Activation of supraoptic magnocellular neurons by gamma 2-melanocyte stimulating hormone (gamma 2-MSH)

The effects of intracarotid infusions of the peptide gamma₂-melanocyte stimulating hormone (γ₂-MSH) on electrophysiologically and immunohistochemically identified supraoptic nucleus (SON) units were investigated Over a wide dose range this agent always excited SON units, while control infusions of vehicle had no effect. Because neural responses invariably preceded blood pressure elevation, it appears that γ₂-MSH excitation of the magnocellular system was due to a direct effect on the central nervous system and was not a result of systemic cardiovascular responses. These results suggest a forebrain γ₂-MSH sensitive site in the activation of SON magnocellular neurons.