to the brain stem, which appear to activate descending inhibitory
spinal pathways. Vagal afferent activity may participate in processing of
somatosensory information as well as information related to cardiac pain. |
---|---|
ISSN: | 0022-3077 1522-1598 |
DOI: | 10.1152/jn.1983.50.4.926 |