The effect of enkephalins and of beta-endorphin on the hypertensive response to physostigmine in the rat.
1 Intracarotid injection of [Leu]enkephalin and [Met]enkephalin produced a dose-dependent biphasic change in blood pressure of the rat consisting of an initial shortlasting fall followed by a longlasting increase of blood pressure. Naloxone consistently depressed or abolished the effects of enkephalins on blood pressure. 2 Intracarotid injection of beta-endorphin only occasionally produced a hypotension, or did not produce any change in the blood pressure of the rat. 3 All three opioids ([Leu]enkephalin, [Met]enkephalin and beta-endorphin) significantly depressed or abolished the hypertensive response to intravenous injection of physostigmine. This depressive action of opioids was easily reversed by naloxone. 5 It is concluded that opioids depress the central cholinergic link implicated in the hypertensive response to physostigmine most probably by inhibiting acetylcholine and/or noradrenaline release in the structures relevant for the action of physostigmine on blood pressure of the rat. This interaction is realized through the activation of opioid receptor(s).
D000818:Animals; D001794:Blood Pressure / Q000187:drug effects*; D002395:Catecholamines / Q000494:pharmacology; D004743:Enkephalin, Leucine / Q000494:pharmacology; D004744:Enkephalin, Methionine / Q000494:pharmacology; D004745:Enkephalins / Q000494:pharmacology*; D005260:Female; D008297:Male; D009270:Naloxone / Q000494:pharmacology; D010830:Physostigmine / Q000494:pharmacology*; D051381:Rats; D011919:Rats, Inbred Strains; D001615:beta-Endorphin / Q000494:pharmacology*
D002395:Catecholamines; D004745:Enkephalins; D009270:Naloxone; D004744:Enkephalin, Methionine; D004743:Enkephalin, Leucine; D001615:beta-Endorphin; D010830:Physostigmine