Effects Of Entorhinal Cortex On Different Types Of The Stress Response

Objective:In our previous study, a lesion in the entorhinal cortex was found to sig-nificantly attenuate the elevation of c-Fos in hypothalamic paraventricular nucleus (PVN) during restraint stress. The aim of this study is to investigate the effects of the entorhinal cortex on acute multiple stress and psychological stress and study the dif-ferent effects on c-Fos in PVN between those two types of stress. Materials andMethods:1. Animals:Adult male Sprague-Dawley rats (280±20g) were purchased from Zhejiang Academy of Medical Sciences and housed in group of five.2. Reagents:①ibotenic acid and trypanblau;②c-Fos polyclonal antibody;③ABC and DAB kit.3. Methods:All rats were grouped randomly after seven day’s feeding:control group (N), foot-shock group (F), saline injection and foot-shock group (FC), ibotenic injection and foot-shock group (FS), restraint group (R), saline injection and restraint group (RC), ibotenic injection and restraint group (RS). Neurons in the entorhinal cortex were lesioned by bilateral injection of the cell-selective neurotoxin, ibotenic acid (0.2μl15μg/μl of solution per side). Two weeks later, rats were subjected to acute unavoid-able foot-shock stress and restraint stress. We examined the expression of the immedi-ate-early gene c-fos in the PVN in rats in response to foot-shock stimulation and re-straint stress. c-Fos immunostaining was processed with the preformed avidin-biotin complex ABC-DAB method. The data were analyzed by SPSS16.0for windows. c-Fos was assessed by Kruskai-Wallis H. P<0.05was considered statistically signifi-cant. Results:(1) Rats in which ibotenic acid had been injected into the entorhinal cortex showed attenuated expression of c-Fos in PVN after acute foot-shock and re-straint stress compared with rats in which saline had been injected into the entorhinal cortex;(2) There were no significant difference of c-Fos expression between the two types of stress. Conclusions:(1) The results indicats that the entorhinal cortex is closely involved in the activiation of the HPA during acute multiple stress and acute psychological stress in rats. According to the two results, we hypothesized that the en-torhinal cortex at least participates in some aspects of information processing of abso-lute malignant stimulus;(2) The c-Fos expression induced by different types of stimu-lus maybe relate with the controllability of stress;(3) According to our previous re-search, one conclusion can be drawn that the entorhinal cortex is related to both physi-ological and psychological stress.