TY - JOUR
T1 - Differential chemoreceptor reflex responses of adrenal preganglionic neurons
AU - Wei-Hua, C. A.O.
AU - Morrison, Shaun F.
PY - 2001
Y1 - 2001
N2 - Adrenal sympathetic preganglionic neurons (ADR SPNs) regulating the chromaffin cell release of epinephrine (Epi ADR SPNs) and those controlling norepinephrine (NE ADR SPNs) secretion have been distinguished on the basis of their responses to stimulation in the rostral ventrolateral medulla, to glucopenia produced by 2-deoxyglucose, and to activation of the baroreceptor reflex. In this study, we examined the effects of arterial chemoreceptor reflex activation, produced by inhalation of 100% N2 or intravenous injection of sodium cyanide, on these two groups of ADR SPNs, identified antidromically in urethane-anesthetized, artificially ventilated rats. The mean spontaneous discharge rates of 38 NE ADR SPNs and 51 Epi ADR SPNs were 4.4 ± 0.4 and 5.6 ± 0.4 spikes/s at mean arterial pressures of 98 ± 3 and 97 ± 3 mmHg, respectively. Ventilation with 100% N2 for 10 s markedly excited all NE ADR SPNs (+222 ± 23% control, n = 36). In contrast, the majority (40/48; 83%) of Epi ADR SPNs were unaffected or slightly inhibited by ventilation with 100% N2 (population response: +6 ± 10% control, n = 48). Similar results were obtained after injection of sodium cyanide. These observations suggest that the network controlling the spontaneous discharge of NE ADR SPNs is more sensitive to brief arterial chemoreceptor reflex activation than is that regulating the activity of Epi ADR SPNs. The differential responsiveness to activation of the arterial chemoreceptor reflex of the populations of ADR SPNs regulating epinephrine and norepinephrine secretion suggests that their primary excitatory inputs arise from separate populations of sympathetic premotor neurons and that a fall in arterial oxygen tension is not a major stimulus for reflex-mediated adrenal epinephrine secretion.
AB - Adrenal sympathetic preganglionic neurons (ADR SPNs) regulating the chromaffin cell release of epinephrine (Epi ADR SPNs) and those controlling norepinephrine (NE ADR SPNs) secretion have been distinguished on the basis of their responses to stimulation in the rostral ventrolateral medulla, to glucopenia produced by 2-deoxyglucose, and to activation of the baroreceptor reflex. In this study, we examined the effects of arterial chemoreceptor reflex activation, produced by inhalation of 100% N2 or intravenous injection of sodium cyanide, on these two groups of ADR SPNs, identified antidromically in urethane-anesthetized, artificially ventilated rats. The mean spontaneous discharge rates of 38 NE ADR SPNs and 51 Epi ADR SPNs were 4.4 ± 0.4 and 5.6 ± 0.4 spikes/s at mean arterial pressures of 98 ± 3 and 97 ± 3 mmHg, respectively. Ventilation with 100% N2 for 10 s markedly excited all NE ADR SPNs (+222 ± 23% control, n = 36). In contrast, the majority (40/48; 83%) of Epi ADR SPNs were unaffected or slightly inhibited by ventilation with 100% N2 (population response: +6 ± 10% control, n = 48). Similar results were obtained after injection of sodium cyanide. These observations suggest that the network controlling the spontaneous discharge of NE ADR SPNs is more sensitive to brief arterial chemoreceptor reflex activation than is that regulating the activity of Epi ADR SPNs. The differential responsiveness to activation of the arterial chemoreceptor reflex of the populations of ADR SPNs regulating epinephrine and norepinephrine secretion suggests that their primary excitatory inputs arise from separate populations of sympathetic premotor neurons and that a fall in arterial oxygen tension is not a major stimulus for reflex-mediated adrenal epinephrine secretion.
KW - Adrenal chromaffin cells
KW - Epinephrine
KW - Hypoxia
KW - Sympathoexcitation
UR - http://www.scopus.com/inward/record.url?scp=0035658732&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=0035658732&partnerID=8YFLogxK
U2 - 10.1152/ajpregu.2001.281.6.r1825
DO - 10.1152/ajpregu.2001.281.6.r1825
M3 - Article
C2 - 11705767
AN - SCOPUS:0035658732
SN - 0363-6119
VL - 281
SP - R1825-R1832
JO - American Journal of Physiology - Regulatory Integrative and Comparative Physiology
JF - American Journal of Physiology - Regulatory Integrative and Comparative Physiology
IS - 6 50-6
ER -