NPY and related substances.

NPY exhibits a broad distribution throughout the body. NPY has been localized in neurons that synthesize norepinephrine or epinephrine and also in many cell bodies which are not catecholaminergic. Coexistence of NPY and several other peptides has also been observed. Accordingly, NPY displays a wide variety of functional activities depending on its location and coexistence with other substances, especially catecholamines. NPY exerts direct effects at several targets and also modulates the cellular response to catecholamines and to peptides such as LHRH. It is reasonable to expect that NPY will modulate the pre- and postjunctional effects of catecholamines at many of their targets in view of the distribution of NPY in central catecholaminergic neurons and throughout the preaortic and sympathetic chain ganglia. Virtually nothing is known at the time of this writing about NPY receptors and postreceptor transduction mechanisms at different sites of NPY activity. Equally mysterious are the pre- and postjunctional receptor-coupled transduction mechanisms which are involved in the modulation of catecholaminergic or other peptidergic effects by NPY. The distribution of NPY and its involvement in cardiovascular, GI, endocrine, and neuroendocrine systems suggest that NPY may be an extremely important regulator of a spectrum of physiological functions.