A Study On The Changes Of Acetylcholine Receptors After Brain Concussion In Rats

Objective: To observe the changes of Ml, M2 and N acetylcholine receptors following brain concussion(BC) in rats and research the neurobiology mechanisms of cognitive behavioral deficits after BC. Methods: The brain concussion was induced by a metallic pendulum-striker concussive device in rats. Animals subjected BC were randomized into six injured groups (the group of 1d, 2d, 4d, 8d, 16d, 24d post-concussive injury, n=8). Additionally, 8 intact rats served as one control. The Ml, M2 and N acetylcholine receptors expression in PFC CA1~4, thalamus CPU VDB and MSN were studied by using the immunohistochemistry (streptavidin-peroxidase , S-P) method and image analyze system. Results: 1. The Ml receptor expression in CA1-4 thalamus, PFC, VDB, CPU and MSN declined comparing with the control after BC and began to recover in different time. By the 24d, receptor expression has had been close to or lower than the control. The Ml receptor expression in thalamus decreased significantly (P<0.05) at 1d, 4d and 16d. 2. The M2 receptor expression in CA1-4 and thalamus declined after injured and subsequently began to recover, but in some areas was lower comparing with the control at 24d. The M2 receptor expression in thalamus decreased significantly (P<0.05) at 1d, 8d and 24d. The M2 receptor expression in PFC, VDB, CPU and MSN instantly increased after injured and then rapidly decreased, however it is slight lower comparing with the control at 24d. 3. The N receptor expression in CA1-4 , thalamus, PFC, VDB and CPU failed after injured and recovered in different time in different area. It remained lower expression until 24d. The N receptorexpression in PFC decreased significantly, 1d comparing with 16d (P<0.05). The decrease in MSN after injury is inconspicuous. Conclusions: 1. The model of brain concussion in rats can be established successfully using a metallic pendulum-strike concussive device. 2. The Ml, M2 and N acetylcholine receptors may distribute in neurons of every cerebral layer hippocampus thalamus CPU MSN basal forebrain and ependyma cell. 3. The expression of Ml, M2 and N acetylcholine receptors in PFC CA1~4 thalamus CPU VDB and MSN had some changeable tendency after BC. 4. The changes of acetylcholine receptor in related brain region were possibly involved in cognitive behavioral deficits in BC rats.