Interaction of ergot alkaloids with dopaminergic receptors in the rat striatum and nucleus accumbens.

Various ergot alkaloids and derivatives were investigated for their interaction with dopaminergic receptors at the level of the rat corpus striatum and nucleus accumbens. Dihydro(DH)-ergotoxine, DH-ergocornine, DH-ergocryptine, DH-ergocristine, 2-Br-alpha-ergocryptine, ergotamine and DH-ergotamine were shown to inhibit, at micromolar concentrations, the dopamine-stimulated adenylate cyclase activity of rat striatal and nucleus accumbens homogenates. Interestingly, the inhibitory effect of the ergot drugs was higher in the nucleus accumbens than in the striatum. Moreover, the ergot drugs were more active in displacing 3H-haloperidol than 3H-dopamine from striatal membranes. The results, which are in apparent contradiction with previously obtained behavioral, pharmacological and clinical data, are discussed in the light of the possible presence in the central nervous system of distinct dopaminergic receptors with different conformations.