The effect of alpha-adrenergic innervation on caudate blood flow.

A thermal diffusion probe, with cannulas for intracerebral microinfusion of drugs and an electrode to monitor electroencephalographic (EEG) activity, was used to examine the local effect of vasoactive amines in a 4 to 5 mm sphere of caudate nucleus in cats. The results demonstrated that it is possible to alter local cerebral blood flow (CBF) without causing any change in systemic blood pressure or heart rate, or in CBF and the EEG in the opposite caudate. One-microliter intracerebral injections, containing varying amounts of phenylephrine, increased local CBF in proportion to dose. The effect was blocked by intracerebral infusion of phentolamine. However, local alpha-adrenergic blockade did not inhibit vascular responses to blood pressure elevation or to metabolic influences on local blood flow.