Intermediate lobe adenylate cyclase

The dopamine receptor in the intermediate lobe of the pituitary gland is negatively coupled to adenylate cyclase... 

The above-described data show that CRF added to cells of the rat Intermediate lobe In culture causes a rapid stimulation of oe-MSH release and cyclic AMP accumulation, thus demonstrating a direct action of the peptide on pars intermedia cells (15). It is however difficult, using intact cells, to dissociate between increases in cyclic AMP levels due to stimulation of adenylate cyclase activity or to Inhibition of cyclic nucleotide phosphodiesterase or to a combination of both effects. Definitive proof of the role of adenylate cyclase In the action of CRF In the intermediate lobe of the pituitary gland is provided by the following findings of a CRF-lnduced stimulation of adenylate cyclase activity in homogenate of rat and bovine pars Intermedia cells. 

In this volume a good deal of emphasis is placed on studies of dopamine receptors in pituitary. This emphasis seems well justified. The clear-cut effects of dopamine in suppressing prolactin secretion from anterior lobe mammotrophs, and the inhibitory effects on secretion of a-MSH and related secretory products from intermediate lobe are important models for dopamine receptor studies. In both cases new evidence was put forward to support the hypothesis that the actions of dopamine on the secretory cells are mediated by inhibition of adenylate cyclase. This is far easier to demonstrate in the intermediate lobe, where all cells appear to respond to dopamine, than in the anterior lobe, where the dopamine-sensitive cells probably represent only a small minority. 

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