Peptidergic control of cardiovascular function: The angiotensin paradigm

If we consider the chemical messengers in the central nervous system, there are about ten classic transmitters--the catecholamines, biogenic amines and amino acids--as opposed to over 50 different neuropeptides. These include previously well-established circulating hormones such as angiotensin, atrial natriuretic peptide, vasopressin and oxytocin, calcitonin and calcitonin gene related peptide (CGRP), the opioid family of peptides, gastrointestinal peptides, pituitary peptides and their releasing factors, and miscellaneous peptides such as the kinins, bombesin, gallanin, and others; all occur as neuropeptides in the brain. There is evidence supporting a role in central cardiovascular control for angiotensin, opioid peptides, substance P, neuropeptide Y, vasopressin, atrial natriuretic peptide, kinins, corticotropin releasing factor, bombesin, somatostatin, and some other peptides. They have been localized in brain areas known to be important for blood pressure regulation, and specific high-affinity peptide receptors have also been discovered. Upon central administration, these peptides produce cardiovascular effects, partly by interacting with other blood pressure-controlling neuroregulators, e.g. catecholamines and GABA. Central inhibition of brain peptide synthesis or interaction with competitive antagonists at the receptor site results in marked cardiovascular effects. Altered peptide levels and activity of synthesizing enzymes, as well as supersensitivity to the pressor action of some brain peptides, have been described in experimental models of hypertension. We are using angiotensin as a model peptide to study the peptidergic control of cardiovascular function.