Comparison of changes in blood pressure and dipsogenic responsiveness to angiotensin II in male and female rats chronically exposed to cold

In most forms of experimentally induced hypertension in rats, females develop a less severe form of the disease than males. The objective of the present study was to compare the two genders with respect to the development of cold-induced hypertension. The results of the study indicate that both males and females develop comparable elevations of blood pressure and at approximately the same rate. Thus, the blood pressures of both groups increased significantly within 2 weeks of exposure to cold and reached similar maximal levels by the seventh week. The dipsogenic responsiveness of both groups of cold-exposed rats to acute administration of the peptide hormone, angiotensin II (AngII), was increased to approximately the same extent above that of warm-adapted counterparts, suggesting an increase in the responsiveness to AngII in the brain. To assess this possibility, the induction of the oncogene, cFos, was studied in brain following IV infusion of AngII (333 ng/kg/min). Fos-like immunoreactivity (FLI) was greater (p < 0.01) in subfornical organ, supraoptic and paraventricular hypothalamic nuclei of both cold-exposed groups compared to warm-adapted controls. Thus, both male and female rats have similar elevations of blood pressure as well as increased dipsogenic and FLI responsiveness to administration of AngII during chronic exposure to cold. Copyright (C) 1996 Elsevier Science Inc.