Blockade of apomorphine-induced yawning in rats by the dopamine autoreceptor antagonist (+)-AJ 76.
The effects of the putative, selective dopamine autoreceptor antagonist (+)-AJ 76 on yawning, penile grooming and mouth movements induced by small doses of apomorphine in male rats were examined. Yawning induced by 0.05mg/kg apomorphine was dose dependently blocked by (+)-AJ-76, significant decreases being observed at 0.86 and 3.5mg/kg of the drug. A dose of 0.86mg/kg (+)-AJ 76 caused a two fold shift to the right of the apomorphine dose response curve for yawning. In contrast, (+)-AJ 76 had no effect on penile grooming and vacuous mouth movements induced by small doses of apomorphine. This pattern of results is similar to that observed after bilateral 6-hydroxydopamine-induced lesions of the substantia nigra which also blocked apomorphine-induced yawning but spared penile grooming and mouth movements. Previous studies have suggested that (+)-AJ 76 is a selective dopamine autoreceptor antagonist that has little or no effect on behaviour mediated by post-synaptic dopamine receptors. Therefore, these data provide further support for the hypothesis that apomorphine-induced yawning is mediated by dopamine autoreceptors.
Dourish
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Merck Sharp and Dohme Research Laboratories, Neuroscience Research Centre, Harlow, Essex, U.K.
Herbert
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Iversen
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D000818:Animals; D001058:Apomorphine / Q000037:antagonists & inhibitors*; D001522:Behavior, Animal / Q000187:drug effects; D008297:Male; D009281:Naphthalenes / Q000494:pharmacology*; D051381:Rats; D011919:Rats, Inbred Strains; D011954:Receptors, Dopamine / Q000187:drug effects* / Q000502:physiology; D013764:Tetrahydronaphthalenes / Q000494:pharmacology*; D015000:Yawning / Q000187:drug effects* / Q000502:physiology
D009281:Naphthalenes; D011954:Receptors, Dopamine; D013764:Tetrahydronaphthalenes; C051171:5-methoxy-1-methyl-2-(n-propylamino)tetralin; D001058:Apomorphine