This study examined the relationship between
papaverine-sensitive and -insensitive components of vasospasm, arterial contractility and compliance, and time after
subarachnoid hemorrhage (SAH) in dogs. Eighteen dogs underwent angiography and then two intracisternal
injections of blood. Angiography was repeated 4 (n = 5), 7 (n = 4), 10 (n = 4), or 14 (n = 5) days later.
Papaverine, 100 to 200 mg, was infused into the basilar artery, and angiography was repeated. Four additional dogs had cerebral angiography only and served as controls. The basilar arteries were removed and studied pharmacologically. Significant vasospasm of the basilar artery was observed each time after SAH.
Papaverine significantly reversed vasospasm at 4 and 7 days (88 +/- 6% and 63 +/- 11% of vasospasm reversed; analysis of variance, P < 0.05). The
papaverine-insensitive component of vasospasm increased significantly with increasing time after SAH and with increasing severity of vasospasm. Arterial contractility and compliance decreased significantly with increasing time after SAH and were significantly related to the degree of
papaverine-insensitive vasospasm but not to the severity of vasospasm. In conclusion, the majority of vasospasm early after SAH in dogs was caused by reversible vasoconstriction. The ability of
papaverine to reverse vasospasm depended on the time after SAH and on the severity of vasospasm, a finding that may be important to the use of
papaverine in humans. The pathological and biochemical basis for the association between
papaverine-insensitive vasospasm and reduced arterial wall contractility and compliance remains to be determined.