Pharmacological investigations on adaptation in rats subjected to cold water immersion stress

The present study was designed to investigate whether adaptogenic factors may be transferred from stress adapted rats to naïve rats and to explore the nature of endogenous adaptogens by pharmacological modulation. The rats were subjected to cold water immersion stress by placing them individually in a tank of water (depth=15.5cm; temperature=16±2°C) for 5min. The rats were subjected to single episode of cold water immersion stress for acute stress; while for adaptation, the rats were subjected to repeated episodes of same stressor for 5 consecutive days. The plasma of stress adapted rats was administered to naïve rats before subjecting to acute stress. The stress related behavioral alterations were assessed using the actophotometer, the hole board, the open field and the social interaction tests. Acute stress with single episode of cold water immersion was associated with behavioral alterations. However, the behavioral alterations were significantly restored on subjecting repeated episodes of cold water immersion. Administration of plasma of stress adapted rats also attenuated acute stress associated behavioral alterations. Administration of naltrexone abolished the restoration of behavioral changes as a part of adaptive process in repeated stress subjected rats as well as the anti-stress effects of plasma of stress adapted rat. It may be concluded that opioids may be the potential endogenous adaptogens that tend to restore the homeostasis during repeated episodes of stress. Furthermore, the endogenous adaptogens may be transferred in the form of plasma from repeated stress subjected rats to the naïve rats to confer the anti-stress properties.