Faculty Collaboration Database

The effects of morphine on sympathetic transmission in the stellate ganglion of the cat. Can J Physiol Pharmacol 1986 Jul;64(7):940-6

Date

07/01/1986

Pubmed ID

3021308

DOI

10.1139/y86-162

Scopus ID

2-s2.0-0022549123 (requires institutional sign-in at Scopus site)   13 Citations

Abstract

The aim of this study was to investigate which of the processes involved in synaptic transmission are affected by morphine in concentrations comparable to those used during surgical procedures. The effects of morphine sulfate on ganglionic transmission were studied in the stellate ganglion of the cat using intracellular and extracellular recordings in vitro. The neurons of the stellate ganglion were depolarized using preganglionic nerve stimulation, postganglionic nerve stimulation, and intracellular stimulation before and after introduction of morphine sulfate (up to 20 micrograms/mL). Tissue concentrations of morphine were estimated using radiolabeled morphine. Axonal transmission and the excitability of the postganglionic neurons to direct intracellular stimulation was not affected at the concentrations of morphine studied. In addition, morphine had a dose-dependent depolarizing effect on the resting membrane potential of most of the neurons in the stellate ganglion. Such neuronal depolarizations alone could initially produce excitation in some cell populations, followed by inhibition, secondary to the membrane depolarization, leading to depression of sympathetic nerve activity. The overall ganglionic transmission as recorded using an evoked potential was biphasic. At low doses morphine facilitated transmission, while at larger doses morphine attenuated evoked potentials. These effects do not appear to be mediated through classical opiate receptors since they are not blocked by naloxone.

Author List

Bosnjak ZJ, Seagard JL, Roerig DL, Kostreva DR, Kampine JP

Author

Zeljko Bosnjak PhD, MS Emeritus Professor in the Medicine department at Medical College of Wisconsin

MESH terms used to index this publication - Major topics in bold

Animals
Cats
Evoked Potentials
Female
Male
Membrane Potentials
Morphine
Neural Conduction
Stellate Ganglion
Synaptic Transmission