The influence of repeated treatment with imipramine, (+)- and (-)-oxaprotiline on behavioural effects of dopamine D-1 and D-2 agonists.

The paper examined the action of imipramine, (+)- and (-)-oxaprotiline, administered repeatedly to rats, on the behavioural effects of the dopamine D-1 and D-2 agonists, SKF 38393 and quinpirole, respectively. The three antidepressants studied, given in the single dose or repeatedly, attenuate the enhanced grooming evoked by SKF 38393. The locomotor hyperactivity, evoked by quinpirole administered s.c., is increased by repeated but not single-dose treatment with imipramine and (+)-oxaprotiline [but not with (-)-oxaprotiline]. Quinpirole at a low dose produces the locomotor hypoactivity which is attenuated by repeated, but not single-dose, treatment with the anti-depressants studied here. Repeated imipramine and (+)-oxaprotiline [but not (-)-oxaprotiline] increase the locomotor activity effect of quinpirole injected into the nucleus accumbens. The results indicate that the enhanced responsiveness of the dopamine system, observed previously after repeated treatment with antidepressants, may be mediated by the dopamine D-2 receptors.