ASSESSMENT OF SPONTANEOUS BAROREFLEX SENSITIVITY IN RATS - A NEW METHOD USING THE CONCEPT OF STATISTICAL DEPENDENCE

A new method was developed to evaluate the cardiac baroreflex sensitiv ity (BRS) from spontaneous mean arterial pressure (MAP) and heart rate (HR) changes in conscious rats. It relies on the determination of the statistical dependence between MAP and HR values. In 13 control rats, 12 rats with a pharmacologically induced hypertension, and 7 rats wit h a chronic sinoaortic denervation (SAD), dependent (MAP, HR) couples related to the baroreflex activity were selected to determine the spon taneous BRS (Sp-BRS). In control and hypertensive rats, pharmacologica l BRS (Ph-BRS) was estimated using graded bolus intravenous doses of v asoactive drugs. Ph-BRS was significantly lower in hypertensive than i n control rats. Sp-BRS was determined in 10 control and 10 hypertensiv e rats and was strongly correlated with Ph-BRS (r = 0.83, n = 20, P < 0.0001). Sp-BRS could be evaluated in six SAD rats and was profoundly decreased (-86%, P < 0.001) compared with control rats. In conclusion, this work validates the estimation of the cardiac BRS from spontaneou s MAP and HR variations with use of (MAP, HR) couples of values that a re statistically dependent.