Restraint stress modulates brain, pituitary and adrenal expression of angiotensin II AT(1A), AT(1B) and AT(2) receptors.

Angiotensin II (Ang II) AT(1) receptors are involved in the regulation of the stress response. In adult male rats, acute restraint increased AT(1A) mRNA in paraventricular nucleus. Repeated restraint increased AT(1A) mRNA and AT(1) binding in paraventricular nucleus and AT(1) binding in subfornical organ and median eminence. AT(1B) and AT(2) receptors were not expressed in brain areas involved in the stress response. Acute restraint increased anterior pituitary AT(1A) mRNA and AT(1) binding and decreased AT(1B) mRNA. During repeated restraint, the increase in AT(1A) mRNA in the anterior pituitary was maintained, but AT(1B) mRNA and AT(1) binding returned to normal levels. In adrenal zona glomerulosa, AT(1B) mRNA, AT(1) binding, AT(2) mRNA and AT(2) binding decreased during acute restraint. Receptor mRNA and binding returned to normal after repeated stress, with the exception of rebound increase in adrenal zona glomerulosa AT(2) mRNA. In adrenal medulla, AT(1A) mRNA increased and AT(2) mRNA decreased during acute restraint. AT(1A) mRNA remained increased during repeated restraint, while alterations in AT(2) mRNA were no longer present. Expression of AT(1A), AT(1B) and AT(2) receptors in the hypothalamic-pituitary-adrenal axis is tissue specific and is different in acute and repeated stress. Increased brain, pituitary and adrenomedullary AT(1A) receptor expression correlates with hypothalamic-pituitary-adrenal axis stimulation, supporting the hypothesis of Ang II, through selective AT(1A) receptor stimulation, as an important determinant of the acute and repeated stress response. Decreased adrenal zona glomerulosa and anterior pituitary AT(1B) receptors during acute stress can be interpreted as compensatory to increased stimulation by Ang II. There may be additional roles for adrenal AT(2) receptors during acute stress, possibly related to interaction or cross-talk with AT(1) receptors.