ABSTRACT
The levels of the Fos protein expression in neurons was used as an index of transcription activation in the hippocampus of common voles (Microtus arvalis Pall.) after their rapid spatial learning. Fos-positive cells were stained and calculated in 20 brain sections along hippocampal rostro-caudal axis. Voles (learning group) were trained in a modified 8-arm radial maze to find the entry to the home cage through a target arm (6 trials per session, 2-hour session). The animals were pretrained to enter the home cage through an arm isolated from the maze. Animals of active control group continued entering the home cage through the isolated arm, and animals of the passive control group were taken for the Fos immunohistochemistry from the home cage. Both in the learning group and active control group, a significant increase in c-Fos expression was shown in all the examined areas (CA1, CA3 and the dentate gyrus) as compared to the passive control. A significant increase in the number of c-Fos positive neurons was observed in the caudal hippocampus of the learning animals as compared to the active control, however, no differences were found in the rostral part. The maximum effects were observed in the dentate gyrus and the CA3 field. The results suggest a functional rostro-caudal inhomogeneity of the vole's hippocampus in the spatial learning task.
