Neuropeptides in cardiovascular control.
Neuropeptides can affect cardiovascular function in various ways. They can serve as cotransmitters in the autonomic nervous system; for example, vasoactive intestinal peptide (VIP) is released with acetylcholine and neuropeptide Y with norepinephrine from postganglionic neurons. Substance P and, presumably, other peptides can can affect cardiovascular function when released near blood vessels by antidromically conducted impulses in branches of stimulated sensory neurons. In the central nervous system, many different neuropeptides appear to function as transmitters or contransmittes in the neural pathways that regulate the cardiovascular system. In addition neuropeptides such as vasopressin and angiotensin II also circulate as hormones that are involved in cardiovascular control. Large doses of exogenous vasopressin are required to increase blood pressure in normal animals because the increase in total peripheral resistance produced by the hormones is accompanied by a decrease in cardiac output. However, studies with synthetic peptides that selectively antagonize the vasopressor action of vasopressin indicate that circulating vasopressin is important in maintaining blood pressure when animals are hypovolemic due to dehydration, haemorrhage or adrenocortical insufficiency. VIP dilates blood vessels and stimulates renin secretion by a direct action on the juxtaglomerular cells. Renin secretion is stimulated when the concentration of VIP in plasma exceeds 75 pmol/litre, and higher values are seen in a number of conditions. Neostigmine, a drug which increases the secretion of endogenous VIP, also increases renin secretion, and this increase is not blocked by renal denervation or propranolol. Thus, VIP may be a physiologically significant renin stimulating hormone.(ABSTRACT TRUNCATED AT 250 WORDS)
D000818:Animals; D001921:Brain / Q000187:drug effects / Q000502:physiology; D002320:Cardiovascular Physiological Phenomena; D002319:Cardiovascular System / Q000187:drug effects; D004285:Dogs; D009419:Nerve Tissue Proteins / Q000494:pharmacology / Q000502:physiology*; D051381:Rats; D012084:Renin-Angiotensin System / Q000187:drug effects; D014660:Vasoactive Intestinal Peptide / Q000494:pharmacology / Q000502:physiology; D014667:Vasopressins / Q000494:pharmacology / Q000502:physiology
D009419:Nerve Tissue Proteins; D014667:Vasopressins; D014660:Vasoactive Intestinal Peptide