Simply stated, a vasopressin receptor refers to a functional receptor located on the surface of a cell that accepts the binding of the hormone vasopressin. In mammalian physiology, this important hormone controls numerous bodily functions including permeability and blood pressure regulation. Hormones do not simply function by being in the blood stream but require specific receptors as a step of the complex process leading to actual physiological change.
A vasopressin receptor may be found in one of three main subtypes. These subtypes are AVPR1A, AVPR2, and AVPR1B, all of which are acronyms for more complex, medically termed names. The first subtype, AVPR1A, is a vasopressin receptor responsible for vasoconstriction. Vasoconstriction refers to the process of mechanically decreasing vessel circumference, resulting in an increase of blood pressure based on the physical law that area and pressure are inversely related.
The second vasopressin receptor, AVPR1B, controls specific neurological functions. Argenine vasopressin receptor 2, or AVPR2, has an antidiuretic effect on the body when stimulated by vasopressin. This basically means that it causes the body to retain water, increasing the volume of fluid within the body. If more fluid is present, then more blood is likely in the system, resulting in an increase in pressure based on volume and pressure being directly related, with vessel circumference held constant.
Using drugs, vasopressin receptors may be targeted to acquire a desired effect physiologically. Take, for example, a person who suffers from high blood pressure. High blood pressure, or hypertension, is detrimental in a number of ways and may lead to heart and vascular disease. Vasopressin increases blood pressure, so in order to reduce it, doctors may attempt to decrease the action of vasopressin in the body. As vasopressin levels are usually fairly constant, an alternative regulative measure would be to decrease the amount of receptors.
To decrease the number of functioning receptors, a pharmaceutical agent that competes with vasopressin for the receptor site is introduced into the body, for example, in pill form. If a receptor were a lock and vasopressin a key, the blood pressure drug may be thought of as an alternative key under this analogy. Each lock may only have one key in it at a time, so the alternative keys may fill enough receptors to make vasopressin less prevalent, meaning blood pressure is not as high. Analogies such as this are often utilized as a means of envisioning the abstract processes like hormone-receptor binding that serve to regulate the human body.