Increased grooming behaviour is induced by apomorphine in mice treated with discriminant benzamide derivatives

Grooming behaviour in mice was dose dependently increased by SK&F 38393 (1.87-30 mg/kg), whereas it was dose dependently decreased by RU 24926 (2.5-10 mg/kg) or LY 171555 (0.4-1.6 mg/kg) alone or combined with SK&F 38393 or apomorphine (0.39-6 mg/kg). The inhibitory effect of 0.75 mg/kg apomorphine on grooming behaviour was not modified by SCH 23390, chlorpromazine, clozapine and thioridazine. In contrast, it was antagonized by eight other dopamine antagonists: a partial restoration to grooming scores lower or similar to those determined in control mice was obtained with flupentixol, haloperidol, metoclopramide, thioproperazine and tiapride, whereas a reversal to grooming scores higher than those determined in control mice was obtained with mice treated with (+/-)-sulpiride, amisulpride or RIV 2093. Furthermore, only SCH 23390, chlorpromazine and clozapine antagonized SK&F 38393 (1.87 mg/kg)-induced grooming behaviour, whereas the effects of flupentixol, thioridazine, metoclopramide, haloperidol and amisulpride in SK&F 38393-treated mice were parallel to those of control mice. Finally, SCH 23390 (20 micrograms/kg) antagonized the apomorphine-induced grooming in mice treated with amisulpride, (+/-)-sulpiride or tiapride. These data confirm the potential role of D-1 dopamine receptors in the expression of grooming behaviour and indicate that the dopamine receptors involved in the inhibition of grooming could be of the D-4 subtype. Our results also reveal that chlorpromazine and clozapine have D-1 antagonist properties and suggest that the modulation of apomorphine-induced grooming behaviour by dopamine antagonists in mice could be used as a test for their classification according to their activity at the different dopamine receptor subtypes.