Effects of the dopamine D-1 antagonist SCH 23390 on water intake, water-rewarded operant responding and apomorphine-induced decrease of water intake in rats.
The specific dopamine (DA) D-1 receptor antagonist SCH 23390 was found to attenuate operant lever-pressing with water as reward in a dose-dependent manner and more potently than drinking itself. This effect occurred in the same fashion as previously reported for DA D-2 antagonists. In contrast to the DA D-2 antagonist haloperidol, the attenuated operant lever-pressing induced by the DA D-1 antagonist SCH 23390 was not counteracted by the anticholinergic drug scopolamine. The decreased water intake in thirsty animals caused by a low dose of apomorphine was not antagonised by SCH 23390. This has previously been found with DA D-2 antagonists, such as haloperidol and sulpiride. The results show that in spite of some similarities in the behavioural effects of DA D-1 and D-2 antagonists, a closer pharmacological analysis is able to reveal pronounced differences.
Ljungberg
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Department of Pharmacology, Karolinska Institute, Stockholm, Sweden.
D000818:Animals; D001058:Apomorphine / Q000494:pharmacology*; D001552:Benzazepines / Q000494:pharmacology*; D003216:Conditioning, Operant / Q000187:drug effects*; D018492:Dopamine Antagonists; D004305:Dose-Response Relationship, Drug; D004327:Drinking Behavior / Q000187:drug effects*; D004347:Drug Interactions; D008297:Male; D051381:Rats; D011919:Rats, Inbred Strains; D012601:Scopolamine / Q000494:pharmacology; D014868:Water Deprivation / Q000502:physiology
D001552:Benzazepines; D018492:Dopamine Antagonists; D012601:Scopolamine; D001058:Apomorphine