Background: Recent studies suggest that long-term exposure to stress can sensitize animals to subsequent novel or acute stressors. Stressors affect amygdala activity, and the prefrontal cortex has been implicated in the regulation of responses to stress. Little is known, however, about how the physiology of amygdala neurons is altered by chronic stressors or the role of the prefrontal cortex in these changes.
Methods: We used in vivo extracellular recordings from neurons in the rat central and basolateral amygdala nuclei to examine the effects of chronic stress on the basal firing and responses of amygdala neurons to a novel stressor. Additionally, prefrontal cortical afferents were severed to examine its role in the modulation of the response to stressors.
Results: Chronic exposure to cold enhanced the sensitivity of central amygdala neurons to footshock. A portion of this may be due to enhanced basolateral amygdala output. Furthermore, prefrontal cortical regulation of this response is weakened by chronic stress.
Conclusions: The physiology of the amygdala is altered by chronic stress. Furthermore, the prefrontal cortical regulation of these responses may be weakened after chronic stress. This is a potential biological substrate for abnormal affect upon chronic stress and its effect on affective disorders.