Seasonal variation in the development of stress-induced systolic hypertension in the rat
Weinstock, M.; Blotnick, S.; Segal, M.
Journal of Hypertension. Suppl Official Journal of the International Society of Hypertension 3(3): S107-S109
1985
ISSN/ISBN: 0952-1178 PMID: 2856682 Document Number: 266792
Seasonal variation in blood pressure in human hypertensives prompted us to investigate whether such a phenomenon also occurs in rats made hypertensive by environmental stress. Groups of eight to 20 rats, housed in stress chamber under natural light conditions at 21 +/- 1 degree C, were subjected to noise (85-105 dB) and light stress for 4 h three times per week for 16 weeks, over 4 years. Systolic pressure increased by 14-25 mmHg after 6-8 weeks of stress from October to January. Artificial environmental light for 15 h prevented development of hypertension by stress, which could also be reversed by acute administration of propranolol. Hypertensive rats had significantly greater relative heart and adrenal weights. This phenomenon can be explained by amplification of sympathetic pressor activity by stress hormones, adrenaline, corticosterone and prolactin, under the influence of melatonin.