Involvement of central angiotensin receptors in stress adaptation

The present study examined the effects of acute and chronic neurogenic stre ssors on the expression of two distinct angiotensin receptors in two stress -related brain nuclei: angiotensin type 1A receptor in the paraventricular nucleus of the hypothalamus and angiotensin type 2 receptor in the nucleus locus coeruleus. Male Wistar rats were divided into four experimental group s. The first two groups were subjected once to an acute 90-min immobilizati on or air-jet stress session, respectively. The other two groups were subje cted to 10 days of daily 90-min immobilization sessions and, on the 11th da y, one group was exposed to an additional 90-min immobilization and the oth er to a single air-jet stress (heterotypic but still neurogenic) session. I n each group, rats were perfused before stress (0 min), immediately followi ng stress (90 min) or 150, 180, 270 or 360 min land 24 h in chronic immobil ization after the beginning of the last stress session. Basal expression of both angiotensin receptor subtype 1A and angiotensin receptor subtype 2 me ssenger RNA was minimal in non-stressed animals. Acute immobilization as we ll as air-jet stress induced similar patterns (time-course and maximal valu es) of angiotensin receptor subtype 1A messenger RNA expression in the para ventricular nucleus. Angiotensin receptor subtype 1A messenger RNA expressi on increased 90-150 min after the beginning of the stress and returned to b asal levels by 360 min. Chronic stress immobilization slightly modified the pattern, but not maximal values of angiotensin receptor subtype 1A messeng er RNA expression to further immobilization (homotypic) or air-jet stress ( heterotypic). Acute immobilization and air-jet stress sessions induced simi lar locus coeruleus-specific angiotensin receptor subtype 2 messenger RNA e xpression. This expression increased 90 min following the onset of the stre ss session and remained elevated for at least 360 min. Chronic immobilizati on stress increased angiotensin receptor subtype 2 messenger RNA expression to levels comparable to those observed in acute stress conditions. Novel a cute exposure to neurogenic stressors did not further increase these levels in either homotypic (immobilization) or in heterotypic (air-jet stress) co nditions. These results suggest that central angiotensin receptors are targ ets of regulation in stress; therefore, stress may modulate angiotensin fun ction in the paraventricular nucleus and locus coeruleus during chronic exp osure to neurogenic stressors. (C) 1999 IBRO. Published by Elsevier Science Ltd.