Ergometrine and its biphasic action at dopaminergic receptors in the nucleus accumbens of rats.

Bilateral administration of ergometrine into the nucleus accumbens of rats pretreated 40 min earlier with apomorphine (0.9 mg/kg, s.c.) resulted in a shift from a predominant licking score to a predominant gnawing score. Bilateral administration of ergometrine or (3.4-dihydroxyphenylamino)-2-imidazoline into the brain of rats treated 20 min later with apomorphine (2.0 mg/kg, s.c.) resulted in a shift from a predominant licking and gnawing score to a predominant walking and sniffing score. These and related data suggest a biphasic action at a certain group of dopamine receptors within the nucleus accumbens of rats: a short-term activation and along-term inhibition following this initial activation. The predictive value of the behavioural profile triggered by ergometrine for the evaluation of antidepressant effects of centrally acting drugs is discussed.