Accepted_test

The stress response is a universal response of the body to various changes in the external environment and includes many components, among which are nonspecific components and specific changes in the expression of a number of genes, including early genes such as egr1, fos, npas4, and others. In the first series of our experiment, Wistar rats were subjected to unavoidable swimming stress in a cylinder for the Porsolt test for 15 min. In the second series, Wistar rats were daily (4 days) subjected to swimming stress for 5 min. On the fifth day, some animals were subjected to swimming for 15 min as in the first series. In the first series after acute swimming, we found an increase in the expression of fos and npas4 genes in both hippocampal parts and egr1 only in the ventral hippocampus. Scopolamine suppressed stress-induced increase in the expression of npas4 and egr1 but not fos gene. In the second series of experiments, stress caused by swimming on the fifth day also induced an increase in fos expression in both hippocampal parts and an increase in egr1 expression in the ventral hippocampus. Scopolamine did not affect fos expression after stress; and has no effect on egr1 expression in the ventral hippocampus. The acute unavoidable stress induces expression of early genes in both dorsal and ventral hippocampi; however, inhibition of the muscarinic receptors suppressed stress-induced changes in the gene expression only in the case of presentation of novel stress context.