Background: Exposure to stress involves activation of the paraventricular nucleus of the hypothalamus (PVN) leading to activation of the hypothalamic-pituitary axis and sympathetic nervous system.
Methods: We examined which brain regions were activated following exposure to chronic stress (60 mins air-jet repeated daily for 7 days) in rabbits treated with chronic (6 week) low dose angiotensin II (Ang II, 20ng/kg/min) and sham treated control rabbits.
Results: Greater MAP responses following chronic stress exposure in rabbits pretreated with Ang II (64.7±1.2 v 76.9±2.9, P<0.01) were associated with greater neuronal activation (Fos expression induced by exposure to 60 mins air-jet stress on day 7) in the PVN (15.7±3.3 v 39.1±3.1, P<0.001) compared with sham controls. However, no difference in Fos expression was observed in the amygdala, dorsomedial hypothalamus, arcuate and supraoptic nuclei between groups. Similar numbers of neurons in the PVN of both groups exposed to chronic stress were found to contain corticotrophin releasing factor and vasopressin. While many activated neurons in the PVN of all rabbits also expressed markers for NADPH oxidase and nitric oxide synthase (NOS), there were greater numbers of activated NADPH oxidase (11.1±2.9 v 17.5±5.3, P<0.01) and NOS (16.1±3.2 v 45.3±3.9, P<0.001) labeled neurons following chronic stress in rabbits pretreated with Ang II.
Conclusions: These results indicate that, in addition to activation of stress hormones, superoxide and NO production, the PVN is also associated with elevated MAP responses to chronic stress exposure in Ang II-induced hypertensive rabbits.
Disclosure: none.