Effects and interactions between alpha-MSH and MCH/NEI upon striatal cAMP levels.

It is known that alpha-MSH augments cAMP levels in rat brain slices containing accumbens and caudate-putamen nuclei. In this study we examined: a) the effect of other neuropeptides: MCH and NEI, on this cyclic nucleotide; b) if the effects of alpha-MSH on cAMP production can be modulated by addition of MCH or NEI to the incubation medium. Both MCH and NEI (3.6 microM) increased the production of cAMP, whereas at doses of 0.6 microM exerted no effects. When alpha-MSH 0.6 microM was added with NEI or MCH (0.6 microM), only MCH blocked the increase in the cAMP induced by alpha-MSH. Neither MCH nor NEI at the highest dose used (3.6 microM) had any additive effect on AMPc when added together with alpha-MSH. We conclude that, at a high concentration, (MCH/NEI)-like peptides can use the intracellular signal transduction linked to cyclic nucleotides in the CNS.