Changes of rat cerebellar guanosine 3',5'-cyclic phosphate by dopaminergic mechanisms in vivo.

Apomorphine produced a dose-dependent increase of the cGMP level in the cerebellum. Haloperidol and scopolamine completely prevented this increase, and reserpine reduced the increase to 50%. LSD elevated cerebellar cGMP, and this effect was also abolished by haloperidol. It is suggested that the primary site of action of these drugs is the caudate nucleus, from which two neuronal pathways could trigger the increase of cGMP in the cerebellum.