Effects Of Entorhinal Cortex On The Acute Stress Response

[Abstrsact] Objective: To explore the effects of the entorhinal cortex on acute stress response in rats. Materials and methods: 1.Animals:Adult male Wistar rats, weighing 250-300g, housed individually. 2. Reagents: (1) ibotenic acid and trypanblau;(2) c-Fos polyclonal antibody;(3) ABC and DAB kit. 3. Methods: All rats were grouped randomly after 7 days' feeding: control group (C), immobilization group (I), saline injection and immobilization group (EC), ibotenic injection and immobilization group (ES). Neurons in the entorhinal cortex were lesioned by bilateral injection of the cell-selective neurotoxin, ibotenic acid (1.5μg/ul of solution per side). Two weeks later, rats were subjected to immobilization stress. Expression of c-Fos in the hypothalamic paraventricular nucleus (PVN) and plasama adrenocorticotropic hormone (ACTH) after immobilization stress were observed and compared between four groups. Plasma ACTH levels were determined by radioimmunoassay, and c-Fos immunostaining was processed with the preformed avidin-biotin complex'ABC-DAB method. The data were analyzed by SPSS 13.0 for windows. Plasma ACTH concentrations was assessed by Repeated-Measures One-Way ANOVA and c-Fos by Kruskai-Wallis H. P<0.05 was considered statistically significant. Results: Rats in which ibotenic acid had been injected into the entorhinal cortex showed attenuated expression of c-Fos in the hypothalamic paraventricular nucleus (PVN) and blunted elevation of plasama adrenocorticotropic hormone (ACTH) after immobilization stress compared with rats in which saline hadbeen injected into the entorhinal cortex. Conclusions: The results of this study indicate that the entorhinal cortex is closely involved in the activation of the HPA axis during acute immobilization stress in rats.