Bromocriptine and lisuride stimulate the accumulation of cyclic AMP in intact slices but not in homogenates of rat neostriatum

The effects of bromocriptine and lisuride on cyclic AMP concentrations in homogenates and in intact slices of rat neostriatum were investigated. Significant increases in cyclic AMP concentration were found after a 10-min exposure to bromocriptine and lisuride in striatal intact slices. On the contrary, as previously found, the two dopaminergic ergot derivatives did not stimulate dopamine-sensitive adenylate cyclase present in striatal homogenates. The stimulatory effects observed only in intact tissues were blocked by the specific dopamine receptor blocking agent fluphenazine. It is tempting to conclude that dopaminergic ergot derivatives have a site of action different from that stimulated by classic dopamine agonists in tissue homogenates.