Melanocyte-stimulating hormone and adaptive behaviour

In order to study the physiological role of alpha-MSH in adaptive behaviour, plasma concentrations of alpha-MSH were measured during acquisition and extinction of active avoidance behaviour and during retention of a passive avoidance response. In addition the effect on behaviour of neutralization of centrally available alpha-MSH by intracerebroventricular administration of antisera to alpha-MSH was investigated. Blood samples were collected either before or immediately after each acquisition session and also before and after the extinction session of an active avoidance response. In addition, blood was collected after retention of a passive avoidance response from rats which had been submitted t different shock intensities during the learning trial, resulting in various passive avoidance groups of animals could be found. Neutralization or reduction of available alpha-MSH in the brain by intracerebroventricular administration of antisera to this neuropeptide results in disturbances in active as well as passive avoidance behaviour. This may indicate that alpha-MSH available in the brain plays a physiological role in brain functions involved in adaptive behaviour and in processes related to learning. Thus, at least in some species, MSH manifests its adaptive function predominantly via the brain.