MSH/ACTH4-10 influences on the CAR in human subjects: a negative finding

Abba Kastin: The melanocyte stimulating hormone story and the future of the proteophathies

From a personal viewpoint, Abba was always a congenial colleague and a good friend. I recall the hours of unraveling complex, confusing, and many times contradictory data sets with him and the excitement we both felt as what had been puzzling began to make sense. Most of all, I feel privileged to have Abba as a long and valued friend.

Concepts for biologically active peptides

Here we review a unique aspect of CNS research on biologically active peptides that started against a background of prevalent dogmas but ended by exerting considerable influence on the field. During the course of refuting some doctrines, we introduced several concepts that were unconventional and paradigm-shifting at the time. We showed that (1) hypothalamic peptides can act 'up' on the brain as well as 'down' on the pituitary, (2) peripheral peptides can affect the brain, (3) peptides can cross the blood-brain barrier, (4) the actions of peptides can persist longer than their half-lives in blood, (5) perinatal administration of peptides can exert actions persisting into adulthood, (6) a single peptide can have more than one action, (7) dose-response relationships of peptides need not be linear, (8) the brain produces antiopiate as well as opiate peptides, (9) there is a selective high affinity endogenous peptide ligand for the mu-opiate receptor, (10) a peptide's name does not restrict its effects, and (11) astrocytes assume an active role in response to metabolic disturbance and hyperleptinemia. The evolving questions in our laboratories reflect the diligent effort of the neuropeptide community to identify the roles of peptides in the CNS. The next decade is expected to see greater progress in the following areas: (a) interactions of peptides with other molecules in the CNS; (b) peptide involvement in cell-cell interactions; and (c) peptides in neuropsychiatric, autoimmune, and neurodegenerative diseases. The development of peptidomics and gene silencing approaches will expedite the formation of many new concepts in a new era.

MSH/ACTH4-10 and task-induced increase in tendon reflexes and heart rate

Earlier studies revealed that during a binary choice reaction task an increase of tendon reflex amplitudes and heart rate can be found, together with a suppression of heart rate variability. The results were interpreted as a task-induced increase in generalized arousal. In this study two experiments, consisting of a rest period and a binary choice reaction task, were done. In Experiment 1, twenty subjects, in a cross-over design, received 15 mg MSH/ACTH4-10 or a placebo. Only reflexes were recorded. In experiment 2, three groups of 9 subjects received either 30 or 15 mg MSH/ACTH4-10 or a placebo. Reflexes, heart rate and heart rate variability were recorded. Rest-task differences of reflexes and heart rate were enhanced by the drug. We hypothesized that MSH/ACTH4-10 intensified the arousal effect of the task.

Enkephalin and other peptides reduce passiveness

Enkephalin and other brain peptides previously have been shown to be active in the dopa potentiation test which may be considered an animal model of mental depression. A recently described model of passive immobility during swimming, also sensitive to tricyclic antidepressants, was therefore used to study a large number of naturally occurring peptides and some of their analogues. It was found that several enkephalins with no opiate activity after peripheral injection reduced the immobility and thus increased the activity of swimming rats. alpha-MSH, but not its 4--10 core or a 4--9 analogue, also caused significantly more swimming than did the diluent control. As we have previously found in several animal and clinical studies, a smaller dose of MIF-I was more effective than larger doses. The results confirm our concept of the CNS actions of brain peptides and support the suggestion that some of them, like the enkephalins, might be useful after peripheral administration in mental depression or other CNS disorders.