AJP - Regulatory, Integrative and Comparative Physiology, Vol 249, Issue 1 91-R99, Copyright © 1985 by American Physiological Society
Spinal pathways mediating respiratory influences on sympathetic nerves
C. A. Connelly and R. D. Wurster
The location of spinal pathways mediating the respiratory modulation of
sympathetic nerve activity was determined. Left inferior cardiac
sympathetic, phrenic, and external intercostal (T1) nerve activities were
recorded in 16 alpha-chloralose-anesthetized, vagotomized, paralyzed cats.
Baroreceptor reflex activation of sympathetic activity was tested by
bilateral carotid occlusion. Eight cats received C6-C7 level ventral spinal
cord hemisections followed by cumulative lesions leading to total spinal
cord transection. Eight other cats received C6-C7 level dorsolateral
funiculus (DLF) lesions followed by dorsal spinal cord hemisection and
subsequent spinal cord transection. The respiratory modulation of
sympathetic activity was quantitatively assessed using
respiration-triggered computer summation of sympathetic activity. Ventral
hemisection had no significant effect on the respiratory modulation of
sympathetic activity or bilateral carotid occlusion responses. In contrast,
bilateral DLF lesions eliminated both the respiratory modulation and
bilateral carotid occlusion responses. Unilateral disruption of DLF
pathways ipsilateral to the recorded sympathetic nerve indicated spinal
level decussations. Thus bilaterally descending DLF pathways with spinal
level decussations mediate the respiratory modulation of sympathetic
activity.
