| Abstract: | Basic autonomic nervous function was evaluated in patients with neurocardiogenic syncope (NCS). Atropine, isoproterenol, propranolol, phenylephrine, and phentolamine were administered successively, and parasympathetic nerve activity and beta- (and alpha-) activity, sensitivity, and secretion of the sympathetic nerve were determined in patients with NCS and control subjects. In patients with NCS, beta- and alpha- sensitivity were higher and beta-activity and beta- and alpha-secretion lower than in control subjects. In patients with NCS, the increased basic beta-sensitivity may contribute to induce strong cardiac contractions and augment ventricular mechanoreceptor response, and a compensatory state against diminished neuronal sympathetic activity is suggested by the increased alpha-sensitivity. |
