Clinical and experimental observations indicate that the larger cerebral arteries in man are capable of vasoconstriction when subjected to certain types of artificially imposed mechanical stimuli. Vasodilatation can be induced by topical application of 2% procaine or 3% papaverine after dissection or test stimuli have caused vasospasm. Observations indicate that the basal cerebral arteries react to trauma as do other arteries of the body. This response to trauma appears to be the same whether the stimulus is mechanical during an experiment or is the result of a disease process, such as rupture of an aneurysm, perivascular hemorrhage, or, perhaps, other pathological conditions.
Pool JL, Jacobson S, Fletcher TA. CEREBRAL VASOSPASM-CLINICAL AND EXPERIMENTAL EVIDENCE. JAMA. 1958;167(13):1599-1601. doi:10.1001/jama.1958.02990300025005