The effects of quipazine, fenfluramine and apomorphine on the morphine potentiation of tonic immobility.
Acute administration of morphine (2 mg/kg, IM) enhanced tonic immobility (TI) durations in three-week old chickens. This effect could be reversed with the 5-HT receptor agonist quipazine. Similarly, promoting 5-HT release by fenfluramine antagonized the morphine potentiation of the response. Both 5-HT agonists reduced TI durations. Finally, the DA receptor agonist apomorphine produced decrements in TI duration and blocked the effect of morphine. The results suggest the involvement of serotonergic and dopaminergic mechanism in the morphine potentiation of the response. The findings are also discussed in terms of a revised serotonergic model of tonic immobility.
D000818:Animals; D001058:Apomorphine / Q000494:pharmacology*; D001921:Brain / Q000187:drug effects; D002645:Chickens; D004357:Drug Synergism; D005277:Fenfluramine / Q000494:pharmacology*; D009020:Morphine / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D009043:Motor Activity / Q000187:drug effects*; D011954:Receptors, Dopamine / Q000187:drug effects; D011985:Receptors, Serotonin / Q000187:drug effects
D011954:Receptors, Dopamine; D011985:Receptors, Serotonin; D005277:Fenfluramine; D009020:Morphine; D001058:Apomorphine