Forskolin stimulates the conversion of tyrosine to dopamine in catecholaminergic neural tissue

Forskolin stimulates the conversion of tyrosine to dopamine in slices and synaptosomes from rat striatum, in synaptosomes from rat hypothalamus, and in slices from bovine retina. In striatal synaptosomes, there is an approximately 80% stimulation of dopamine formation from tyrosine, but no effect with DOPA as substrate, suggesting that the effect is on tyrosine hydroxylase. Stimulation is saturable with a half-maximal effect at under 1 microM forskolin. Forskolin stimulation is additive with, and hence independent of , activation due to KCl, but not that due to dibutyryl-cyclic AMP. Stimulation of dopamine synthesis by forskolin may provide an approach for elucidating the regulation of the adenylate cyclase system associated with catecholaminergic nerve endings.