Distinct neural representations and cognitive behaviors attributable to naturally-developed active avoidance or reactive escape strategies in the male rat.

BACKGROUND: The high individual variability in coping with stress is often attributed to either genetic background differences, sustained environmental conditions, or a combination of both. However, the neural mechanisms underlying coping style variability are yet poorly understood.

METHODS: Here we examined the impact of a single extended emotional challenge on coping style variability, and the associated involvement of the hippocampus, medial prefrontal cortex (mPFC) and periaqueductal gray (PAG). Male Sprague-Dawley rats (n = 170) were trained in an extended two-way shuttle avoidance (eTWSA) task for 7 days, and daily avoidance rates were measured. Forced swim test, elevated plus maze or Morris water maze were tested before or after eTWSA exposure. Excitotoxic lesion of the hippocampal dentate gyrus (DG) was performed by Ibotenic infusion. Transient pharmacological blocking of DG, mPFC or PAG was performed by muscimol or CNQX+TTX infusion.

RESULTS: Exposing rats to eTWSA was found to lead to naturally-developing dichotomous, not continuous, coping styles, we termed 'active avoidance (AA)' or 'reactive escape (RE)'. Prior emotional responses did not predict the developing coping style. AA was associated with beneficial outcomes including reduced behavioral despair and improved spatial learning. RE led to impaired spatial retrieval. AA was abolished by lesioning or pharmacological blocking of the DG. RE was prevented by blocking mPFC or PAG.

CONCLUSION: The results indicate that a single exposure to a significant emotional challenge can lead, in otherwise healthy individuals, to dichotomous development of an active or reactive coping style, with distinctive neural correlates and subsequently behavioral significance.