Cranial Irradiation Altered Dendritic Spine Complexity in the Rat Hippocampus and Induced Memory Decline

Abstract

Cognitive deficit was the most serious complication of cranial irradiation. However, the underlying mechanisms remain obscure. Dendrites are the anatomic bases of synaptic contact and action potential propagation. Alterations of dendritic architecture may contribute to radiation-induced memory dysfunction. 21-day-old Sprague-Dawley rats received 10Gy cranial irradiation. 1 and 3 months later, Morris Water Maze, Fear Conditioning test and novel object recognition were used to test the memory function. Golgi staining was used to assess changes in dendritic spine density and morphology. Moreover, cytoskeletal proteins PSD-95 were analyzed with Western blot. Our data showed that 10Gy cranial irradiation induced significant decline in the spatial memory and memory retention of rats and accompanied the morphological changes in dendritic spines. The result revealed significant reductions in spine density at 1 month (40.58%) and 3 months (28.92%) in the DG. In CA1 basal dendrites, irradiation resulted in a significant reduction (33.29%) in spine density only at 1month postirradiation. Compared to control, mushroom spines reduced at 1 month (7.17%, 10.01%) and 3 months (9.29%, 11.94%) post irradiation in DG and CA1 basal dendrites, respectively. Also, we found PSD-95 depletion coincided in time with alteration in dendritic spines. These data suggest that cranial irradiation decreased the dendritic spine density and mushroom spines, which may be associated with radiation-induced memory dysfunction. Acknowledgment: This study was supported by the National Natural Science Foundation of China 81402517 and the Suzhou Science and Technology Project SYS201651.