Pharmacological characterization of the receptors involved in the apomorphine-induced polyphasic modifications of locomotor activity in mice.
Increasing doses of apomorphine elicited polyphasic changes in locomotor activity in mice, consisting of: (i) hypokinesia with a peak effect at 25 micrograms/kg, which was not antagonized by various neuroleptics used at the highest doses not changing spontaneous locomotor activity, except for haloperidol; (ii) a relative restoration of locomotor activity at 75 micrograms/kg; this effect was antagonized by all the neuroleptics tested (except clozapine) and was hardly affected by domperidone and sulpiride; this apomorphine-induced effect was markedly increased 12 days after ICV 6-hydroxydopamine, (iii) a further hypokinetic effect with a peak effect at 150 micrograms/kg-1 (occurring simultaneously with hypothermia) which was antagonized by all the neuroleptics tested (including sulpiride at low doses) except levomepromazine and clozapine, and was again hardly affected by domperidone; this hypokinesia was reduced after prior (24 h) administration of 5 mg/kg apomorphine, (iv) finally another restoration of locomotor activity was observed at doses of apomorphine above 200 micrograms/kg.
D000818:Animals; D014150:Antipsychotic Agents / Q000494:pharmacology; D001058:Apomorphine / Q000494:pharmacology*; D001831:Body Temperature / Q000187:drug effects; D004347:Drug Interactions; D006892:Hydroxydopamines / Q000494:pharmacology; D007276:Injections, Intraventricular; D008297:Male; D051379:Mice; D009043:Motor Activity / Q000187:drug effects*; D016627:Oxidopamine; D011954:Receptors, Dopamine / Q000187:drug effects*
D014150:Antipsychotic Agents; D006892:Hydroxydopamines; D011954:Receptors, Dopamine; D016627:Oxidopamine; D001058:Apomorphine