AJP - Heart and Circulatory Physiology, Vol 232, Issue 5 464-H469, Copyright © 1977 by American Physiological Society
Autonomic afferents at T1 in elicitation of volume-induced tachycardia in the dog
P. D. Gupta and M. Singh
Intravenous infusion of blood elicited tachycardia in anesthetized dogs
with beta-receptor blockade (dogs with vagal efferents intact but cardiac
sympathetic efferents blocked) and bradycardia in dogs with combined
beta-receptor blockade and rhizotomy at T1 (dogs with vagal efferents
intact but cardiac sympathetic efferents plus autonomic afferents at T1
blocked). This suggests that tachycardia elicited by volume in infusion may
be partly due to a reflex with its afferent pathway at the T1 segment of
the spinal cord and its efferent pathway in the vagi. Moreover, infusion
evoked bradycardia in dogs with right-sided rhizotomy at T1, which was not
significantly different from the response elicited in dogs with bilateral
rhizotomy at T1. Additionally, the tachycardia response induced in dogs
with ventral or dorsal rhizotomy at T1 was significantly different from the
bradycardia response elicited in dogs with both dorsal and ventral
rhizotomy at T1. These results suggest that the afferent pathway
predominates on the right side, and its entry at T1 may be via both dorsal
and ventral roots.
