Biochemical and physiological studies of the beta-adrenoceptor and the D-2 dopamine receptor in the intermediate lobe of the rat pituitary gland: a review.

The intermediate lobe (IL) of the rat pituitary gland responds to catecholamines. Catecholamines interacting with the beta-adrenoceptor stimulate adenylate cyclase activity, enhance cyclic AMP formation and thereby trigger the release of alpha-melanocyte-stimulating hormone (alpha-MSH). Catecholamines interacting with a D-2 dopamine receptor (in the classification schema of Kebabian and Calne) diminish adenylate cyclase activity and thereby decrease the capacity of IL cells to synthesize cyclic AMP. Dopaminergic agonists also inhibit the release of alpha-MSH from IL cells. The homogeneity of the IL facilitates biochemical investigations of this tissue.