Increased binding of norepinephrine by nerves to cerebral blood vessels: Evidence from the effects of reserpine on nerves to cerebral and extracerebral blood vessels

It has been proposed by others that adrencrgic nerves to cerebral blood vessels bind norepinephrine more avidly than do nerves to vessels outside the brain. This suggestion is supported by the present data which show that in the rat intraperitoneal reserpine depletes norepinephrine less readily from nerves to cerebral blood vessels than from nerves to extracerebral blood vessels. Alternate hypotheses to explain our data are contradicted by available evidence, except for the hypothesis of unequal distribution of reserpine between perivascular nerves in various locations. No evidence has been located to favor the latter hypothesis. The postulate of increased norepinephrine binding by nerves to cerebral vessels not only explains the present data, but also can account for the surprisingly small responses of cerebral vessels to exogenous norepinephrine or to sympathetic stimulation.