G.L. Gessa

On current status of serotonin as a brain neurohormone and in action of reserpinelike drugs.

A problem of continuing interest to brain researchers is the role of serotonin in the central nervous system. The high biological activity of this aminel and its uneven distribution in brain2-4 have led a number of workers to suggest that serotonin might have a neurohumoral r ~ l e . ~ ~ Before attempting to define a precise role for brain serotonin it is worth while to examine whether it fulfills certain accepted criteria for a neurohormone. It should be stated at the outset that by neurohormone is meant either a transmitter substance or a substance that enhances or inhibits (modulates) the action of the actual transmitter?,* Although the following evidence favors the view that serotonin is a central neurohormone, it by no means adds up to rigorous proof. The most decisive type of evidence, collection and identification of the amine after stimulation, has not been obtained.

Evidence That the Rise in Temperature Produced by d-Amphetamine is Caused by a Peripheral Action of the Drug

It is not always easy to decide the extent to which certain “central” effects of drugs might be mediated peripherally or might result from interfering with a peripheral signal to the brain. We became concerned with this problem after the demonstration that the pronounced hyperactivity elicited by large doses of triiodothyronine in mice was markedly reduced by ganglionic blocking agents, such as chlorisondamine. Since amphetamine acts indirectly through the release of NE (1), we are investigating the possibility that those effect to which tolerance is readily acquired might result from a depletion of catecholamine stores at the locus of action.