Impairment by apomorphine of one-trial passive avoidance learning in mice: the opposing roles of the dopamine and noradrenaline systems.
Pretraining administration of the dopaminergic stimulant apomorphine (0.25--16 mg/kg) impaired retention performance of mice on a one-trial passive avoidance task. Only with a very high dose (16 mg/kg) of this drug did the effect seem related to an interference with memory formation processes. Of the dopamine receptor-blocking agents used, haloperidol (0.125--1 mg/kg), but not chlorpromazine or clozapine (0.25--4 mg/kg), prevented the apomorphine effect. Phenoxybenzamine (8 mg/kg), a noradrenaline receptor-blocker, antagonized the haloperidol effect and, when combined with a subeffective dose of apomorphine, impaired passive avoidance learning. The results obtained are interpreted in terms of the proposed inhibitory actions exerted by central noradrenaline on dopamine systems of the brain.
D000818:Animals; D014150:Antipsychotic Agents / Q000494:pharmacology; D001058:Apomorphine / Q000494:pharmacology*; D001362:Avoidance Learning / Q000187:drug effects*; D004298:Dopamine / Q000502:physiology*; D004347:Drug Interactions; D008297:Male; D051379:Mice; D008813:Mice, Inbred ICR; D009638:Norepinephrine / Q000502:physiology*; D010643:Phenoxybenzamine / Q000494:pharmacology
D014150:Antipsychotic Agents; D010643:Phenoxybenzamine; D001058:Apomorphine; D004298:Dopamine; D009638:Norepinephrine