Eighteen mongrel dogs were divided into three equal groups. Spinal cord and spinal dural blood flow in the cervical, thoracic and lumbosacral regions were measured using the radioactive microsphere technique. Measurements were taken before and 10 and 40 minutes after lumbar subarachnoid injection of one of the following: (1) physiologic saline: (2) epinephrine 200 tx 8 or (3) phenylephrine 5 rag. No significant change Or spinal cord blood flow occurred in art), of the groups, nor ~as there any

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... ifference bel~v.een the groups. Dogs receiving ,~ubaraehnoid phenylephrine did demonstrate a significanl redaction of thoracic dural blood flow at ten minutes. Dogs receiving intrathecal epinephrine or pheuylephrine demonalrated a significant reduction in lumbo-socral dural blood flow at ten minutes after injection. The reduction in dural blood flow was still evident at 40 minutes in dogs receiving phenylephriae. Subarachnoid epinephrine (200 Ixg) and phenylephrine (5 mg) do not efJect spinal cord blood flow but do produce regional dural vasoconstriction.