Insight into the Neural Circuitry Underlying Habituation to Stress

      Habituation to stress is a process that possibly diminishes the detrimental health consequences of chronic stress by reducing the amplitude of many responses when the same challenging conditions are experienced repeatedly. 

Stress triggers neuroendocrine, autonomic, and behavioral responses that typically help organisms maintain homeostasis and promote survival. The benefits of acute stress responses can be diminished under chronic stress conditions and can be associated with somatic and psychological disorders. Stress habituation can help mitigate the effects of chronic stress. It can weaken or eliminate stress responses to the same stressor experienced repeatedly. The understanding around the neural circuitry and cellular mechanisms underlying habituation to stress is limited. 

The current study provides some of the first anatomical and functional results suggesting that a specific region of the hypothalamus, the rostral posterior hypothalamic nucleus, targets multiple premotor regions and contributes to the regulation of acute neuroendocrine responses and their habituation to repeated stress. This revealed a rostral portion of the posterior hypothalamic nucleus as a major origin of stress-active projections to both the medial parvicellular region of the paraventricular hypothalamic nucleus and rostral medullary raphe pallidus. This region inactivated using the GABA receptor agonist muscimol to test the rostral region of the posterior hypothalamic nucleus in acute audiogenic stress-induced HPA axis responses and their habituation to the audiogenic stress exposure. This suggests a notable contribution of the rostral posterior hypothalamic nucleus in HPA axis habituation. 

Overall, this places the rostral posterior hypothalamus in a central position to integrate multiple sources of sensory, homeostatic, and limbic information, and use this information to coordinate and modify multiple responses triggered by stress. Based on these initial findings, it will be important to further assess the role of the rostral region of the posterior hypothalamic nucleus on stress habituation of multiple responses assessed simultaneously to test fully the generality of the proposed stress integrative function of this region.

Campeau, Serge, et al. Correction: Nyhuis Et Al., Evidence for the Integration of Stress-Related Signals by the Rostral Posterior Hypothalamic Nucleus in the Regulation of Acute and Repeated Stress-Evoked Hypothalamo-Pituitary-Adrenal Response in Rat. The Journal of Neuroscience, vol. 36, no. 18, 2016, doi:10.1523/jneurosci.1273-16.2016.