The cerebral surface was exposed in cats, and cerebral vasospasm was produced by subarachnoid hemorrhage (SAH) and mechanical stimulation. After four hours of repeated SAH, mechanical stimulation, and vasospasm, fluorescence histochemistry revealed a significant diminution in norepinephrine in cerebrovascular nerves ipsilateral and contralateral to the side of surgical manipulation. An identical diminution was found in nerves to mesenteric vessels of the experimental animals and in nerves to cerebral vessels of sham animals with exposed cortices, but no SAH or spasm. We conclude that the loss of norepinephrine from cerebrovascular nerves is not specifically related to SAH and mechanical stimulation of cerebral vessels, but is instead part of a more generalized adrenergic discharge produced in response to one or more undefined stimuli ("stress") present even in the sham situation.
Rosenblum WI, Guilianti D. Participation of Cerebrovascular Nerves in Generalized Sympathetic DischargeNonspecific Release of Norepinephrine in the Presence or Absence of Subarachnoid Hemorrhage and Vasospasm. Arch Neurol. 1973;29(2):91–94. doi:10.1001/archneur.1973.00490260035005