New aspects of signal transduction in the Xenopus laevis melanotrope cell

Light and temperature stimuli act via various brain centers and neurochemical messengers on the pituitary melanotrope cells of Xenopus laevis to control distinct subcellular activities such as the biosynthesis, processing, and release of alpha-melanophore-stimulating hormone (alphaMSH). The melanotrope signal transduction involves the action of a large repertoire of neurotransmitter and neuropeptide receptors and the second messengers cAMP and Ca(2+). Here we briefly review this signaling mechanism and then present new data on two aspects of this process, viz. the presence of a stimulatory beta-adrenergic receptor acting via cAMP and the egress of cAMP from the melanotrope upon a change of alphaMSH release activity.