Cannabinoid receptor expression and phosphorylation are differentially regulated between male and female cerebellum and brain stem after repeated stress: implication for PTSD and drug abuse.

Recent study demonstrated a close relationship between cerebellum atrophy and symptom severity of pediatric maltreatment-related posttraumatic stress disorder (PTSD). It has also been known that females are more vulnerable than males in developing anxiety disorders after exposure to traumatic stress. The mechanisms are unknown. Because cannabinoid receptors (CB₁ and CB₂) are neuroprotective and highly expressed in the cerebellum, we investigated cerebellar CB expression in stressed rats. Young male and female Sprague-Dawley rats were given 40 unpredictable electric tail-shocks for 2h daily on 3 consecutive days. CB₁ and CB₂ mRNA and protein levels in rat cerebellum and brain stem were determined using quantitative real-time PCR and Western blot, respectively. Two-way ANOVA revealed significant gender and stress effects on cerebellar CB₁ mRNA expression, with females and non-stressed rats exhibiting higher CB₁ mRNA levels than the males (3 fold, p<0.01) and stressed rats (30%, p<0.01), respectively. CB₁ and CB₂ mRNA levels in brain stem were also greater in female rats than males (p<0.01, p<0.05, respectively). Repeated stress increased the level of phosphorylated CB₁ receptors, the inactivated CB₁, in rat cerebellum (p<0.01), particularly in female rats as revealed by the significant gender × stress interaction. Thus, repeated severe stress caused greater CB₁ mRNA suppression and CB₁ receptor phosphorylation in female cerebellum that could lead to increased susceptibility to stress-related anxiety disorders including PTSD.