Central amygdaloid involvement in neuroendocrine correlates of conditioned stress responses

The purpose of this study was to examine the effects of bilateral electrolytic lesions of the central nucleus of the amygdala (CEA) in comparison with sham lesions on neuroendocrine responses during conditioned emotional stress in male Wistar rats. Lesions in the CEA, made either before or after the single learning trial of inescapable footshock, failed to affect the conditioned response of plasma epinephrine levels. Plasma levels of norepinephrine showed neither a conditioned stress effect nor were influenced by lesioning. Pre-training CEA lesions, but not post-training intervention, abolished the conditioned elevations of circulating plasma corticosterone and prolactin. These results suggest that the CEA is involved in the conditioning rather than the retention of neuroendocrine stress responses. The effects of pre-training lesioning of the CEA can possibly be explained by a reduced feedback of all these neuroendocrine factors during or shortly after acquisition. In addition, there is a remarkable differentiation between various hormonal correlates of conditioned stress following CEA lesioning. Only corticosterone and prolactin, that appear to be correlates of a passive behavioural stress response, were abolished. The lesions failed to affect the sympatho-active stress parameters (epinephrine and norepinephrine). Relations between coping strategy-active and passive behaviour-and physiology in connection with CEA functioning are discussed.