Increased norepinephrine synthesis in the cerebral hemispheres of rats following subarachnoid hemorrhage.

Norepinephrine (NE) was assayed in rat brains 72 h after the creation of an experimental subarachnoid hemorrhage (SAH). NE in the cerebral hemispheres was found to increase by 64% when compared to controls. NE in the brainstem and cerebellum was unchanged. The kinetics of hemispheric NE metabolism were then studied in control and SAH rats. SAH caused a 3-fold increase in NE synthesis and a 44% reduction in turnover time when compared to controls. These results may reflect increased activity of central noradrenergic neuronal pathways in SAH.