Effect of various stressors on the blood ACTH and corticosterone concentration in normotensive Wistar and spontaneously hypertensive Wistar-Kyoto rats.

The role of the sympathetic nervous system (SNS) and the hypothalamo-pituitary-adrenal (HPA) axis in the stress response is well documented. The imbalance in a central and peripheral SNS activity accompanied by the HPA hyperresponsivity has been observed in essential and experimental hypertension. The spontaneously hypertensive rats (SHR) are extensively used in studying mechanisms of the essential hypertension. The blood ACTH and corticosterone concentration was examined in spontaneously hypertensive (Wistar-Kyoto) and normotensive (Wistar) adult male rats exposed to acute cold (2h) or immobilization (2h) stress as well as chronic (21days) isolation stress or their combination. The present results show that SHR in basal conditions have higher blood ACTH and corticosterone level as compared to the normotensive rats. Both the acute exposure to cold and immobilization stress induced a higher increment in SHR plasma ACTH in respect to Wistar rats. The similar pattern of ACTH response occurred when SHR were previously chronically isolated and acutely exposed to both applied stressors. Surprisingly, corticosterone concentration did not differ between control rats with or without 21days isolation or those exposed to a cold or immobile acute stressor.