Dopamine receptor
Dopamine receptor D1 and Dopamine receptor D5 are Gs coupled receptors that stimulate adenylyl cyclase to produce cAMP, increasing intracellular calcium among other cAMP mediated processes. The D2 class of receptors produce the opposite effect, as they are Gαi coupled receptors, and block the activity of adenylyl cyclase. cAMP mediated protein kinase A activity also results in the phosphorylation of DARPP-32, an inhibitor of protein phosphatase 1. Sustained D1 receptor activity is kept in check by Cyclin-dependent kinase 5. Dopamine receptor activation of Ca2+/calmodulin-dependent protein kinase II can be cAMP dependent or independent.