Activation of mu-opioid receptors in rat ventrolateral medulla selectively blocks baroreceptor reflexes while activation of delta opioid receptors blocks somato-sympathetic reflexes

T. Miyawaki, A. K. Goodchild, P. M. Pilowsky

Research output: Contribution to journalArticle

52 Citations (Scopus)

Abstract

The effects of activation of mu and delta-opioid receptors in the rostral ventrolateral medulla (RVLM) on somato-sympathetic, baroreceptor and chemoreceptor reflexes, as well as respiratory rhythmicity in sympathetic nerves, were examined in urethane anaesthetized (1.1-1.2 g/kg) and artificially ventilated Sprague-Dawley rats. Microinjection of the delta-opioid receptor agonist [D-Pen2,5]-enkephalin (DPDPE; 8 mM, 50 nl) bilaterally into the RVLM potently inhibited the post-inspiratory-related burst discharges of lumbar sympathetic nerve activity (LSNA) but had only limited effects on splanchnic sympathetic nerve activity (SSNA) and phrenic nerve discharge. Injection of DPDPE into the RVLM strongly attenuated the somato-sympathetic reflex (∼ 50-80%) evoked in the lumbar sympathetic nerve and splanchnic sympathetic nerve by tibial nerve stimulation but had no effect on baroreceptor reflexes and chemoreceptor reflexes evoked by aortic nerve stimulation and brief hypoxia, respectively. Injection of the mu-opioid receptor agonist, [D-Ala2N-Me-Phe4, Gly-ol5]-enkephalin (DAMGO; 4 mM, 50 nl), also elicited a greater inhibition of LSNA than SSNA accompanied by an abolition of phrenic nerve discharge. Injection of DAMGO inhibited the baroreceptor reflex without significant effect on either the somato-sympathetic or the chemoreceptor reflexes. We propose that opioid peptides diminish specific excitatory and inhibitory inputs to the presympathetic neurons in RVLM via distinct presynaptic receptor subclasses.

Original languageEnglish
Pages (from-to)133-144
Number of pages12
JournalNeuroscience
Volume109
Issue number1
DOIs
Publication statusPublished - 18 Jan 2002
Externally publishedYes

Fingerprint Dive into the research topics of 'Activation of mu-opioid receptors in rat ventrolateral medulla selectively blocks baroreceptor reflexes while activation of delta opioid receptors blocks somato-sympathetic reflexes'. Together they form a unique fingerprint.

Cite this