AUTHOR=Xing Guoqiang , Carlton Janis , Jiang Xiaolong , Wen Jillian , Jia Min , Li He 

TITLE=Differential Expression of Brain Cannabinoid Receptors between Repeatedly Stressed Males and Females may Play a Role in Age and Gender-Related Difference in Traumatic Brain Injury: Implications from Animal Studies

JOURNAL=Frontiers in Neurology

VOLUME=5

YEAR=2014

URL=https://www.frontiersin.org/journals/neurology/articles/10.3389/fneur.2014.00161

DOI=10.3389/fneur.2014.00161

ISSN=1664-2295

ABSTRACT=<p>Inconsistent gender differences in the outcome of TBI have been reported. The mechanism is unknown. In a recent male animal study, repeated stress followed by TBI had synergistic effects on brain gene expression and caused greater behavioral deficits. Because females are more likely to develop anxiety after stress and because anxiety is mediated by cannabinoid receptors (CBRs) (CB<sub>1</sub> and CB<sub>2</sub>), there is a need to compare CB<sub>1</sub> and CB<sub>2</sub> expression in stressed males and females. CB<sub>1</sub> and CB<sub>2</sub> mRNA expression was determined in the amygdala, hippocampus, prefrontal cortex (PFC), and hypothalamus of adolescent male and female rats after 3 days of repeated tail-shock stress using qPCR. PFC CB<sub>1</sub> and CB<sub>2</sub> protein levels were determined using Western blot techniques. Both gender and stress had significant effects on brain CB<sub>1</sub> mRNA expression levels. Overall, females showed significantly higher CB<sub>1</sub> and CB<sub>2</sub> mRNA levels in all brain regions than males (<italic>p</italic> &lt; 0.01). Repeated stress reduced CB<sub>1</sub> mRNA levels in the amygdala, hippocampus, and PFC (<italic>p</italic> &lt; 0.01, each). A gender × stress interaction was found in CB<sub>1</sub> mRNA level in the hippocampus (<italic>p</italic> &lt; 0.05), hypothalamus (<italic>p</italic> &lt; 0.01), and PFC (<italic>p</italic> &lt; 0.01). Within-sex one-way ANOVA analysis showed decreased CB<sub>1</sub> mRNA in the hippocampus, hypothalamus, and PFC of stressed females (<italic>p</italic> &lt; 0.01, each) but increased CB<sub>1</sub> mRNA levels in the hypothalamus of stressed males (<italic>p</italic> &lt; 01). There was a gender and stress interaction in prefrontal CB<sub>1</sub> receptor protein levels (<italic>p</italic> &lt; 0.05), which were decreased in stressed females only (<italic>p</italic> &lt; 0.05). Prefrontal CB<sub>2</sub> protein levels were decreased in both male and female animals after repeated stress (<italic>p</italic> &lt; 0.05, each). High basal levels of CBR expression in young naïve females could protect against TBI damage whereas stress-induced CBR deficits could predict a poor outcome of TBI in repeatedly stressed females. Further animal studies could help evaluate this possibility.</p>