title: Effects of autonomic blockade on non-linear cardiovascular variability indices in rats.
abstract: 1. The present study assesses the effects of autonomic blockade (alpha- and beta-adrenoceptor and cholinergic) on cardiovascular function studied by heart rate variability (HRV), blood pressure variability (BPV) and baroreflex sensitivity in rats using non-linear dynamics. Little is known about the influence of pharmacological autonomic nervous system interventions on non-linear cardiovascular regulatory indices. 2. In 13 conscious rats, heart rate and aortic blood pressure were measured continuously before, during and after autonomic blockade with atropine, phentolamine and propranolol. Non-linear scaling properties were studied using 1/f slope, fractal dimension and long- and short-term correlation. Non-linear complexity was described with correlation dimension, Lyapunov exponent and approximate entropy. Non-linear indices were compared with linear time and frequency domain indices. 3. Beta-adrenoceptor blockade did not alter the non-linear characteristics of HRV and BPV, although low-frequency power of HRV was depressed. Alpha-adrenoceptor blockade decreased the scaling behaviour of HRV, whereas cholinergic blockade decreased the complexity of the non-linear system of HRV. For BPV, the scaling behaviour was increased during alpha-adrenoceptor blockade and the complexity was increased during cholinergic blockade. The linear indices of HRV and BPV were decreased. 4. The present results indicate that the beta-adrenoceptor system has little involvement in the generation of non-linear HRV and BPV in rats. 5. Alpha-adrenoceptor blockade mostly influenced the scaling properties of the time series, whereas cholinergic blockade induced changes in the complexity measures. 6. The absence of the baroreflex mechanism can trigger a compensatory feed-forward system increasing the complexity of BPV.
authors.affiliation: Laboratory of Experimental Cardiology, School of Medicine, Gasthuisberg University Hospital, KU Leuven, Leuven, Belgium. andre.aubert@med.kuleuven.ac.be
authors.forename: Frank
authors.initials: F
authors.lastname: Beckers
authors.forename: Bart
authors.initials: B
authors.lastname: Verheyden
authors.forename: Dirk
authors.initials: D
authors.lastname: Ramaekers
authors.forename: Bernard
authors.initials: B
authors.lastname: Swynghedauw
authors.forename: André E
authors.initials: AE
authors.lastname: Aubert
mesh_terms: D000317:Adrenergic alpha-Antagonists / Q000494:pharmacology*; D000319:Adrenergic beta-Antagonists / Q000494:pharmacology; D000818:Animals; D001285:Atropine / Q000494:pharmacology; D001341:Autonomic Nervous System / Q000187:drug effects*; D017704:Baroreflex; D001794:Blood Pressure; D017709:Fractals; D006339:Heart Rate; D008297:Male; D008955:Models, Cardiovascular; D018727:Muscarinic Antagonists / Q000494:pharmacology*; D017711:Nonlinear Dynamics; D010646:Phentolamine / Q000494:pharmacology; D011433:Propranolol / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar
chemical_list: D000317:Adrenergic alpha-Antagonists; D000319:Adrenergic beta-Antagonists; D018727:Muscarinic Antagonists; D001285:Atropine; D011433:Propranolol; D010646:Phentolamine