Here we examined how the levels of catecholamine neurotransmitter regulatory proteins VMAT2, COMT, MAO are altered to explain the increased dopamine and norepinephrine levels seen in the pre-frontal cortex (PFC) following traumatic brain injury (TBI).

TBI often occurs as an impact to the head and can cause lasting impairments of cognitive processes that lead to increased risk-taking behavior in clinical populations. The laboratory has recently demonstrated that female, but not male, rats increase preference for risky choices after multiple injuries. Our goal is to understand the underlying neural mechanisms that drive TBI-induced increases in risk-taking behavior.

Groups of age-matched adult male and female Long Evans rats (n=6-8 per group) received either an experimental traumatic brain injury using closed head control cortical impact (CH-CCI) or were in the sham surgery group. Rats were sacrificed and brain tissue from the sub-regions of the PFC (mPFC, OFC, and ACC) were collected and standard western blotting protocols were used to measure the levels of VMAT2, COMT, and MAO in each brain region.

We observed there were no overall differences in protein levels across all three specific regions of the PFC using one-way ANOVAs (p > 0.05). However, multiple comparisons revealed multiple injury-induced alterations of protein levels in the OFC region only. There were decreases observed in VMAT2 and COMT levels indicating less packaging of catecholamine neurotransmitters and a possible secondary compensatory mechanism response to lowered catecholamine levels. Interestingly, MAO-A was increased in males, but decreased in females following injury which may underlie the sex specific differences previously observed.

Based upon these findings in the study, we concluded that there are changes in the levels of catecholamine neurotransmitter regulatory proteins and further studies will pinpoint how these sex differential changes maybe regulating sex-specific preference for risky choice following head injury.