Development of acute tolerance during exposure of hippocampal explants to an opioid peptide.
Bath application of FK 33-824, a stable enkephalin analogue, altered synaptic potentials and induced sustained depolarization shifts in hippocampal pyramidal cells. In a proportion of cells, these excitatory effects diminished and then disappeared within 6-8 min during FK 33-824 perfusion. This desensitization was temperature-sensitive. In contrast, no desensitization to similar excitatory effects of bicuculline was seen after acute application. This GABA-antagonist also excited cells which first had been rendered tolerant to the action of FK 33-824, but cross-tolerance occurred between FK 33-824 and (D-Ala)2-(D-Leu)5-enkephalin.
D000818:Animals; D005405:D-Ala(2),MePhe(4),Met(0)-ol-enkephalin; D004305:Dose-Response Relationship, Drug; D004361:Drug Tolerance; D004723:Endorphins / Q000494:pharmacology*; D004745:Enkephalins / Q000494:pharmacology*; D005071:Evoked Potentials / Q000187:drug effects; D006624:Hippocampus / Q000187:drug effects*; D009474:Neurons / Q000187:drug effects; D051381:Rats; D011957:Receptors, Opioid / Q000187:drug effects*
D004723:Endorphins; D004745:Enkephalins; D011957:Receptors, Opioid; D005405:D-Ala(2),MePhe(4),Met(0)-ol-enkephalin