title: Does the sympathetic nervous system influence sinus arrhythmia in man? Evidence from combined autonomic blockade.
abstract: The influences of vagal and sympathetic efferent activity on sinus arrhythmia in man have been studied in healthy subjects by administration of hyoscine butylbromide and atenolol alone and combined using a microcomputer-linked electrocardiogram (e.c.g.) system. Sinus arrhythmia was quantitated as the S.D. of the R-R interval. Sinus arrhythmia was reduced by hyoscine butylbromide, in some subjects to near abolition, but this end-point was unchanged by pre-treatment with atenolol. Atenolol alone prolonged the mean R-R interval and increased sinus arrhythmia. It is suggested that sinus arrhythmia in man is mediated through vagal efferents alone but that atenolol increases the arrhythmia through a central vagotonic effect.
mesh_terms: D000328:Adult; D001146:Arrhythmia, Sinus / Q000139:chemically induced / Q000503:physiopathology*; D001262:Atenolol / Q000494:pharmacology; D001340:Autonomic Nerve Block; D002086:Butylscopolammonium Bromide / Q000494:pharmacology; D004525:Efferent Pathways / Q000503:physiopathology; D004562:Electrocardiography; D005260:Female; D006801:Humans; D008297:Male; D013564:Sympathetic Nervous System / Q000187:drug effects / Q000503:physiopathology*
chemical_list: D002086:Butylscopolammonium Bromide; D001262:Atenolol