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This study shows the possible contribution of muscarinic receptors in the pathophysiology of post-traumatic stress disorder. Sprague-Dawley rats of both sexes were exposed to dirty cat litter (trauma) for 10 min and the protocol was repeated 1 week later with a trauma reminder (clean litter). The rats also received intraperitoneal fluoxetine (2.5, 5 or 10 mg/kg/day), propranolol (10 mg/kg/day) or saline for 7 days between two exposure sessions. Functional behavioral experiments were performed using elevated plus maze, following exposure to trauma reminder. Western blot analyses for M(1), M(2), M(3), M(4) and M(5) receptor proteins were employed in the homogenates of the hippocampus, the frontal cortex and the amygdaloid complex. The anxiety indices increased from 0.63±0.02 to 0.89±0.04 in rats exposed to the trauma reminder. The freezing times were also recorded as 47±6 and 133±12 s, in control and test animals respectively. Fluoxetine or propranolol treatments restored the increases in the anxiety indices and the freezing times. Female rats had higher anxiety indices compared to males. Western blot data showed increases in M(2) and M(5) expression in the frontal cortex. Expression of M(1) receptors increased and M(4) subtype decreased in the hippocampus. In the amygdaloid complex of rats, we also detected a down-regulation of M(4) receptors. Fluoxetine and propranolol only corrected the changes occurred in the frontal cortex. These results may imply that muscarinic receptors are involved in this experimental model of post-traumatic stress disorder., (Copyright © 2012 Elsevier B.V. All rights reserved.)

We compared different stress conditions on brain BDNF levels, in rats exposed to social isolation test (SIT) and predator scent tests (PST). BDNF expression in the frontal cortex, hippocampus, and amygdala was compared, and effects of chronic fluoxetine (FLU) treatment were evaluated. Rats were exposed to SIT and PST for one month. FLU was given (5 mg/kg/day, ip) throughout stress procedures. Controls, stress, and treatment groups were evaluated in elevated plus maze, anxiety scores were calculated. BDNF expression was determined by Western blot. SIT and PST induced anxiety in both sexes, females had greater anxiety scores than males (p<0.05). FLU restored anxiety scores in both sexes (p<0.01) in both tests. Male and female rats exhibited reduced cortical BDNF levels in SIT (p<0.001). PST reduced cortical BDNF in females, but increased in males. Hippocampal BDNF expression was lowered in SIT (p<0.01) and PST (p<0.001) in both sexes. Female rats had 40% lower BDNF expression than males in the amygdala in SIT. FLU did not restore cortical BDNF in females in both tests, but reduced increased BDNF levels in males in PST (p<0.001). FLU did not restore reduced brain BDNF in males in the hippocampus and amygdala, but restored in hippocampus, in females. Our findings indicate that sex differences must be considered in studies related to mood disorders of animal models, and suggest that BDNF expression in different brain regions are altered differentially in a gender-dependent manner in rats. Antianxiety effect of FLU is not mediated through increasing BDNF activity in cortex in both genders. Increased BDNF in hippocampus and amygdala may reflect antidepressant effect of FLU in female rats, but not in males. [ABSTRACT FROM AUTHOR]