Effect of etorphine on adrenergic neurotransmission in the rat and guinea pig heart.
The effect of etorphine (ET) on nerve stimulation-mediated release of norepinephrine (NE) was investigated in isolated rat and guinea pig hearts. Hearts were perfused with Krebs bicarbonate solution via the aorta and the overflow of NE was measured after stimulation of the heart. ET (0.001-0.1 mumol/l) caused a dose-dependent inhibition of NE release in both preparations. Inhibition of NE release from guinea pig hearts ranged from 13% at 0.001 mumol/l to 24% at 0.1 mumol/l. The same concentrations of ET decreased NE release by 10 and 36% in the rat heart. The inhibitory effect of ET was blocked by naloxone. It is concluded that presynaptic opioid receptors located on the adrenergic neuronal terminals may be involved in the regulation of adrenergic neurotransmission in the rat and guinea pig heart.
Semafuko
W E
WE
Department of Pharmacology and Toxicology, School of Pharmacy, University of Kansas, Lawrence.
Follett
D L
DL
Dixon
W R
WR
D000818:Animals; D004558:Electric Stimulation; D005048:Etorphine / Q000494:pharmacology*; D006168:Guinea Pigs; D006321:Heart / Q000294:innervation*; D066298:In Vitro Techniques; D008297:Male; D009019:Morphinans / Q000494:pharmacology*; D009206:Myocardium / Q000378:metabolism; D009270:Naloxone / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains; D013564:Sympathetic Nervous System / Q000187:drug effects*; D009435:Synaptic Transmission / Q000187:drug effects*
D009019:Morphinans; D009270:Naloxone; D005048:Etorphine