Effects of autonomic blockers on linear and nonlinear indexes of blood pressure and heart rate in SHR

Recent results in normotensive Wistar-Kyoto (WKY) rats show that nonlinear method may be more specific to quantify sympathetic and parasympathetic act ivities than the low (LF) and high frequencies (HF) spectral powers of bloo d pressure (BP) and R-R interval (RR). The present study extends this concl usion to spontaneously hypertensive rats (SHR). Blood pressure was recorded for 30 min before and after intravenous injection of saline, hexamethonium , atropine, atenolol, or prazosin. Mean level, standard deviation (SD), spe ctral LF and HIP components, and three nonlinear indexes (percentage of rec urrence, percentage of determinism, and length index of the recurrence plot method) were used to analyze the BP and RR signals. In conscious SHR, symp athetic but not parasympathetic blockade reduced BP level and LF-BP, and in creased nonlinear indexes of BP. RR increased after beta -sympathetic and g anglionic blockade, decreased after parasympathetic blockade, and remained unchanged after alpha (1)-sympathetic blockade. SD-RR decreased after gangl ionic and alpha (1) blockade, whereas HF-RR increased after beta -sympathet ic blockade. The effects on nonlinear indexes of RR are clear and consisten t: only al-blockade increased the indexes. Our nonlinear indexes may be use ful to investigate cardiovascular functions in normotension and hypertensio n.