Sex differences in social stress-induced pressor and behavioral responses in normotensive and prehypertensive rats.

This study investigated sex differences in chronic social stress-induced pressor and behavioral responses in normotensive and prehypertensive rats. Adult Wistar and borderline hypertensive (BH) rats (offspring of Wistar dams and spontaneously hypertensive sires) of both sexes were exposed to crowding stress (200 cm²/rat, 5 rats/cage) for 6 weeks. Controls were kept 4 rats/cage (480 cm²/rat). Blood pressure (BP) and open field activity were determined before experiment and after 1, 3 and 6 weeks of stress. Basal BP of BH rats was higher than in Wistar (p < 0.001) in both males and females. Horizontal and vertical activity of BH males and females was elevated vs. Wistar (p < 0.01) and females in both phenotypes were more active than the respective males (p < 0.01). Crowding resulted in delayed between-session habituation and significant elevation of BP only in BH males (143 ± 2 vs. 134 ± 3 mmHg in controls after 6-week crowding). No changes of BP were observed in crowded females of both phenotypes regardless of their delayed between-session habituation. Thus chronic social stress produced by crowding seems to represent a significant risk factor for development of stress-related hypertension only in males with genetic predisposition to high blood pressure while females of both phenotypes responded to stress by impaired between-session habituation.