title: Effects of morphine, ethylketocyclazocine, and N-allylnormetazocine on classical conditioning of the rabbit nictitating membrane response.
abstract: The rabbit's nictitating membrane response was classically conditioned to tone and light conditioned stimuli presented for 800 ms before delivery of a 100-ms unconditioned shock stimulus. Both the mu receptor agonist morphine (5 mg/kg) and the kappa receptor agonist ethylketocyclazocine (1 mg/kg) significantly retarded the acquisition of conditioned responses (CRs). The retardant effects of both morphine and ethylketocyclazocine on CR acquisition could still be detected when the rabbits were tested 5 days after cessation of drug injections. At the dose employed in this study (5 mg/kg), the sigma receptor agonist N-allylnormetazocine had no effect on acquisition. The retardant effects of morphine and ethylketocyclazocine on acquisition were significantly antagonized by both naloxone (1 mg/kg) and N-allylnormetazocine (5 mg/kg). It was suggested that mu and possibly kappa receptors are involved in the retardant effects of opiates on the acquisition of classically conditioned responses.
mesh_terms: D000818:Animals; D003214:Conditioning, Classical / Q000187:drug effects*; D003215:Conditioning, Eyelid / Q000187:drug effects*; D003496:Cyclazocine / Q000031:analogs & derivatives* / Q000494:pharmacology; D016314:Ethylketocyclazocine; D005260:Female; D008027:Light; D008297:Male; D009020:Morphine / Q000494:pharmacology*; D009541:Nictitating Membrane; D010620:Phenazocine / Q000031:analogs & derivatives* / Q000494:pharmacology; D011817:Rabbits; D013016:Sound
chemical_list: D016314:Ethylketocyclazocine; C012134:SK&F 10047; D009020:Morphine; D010620:Phenazocine; D003496:Cyclazocine