Normalized entropy applied to the study of sex differences in cardiovascular stress-response to atropine and propranolol in rats

The cardiovascular sensitivity of normal anal stressed rats to sympathetic and parasympathetic blockades was greater in females than in males when studied using the heart rate, mean arterial pressure and normalized entropy (a new measure of the complexity degree of blood pressure signals). It is supported that sympathetic and parasympathetic influences on the cardiovascular system are more pronounced in females than in males under both normal and stress conditions. Normalized entropy was demonstrated to be a more sensitive marker of gender and individual differences in cardiovascular responses to external and internal perturbations.