Exercise-Induced Adrenocorticotropic Hormone Response Is Cooperatively Regulated by Hypothalamic Arginine Vasopressin and Corticotrophin-Releasing Hormone

Introduction: Exercise becomes a stress when performed at an intensity above the lactate threshold (LT) because at that point the plasma adrenocorticotropic hormone (ACTH), a marker of stress response, increases. It is possible that the exercise-induced ACTH response is regulated at least by arginine vasopressin (AVP) and possibly by corticotropin-releasing hormone (CRH), but this remains unclear. To clarify the involvement of these factors, it is useful to intervene pharmacologically in the regulatory mechanisms, with a physiologically acceptable exercise model. Methods: We used a special stress model of treadmill running (aerobic exercise) for male Wistar rats, which mimic the human physiological response, where plasma ACTH levels increase at just above the LT for 30 min. Animals were administered the AVP V-1b receptor antagonist SSR149415 (SSR) and/or the CRH type 1 receptor antagonist CP154526 (CP) intraperitoneally before the exercise, which allowed the monitoring of exercise-induced ACTH response. Immunohistochemical evaluation of activated AVP and CRH neurons with exercise was performed for the animals' hypothalami. Results: A single injection of either antagonist, SSR or CP, resulted in inhibited ACTH levels after exercise stress. Moreover, the combined injection of SSR and CP strongly suppressed ACTH secretion during treadmill running to a greater extent than each alone. The running-exercise-induced activation of both AVP and CRH neurons in the hypothalamus was also confirmed. Conclusion: These results lead us to hypothesize that AVP and CRH are cooperatively involved in exercise-induced ACTH response just above the LT. This may also reflect the stress response with moderate-intensity exercise in humans. (C) 2021 S. Karger AG, Basel

Automated summary

Exercise at an intensity above the lactate threshold leads to an increase in plasma adrenocorticotropic hormone (ACTH), indicating a stress response. This study investigated the involvement of arginine vasopressin (AVP) and corticotropin-releasing hormone (CRH) in regulating exercise-induced ACTH response. Using a rat model, the researchers administered AVP and CRH receptor antagonists and observed a suppression of ACTH levels after exercise. Immunohistochemical evaluation confirmed the activation of AVP and CRH neurons in the hypothalamus. These findings suggest that AVP and CRH cooperatively contribute to exercise-induced ACTH response, reflecting the stress response to moderate-intensity exercise in humans.