TY - JOUR
T1 - Inhibition of chemoreceptor inputs to nucleus of tractus solitarius neurons during baroreceptor stimulation
AU - Mifflin, S. W.
PY - 1993
Y1 - 1993
N2 - The reflex effects of arterial chemoreceptor activation are attenuated as arterial pressure is elevated and augmented as arterial pressure is decreased. This study was designed to test the hypothesis that excitatory arterial chemoreceptor inputs to neurons in the nucleus tractus solitarius (NTS) are inhibited by arterial baroreceptors. In pentobarbital sodium- anesthetized, mechanically ventilated, paralyzed cats, extracellular recordings were obtained from NTS neurons, which were excited after brief activation of ipsilateral carotid body chemoreceptors. During increases in arterial pressure, carotid sinus nerve (CSN)-evoked discharge was 45-112% of the control-evoked discharge at the prevailing level of arterial pressure (n = 70). Inhibition of CSN-evoked discharge during increased arterial pressure was significant when evoked discharge was <90% of control (n = 31; 67 ± 2%, mean percent of control-evoked discharge ± SE; P < 0.01, Wilcoxon signed- rank test). The inhibition of CSN-evoked discharge was reduced after section of both vagi, both aortic nerves, and the contralateral CSN (n = 5, P < 0.05). These results demonstrate that activation of arterial baroreceptors attenuates excitatory chemoreceptor inputs to a subpopulation of NTS neurons. The inhibition appears to be mediated by disfacilitation. The results indicate that baroreceptor modulation of arterial chemoreflexes occurs at an early stage of the reflex arc, within the NTS. The results also suggest that sympathoinhibition evoked by baroreceptors might include, as a component, reduced sympathoexcitatory, i.e., chemoreceptor, drive.
AB - The reflex effects of arterial chemoreceptor activation are attenuated as arterial pressure is elevated and augmented as arterial pressure is decreased. This study was designed to test the hypothesis that excitatory arterial chemoreceptor inputs to neurons in the nucleus tractus solitarius (NTS) are inhibited by arterial baroreceptors. In pentobarbital sodium- anesthetized, mechanically ventilated, paralyzed cats, extracellular recordings were obtained from NTS neurons, which were excited after brief activation of ipsilateral carotid body chemoreceptors. During increases in arterial pressure, carotid sinus nerve (CSN)-evoked discharge was 45-112% of the control-evoked discharge at the prevailing level of arterial pressure (n = 70). Inhibition of CSN-evoked discharge during increased arterial pressure was significant when evoked discharge was <90% of control (n = 31; 67 ± 2%, mean percent of control-evoked discharge ± SE; P < 0.01, Wilcoxon signed- rank test). The inhibition of CSN-evoked discharge was reduced after section of both vagi, both aortic nerves, and the contralateral CSN (n = 5, P < 0.05). These results demonstrate that activation of arterial baroreceptors attenuates excitatory chemoreceptor inputs to a subpopulation of NTS neurons. The inhibition appears to be mediated by disfacilitation. The results indicate that baroreceptor modulation of arterial chemoreflexes occurs at an early stage of the reflex arc, within the NTS. The results also suggest that sympathoinhibition evoked by baroreceptors might include, as a component, reduced sympathoexcitatory, i.e., chemoreceptor, drive.
KW - arterial baroreflex
KW - arterial chemoreflex
KW - central cardiovascular regulation
KW - central nervous system
KW - central respiratory regulation
UR - http://www.scopus.com/inward/record.url?scp=0027178892&partnerID=8YFLogxK
U2 - 10.1152/ajpregu.1993.265.1.r14
DO - 10.1152/ajpregu.1993.265.1.r14
M3 - Article
C2 - 8342679
AN - SCOPUS:0027178892
VL - 265
SP - R14-R20
JO - American Journal of Physiology - Regulatory Integrative and Comparative Physiology
JF - American Journal of Physiology - Regulatory Integrative and Comparative Physiology
SN - 0363-6119
IS - 1 34-1
ER -