Early life stress downregulates endothelin receptor expression and enhances acute stress-mediated blood pressure responses in adult rats.

We hypothesized that early life stress enhances endothelin (ET-1)-dependent acute stress responses in adulthood. We utilized a unique rat model, wild-type (WT) and ET(B) receptor-deficient spotting lethal (sl/sl) rats, as well as pharmacological blockade of ET receptors, in a model of early life stress, maternal separation (MS). MS was performed in male WT and sl/sl rats 3 h/day from day 2 to 14 of life. Acute air jet stress (AJS)-induced responses (elevation in blood pressure, plasma corticosterone, and plasma ET-1) were evaluated in adult MS rats compared with the nonhandled littermate (control) rats. MS significantly augmented the acute AJS-induced blood pressure response (area under the curve) in WT rats compared with control, while the AJS-induced pressor responses were similar in sl/sl MS and control rats. ET receptor blockade significantly blunted the AJS-induced pressor response in WT MS and control rats. Moreover, AJS-induced plasma corticosterone levels in control rats were sensitive to ET receptor blockade, yet, AJS did not alter plasma corticosterone levels in MS rats. MS significantly increased circulating ET-1 levels, and AJS-induced plasma ET-1 levels were similarly increased in control and MS rats. MS induced a significant downregulation in expression of ET(A) and ET(B) receptors in aortic tissue compared with control rats. These results indicate that early life stress reduced expression of ET(A) and ET(B) receptors, leading to alterations in the ET pathway, and an exaggerated acute stress-mediated pressor response in adulthood.