THE SEX DIFFERENCES IN DEFENSIVE BEHAVIOR OF ADULT RATS IN RESPONSE TO EARLY NEUROINFLAMMATORY STRESS

The early proinflammatory stress induced by subcutaneous injection of the bacterial lypopolisaccaharide (LPS) on 3 and 5th postnatal days produced the changes in defensive behavior of adult rats which depended on the animal's sex. In males of the LPS group the contextual fear was more expressed after acquisition of fear conditioning and passive avoidance response while its extinction was carried out harder compared with the control groups. In females of the LPS group there were no substantial changes in expression of fear; however the extinction of the classical reflex was accelerated. The two-ways active avoidance reaction in response to the proinflammatory stress was elaborated harder and had more prolong latencies in females, and especially in males compared to the control animals. After LPS administration and repeated stresses the adult males demonstrated an increased level of IL-1 beta in the blood serum, meanwhile the females showed the high corticosterone level relative to controls. Thus, in males the early proinflammatory stress promoted the acquisition and inhibited the extinction of the passive defensive habits but made difficult acquisition of the active defensive reflexes. In total, according to the characteristics of the defensive behavior of adult animals the females were more resilient to the early proinflammatory stress than males.