title: Dopamine agonist-induced locomotor activity in rats treated with 6-hydroxydopamine at differing ages: functional supersensitivity of D-1 dopamine receptors in neonatally lesioned rats.
abstract: Locomotor responses caused by dopamine receptor agonists with presumed specificity for D-1 or D-2 receptor subtypes were compared to apomorphine-induced locomotion in neonatally and adult 6-hydroxydopamine (6-OHDA)-treated rats. In adult 6-OHDA-treated rats, apomorphine and the D-2 agonist, LY-171555, produced a marked, dose-related increase in locomotor activity. Increases in locomotion observed in neonatally 6-OHDA-treated rats after apomorphine and LY-171555 administration were less than one-third of those seen in rats treated as adults with 6-OHDA. Neonatally 6-OHDA-treated rats, positive for L-dihydroxyphenylalanine-induced self-biting, exhibited a small increase in locomotion after a single exposure to SKF-38393, a D-1 dopamine agonist. Subsequent administration of SKF-38393 to these rats resulted in an additional elevation of the locomotor response which reached a maximum after four doses. Adult 6-OHDA-treated rats were less sensitive to the locomotor stimulant effects of SKF-38393 than were neonatally 6-OHDA-treated rats. SKF-38393 and LY-171555 produced several behaviors in neonatally 6-OHDA-treated rats that were similar. These results indicate that D-1 dopamine receptors contribute to modulation of central dopaminergic function. Haloperidol and cis-flupentixol antagonized apomorphine-induced locomotion comparably in control and adult 6-OHDA-treated rats. The D-1 dopamine receptor antagonist, SCH-23390, was a less effective blocker of apomorphine-induced locomotion in 6-OHDA-treated rats than in controls. Therefore, the ability of SCH-23390 to attenuate apomorphine in control rats is likely dependent upon intact catecholamine-containing neurons.(ABSTRACT TRUNCATED AT 250 WORDS)
mesh_terms: D015647:2,3,4,5-Tetrahydro-7,8-dihydroxy-1-phenyl-1H-3-benzazepine; D000367:Age Factors; D000818:Animals; D000831:Animals, Newborn; D001058:Apomorphine / Q000494:pharmacology; D001552:Benzazepines / Q000494:pharmacology; D018492:Dopamine Antagonists; D004305:Dose-Response Relationship, Drug; D004873:Ergolines / Q000494:pharmacology; D005260:Female; D005475:Flupenthixol / Q000494:pharmacology; D006220:Haloperidol / Q000494:pharmacology; D006892:Hydroxydopamines / Q000633:toxicity*; D008297:Male; D009043:Motor Activity / Q000187:drug effects*; D016627:Oxidopamine; D011247:Pregnancy; D019257:Quinpirole; D051381:Rats; D011919:Rats, Inbred Strains; D011954:Receptors, Dopamine / Q000187:drug effects*
chemical_list: D001552:Benzazepines; D018492:Dopamine Antagonists; D004873:Ergolines; D006892:Hydroxydopamines; D011954:Receptors, Dopamine; D019257:Quinpirole; D015647:2,3,4,5-Tetrahydro-7,8-dihydroxy-1-phenyl-1H-3-benzazepine; D016627:Oxidopamine; D005475:Flupenthixol; D006220:Haloperidol; D001058:Apomorphine