Neuronal Activity Within the Ventral Tegmental Area Is Correlated with Cocaine-Seeking Behavior in Male, But Not Female, Rats

The objective of this study was to begin to determine the neurobiological underpinnings of psychosocial stress-induced cocaine seeking. Social defeat stress, achieved using the well-established resident-intruder procedure, is an ecologically-valid psychosocial stressor in rodents that may more closely recapitulate those psychosocial experiences that elicit cocaine craving and relapse in human cocaine users. Our laboratory has developed a model of psychosocial stress-induced relapse in rats in which extinguished cocaine seeking is reinstated by re-exposure to a discrete cue that signals impending social defeat stress. We previously reported that an individual rat’s predilection towards the display of active coping behaviors during prior social defeat stress exposures was positively correlated with levels of psychosocial stress-induced cocaine seeking. The current study’s goal was to expand upon these initial findings by assessing and comparing patterns of neural activation within the ventral tegmental area (VTA) during stress-induced cocaine seeking triggered by psychosocial stress-predictive or foot shock stress-predictive cues. The VTA was selected for investigation in the present study because of its known role in the manifestation of stress-induced reinstatement of cocaine seeking. We postulated that neural activation in this brain region would be associated with the magnitude of observed psychosocial stress-induced cocaine seeking, thus providing important insights into the neurobiological underpinnings of this phenomenon