Differential chemoreceptor reflex responses of adrenal preganglionic neurons

Wei Hua Cao, Shaun Morrison

Research output: Contribution to journalArticle

16 Citations (Scopus)

Abstract

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.

Original languageEnglish (US)
JournalAmerican Journal of Physiology
Volume281
Issue number6 PART 2
StatePublished - Dec 2001
Externally publishedYes

Fingerprint

Reflex
Neurons
Sodium Cyanide
Epinephrine
Ventilation
Norepinephrine
Arterial Pressure
Population
Chromaffin Cells
Baroreflex
Urethane
Deoxyglucose
Intravenous Injections
Inhalation
Oxygen
Injections

Keywords

  • Adrenal chromaffin cells
  • Epinephrine
  • Hypoxia sympathoexcitation

ASJC Scopus subject areas

  • Physiology (medical)

Cite this

Differential chemoreceptor reflex responses of adrenal preganglionic neurons. / Cao, Wei Hua; Morrison, Shaun.

In: American Journal of Physiology, Vol. 281, No. 6 PART 2, 12.2001.

Research output: Contribution to journalArticle

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abstract = "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.",
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