Behavioral and biochemical evidence of apomorphine-induced supersensitivity of the striatal dopamine receptors.
The effect of repeated administration of apomorphine was studied behaviorally and biochemically in rats bearing either a unilateral lesion of the substantia nigra with 6-OHDA or an electrolytic lesion of the entopeduncular nucleus. Rats with the nigral lesion displayed a progressive increase in contralateral circling rate. In animals with the entopeduncular lesion, the ipsiversive circling response was unchanged after the eight injection of apomorphine. [3H] Spiroperidol binding to striatal membranes did not appear modified by the apomorphine treatment on the intact side. It was however increased on the side of the 6-OHDA lesion. We propose that a denervated striatum responds to repeated stimulation by dopamine agonists with a paradoxical increase in sensitivity. This may explain in part the appearance of dyskinesia in treated parkinsonian patients.
D000818:Animals; D001058:Apomorphine / Q000494:pharmacology*; D003342:Corpus Striatum / Q000187:drug effects*; D005260:Female; D008566:Membranes / Q000378:metabolism; D008636:Mesencephalon / Q000502:physiology; D009068:Movement / Q000187:drug effects*; D051381:Rats; D011919:Rats, Inbred Strains; D011954:Receptors, Dopamine / Q000187:drug effects*; D013134:Spiperone / Q000378:metabolism; D013378:Substantia Nigra / Q000502:physiology
D011954:Receptors, Dopamine; D013134:Spiperone; D001058:Apomorphine