Cardiac and abdominal vagal afferent inhibition of primate T9-S1 spinothalamic cells.
Effects of electrically stimulating vagal afferents were determined on lumbosacral spinothalamic tract (STT) neurons in the T9-S1 segments. Stimulating left or right vagal afferents inhibited 20 (50%) and excited 4 (10%) of 40 STT neurons. Vagal stimulation reduced activity of the 20 inhibited cells by 71 +/- 6% and reduced the average activity of all 40 STT neurons by 28% from 11.5 +/- 1.3 to 8.3 +/- 1.4 impulses/s (P less than 0.01). Effects of activating thoracic and abdominal or just abdominal vagal afferents were also determined. Stimulating right abdominal vagal afferents inhibited 4 (11%), excited 1 (3%), and did not affect 30 (86%) of the STT neurons and overall did not significantly affect STT cell activity. In contrast, in 33 of these cells stimulation of afferents in the right cervical vagus inhibited 16 (48%), excited 2 (6%), and did not affect 15 (45%) neurons and overall significantly reduced cell activity by 29% (P less than 0.01). These data and those of Ammons et al. (J. Neurophysiol. 50: 926-940, 1983; Circ Res. 53: 603-612, 1983; J. Neurophysiol. 54: 73-89, 1985) suggest that cardiopulmonary but not abdominal vagal afferent input reduces STT cell activity in many spinal segments. This inhibitory vagal reflex may play a role in protecting the heart.
Hobbs
S F
SF
Department of Physiology and Biophysics, University of Oklahoma Health Sciences Center, Oklahoma City 73190.
Oh
U T
UT
Chandler
M J
MJ
Foreman
R D
RD
D000005:Abdomen / Q000294:innervation; D000344:Afferent Pathways / Q000502:physiology*; D000818:Animals; D004558:Electric Stimulation; D006329:Heart Conduction System; D008251:Macaca / Q000502:physiology*; D008252:Macaca fascicularis / Q000502:physiology*; D009474:Neurons / Q000502:physiology; D013116:Spinal Cord / Q000502:physiology*; D013788:Thalamus / Q000502:physiology*; D014630:Vagus Nerve / Q000502:physiology*