Neurogenic Control of Cerebral Circulation

A review of recent literature provides evidence that cerebral vessels are innervated with myelinated and nonmyelinated nerves. Among the latter, adrenergic nerves are readily demonstrated. Stimulation of cervical sympathetics produces a reduction in cerebral blood flow attributable to constriction of vessels in the neck and on the cerebral surface. In vitro experiments indicate that cerebral vessels possess a mechanism responsive to sympathomimetic agents. Evidence indicates that neurogenic influences can alter cerebrovascular diameter without necessarily playing a role in maintaining resting tone. Data are also available which suggest that neurogenic influences may modulate the response of cerebral vessels to other more potent stimuli. Cerebral vessels are less sensitive and less responsive to neurogenic influences than are vessels elsewhere. However, available data suggest that this characteristic of the cerebral vasculature reflects specialization of vascular muscle or of perivascular nerves, rather than a vestigial basis for the existence of these nerves.