Forskolin stimulates pinealocyte cGMP accumulation. Dramatic potentiation by an alpha 1-adrenergic----[Ca2+]i mechanism involving protein kinase C.

The effect of forskolin on cGMP regulation was investigated using dispersed rat pinealocytes. Forskolin stimulated cGMP accumulation in a concentration-dependent manner; this response was strongly potentiated by an alpha 1-adrenergic----[Ca2+]i mechanism involving protein kinase C. These findings provide further evidence that activation of two receptor-regulated signal transduction mechanisms may be commonly required for maximal stimulation of cGMP accumulation, and establish a new experimental approach to the study of cGMP regulation.