Tyrosine hydroxylase, but not dopamine beta-hydroxylase, is increased in rat frontal cortex after traumatic brain injury

Chronic frontal lobe functional deficits after traumatic brain injury (TBI) may be associated with altered catecholamine systems in the frontal cortex . To test this, tyrosine hydroxylase (TH) and dopamine beta-hydroxylase (DB H) levels were examined by immunohistochemistry and Western blot at 1, 7, 1 4, and 28 days after TBI or sham surgery. No alterations in DBH levels were observed by Western blot at any time point examined, but there was a signi ficant increase in TH expression 28 days after TBI (optical density 334 +/- 68% or 3.3-fold, ipsilateral and 218 +/- 39% or 2.2-fold. contralateral) r elative to the sham controls. The increase in TH may reflect a compensatory response of dopaminergic neurons to upregulate their synthesizing capacity and increase the efficiency of dopamine neurotransmission chronically afte r TBI. NeuroReport 12:2323-2327 (C) 2001 Lippincott Williams & Wilkins.