Dopamine-mediated behaviours produced in naive mice by bromocriptine plus SKF 38393

The ability of bromocriptine and SKF38393 (2,3,4,5-tetrahydro-7,8-dihydroxy-1-phenyl-1H-3-benzazepine) to produce some dopamine-mediated behaviours has been assessed in mice. Soon after injection, SKF38393 produced moderate increases in grooming and sniffing which were not very intense, while bromocriptine (with or without SKF38393) inhibited all grooming behaviour. Bromocriptine alone also depressed rearing and sniffing in the first hour and SKF38393 alone was without effect on rearing, but the combination produced a marked increase in the incidence of both rearing and sniffing, both of which behaviours appeared to be stereotyped. When bromocriptine-induced locomotor stimulation was peaking about 3 h after injection, as measured in automated activity cages in previous studies, there was an increase in sniffing and rearing, the incidence of which was unaffected by the addition of SKF38393, perhaps due to the shorter duration of action of SKF38393 than of bromocriptine. The data indicate that the D-1 agonist SKF38393 can qualitatively and quantitatively alter the behavioural spectrum produced by the D-2 agonist bromocriptine.