Elucidation of the important roles played by peptides as
hypothalamic-adenohypo- physeal releasing factors, or regulatory
hormones, has in recent years led to the recognition that peptides may
also be of significance as intercellular messengers in other regions of
the nervous system. In this regard, it is interesting that Sub- stance
P, which has been proposed as a putative neurotransmitter in the spinal
cord, was rediscovered by Leeman and her co-workers during their search
for the corticotropin-releasing factor in the hypothalamus. Indeed, with
the wide- spread availability and use of radioimmunoassay techniques, it
has become ap- parent that various "hypothalamic releasing factors" are
localized in extrahypo- thalamic areas of the central nervous system as
well. This book represents an expression of the belief that the impact
on neurobiology of research into neuro- peptides will be comparable to,
if not greater than, the recent achievements obtained with the biogenic
amines. As already appears to be the case, future inves- tigations on
brain pep tides will undoubtedly uncover a host of new transmitter
candidates, with obvious implications for neuropharmacology. Perhaps the
most dramatic developments in this field have been the discoveries of
the endogenous opiate peptides (enkephalin and endorphin), and the
profound physiological and behavioral effects of specific peptides.