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Biomedical subjects

G A de Rotte

Publications and source records attributed to G A de Rotte.

4 recordsLinked to original sources
PubMed1981

Gamma-melanotropin and brain function.

In view of the close structural similarity between the pro-opiocortin fragment, gamma-MSH, and ACTH/MSH-type peptides, the behavioural profile of gamma-MSH was explored. Attention was first focused on behavioural procedures in which ACTH/MSH-related neuropeptides have been found effective. It was found that gamma-MSH and ACTH-like neuropeptides had opposite effects on avoidance behaviour. In this respect the activity of gamma-MSH resembles that of opiate antagonists rather than that of beta-endorphin. Accordingly, ACTH(1-24) induced excessive grooming which is blocked by opiate antagonists and is attenuated by gamma-MSH. In addition, gamma-MSH injected into the periaqueductal grey matter of the brainstem of opiate-naive rats elicited symptoms reminiscent of those seen after opiate withdrawal. Gamma-MSH attenuated several effects of intracerebroventricularly administered beta-endorphin (e.g. antinociception, hypothermia, alpha-MSH release) and decreased the acquisition of heroin self-administration. Although gamma-MSH at rather high doses displaced naloxone from its specific binding sites in brain homogenates, it did not interfere with beta-endorphin-induced effects on in vitro muscle preparations (guinea-pig ileum; rat rectum). Interestingly, gamma-MSH induced relaxation of the rat rectum in vitro. It is postulated that gamma-MSH may attenuate beta-endorphin-induced effects by acting via gamma-MSH receptor sites (functional antagonism), although a pharmacological antagonism cannot be excluded as yet.

Adrenocorticotropic Hormone↗
PubMed1981

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.

Adaptation, Physiological↗