Sex differences and chronic stress effects on the neural circuitry underlying fear conditioning and extinction
Section snippets
Chronic stress, psychopathology, and corticolimbic structure and function
Women are more susceptible than men to stress-related mental illness and twice as likely to experience depression [1], [2]. There is also a greater incidence of most types of anxiety disorders, such as social anxiety, phobias, and posttraumatic stress disorder (PTSD), among women compared to men [3]. However, after women experience menopause, a stage of life marked by a pronounced decline in ovarian hormones, this sex difference diminishes [4], [5]. In women, depression is also more likely to
Chronic stress effects on neuronal morphology
As in primates, prefrontal cortex in rodents can be subdivided into several major subregions. Medial prefrontal cortex includes anterior cingulate, prelimbic, and infralimbic cortex. This region is functionally homologous to the primate dorsolateral and ventromedial prefrontal cortices, and plays a role in autonomic and HPA axis regulation, emotion regulation [e.g., prelimbic cortex plays a role in expression of conditioned fear, while infralimbic cortex plays a role in retrieval of extinction,
Sex differences in dendritic morphology
In rats, medial prefrontal cortex is sexually dimorphic. For instance, intact, unstressed females had smaller and less complex apical dendritic arbors in prelimbic cortex pyramidal neurons than intact, unstressed males [69], [98], [99] (see Fig. 2). Given that medial prefrontal cortex contains estrogen and progesterone receptors [100], this sexual dimorphism could be mediated at least in part by gonadal hormones. In female rats, ovarian hormones fluctuate over a 4 to 5 day cycle characterized by
Summary and conclusions
The current literature describes sex differences in dendritic morphology of pyramidal neurons in medial prefrontal cortex and spine density in basolateral amygdala, as well as sex differences in behavioral responses during fear conditioning and extinction. While chronic stress effects on these variables are well-documented in males, the data on females is sparse. Nonetheless, these data show that there are sex differences in dendritic morphology within the prelimbic and infralimbic regions of
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