DIFFERENTIAL REGULATION OF CARDIAC ALPHA-ADRENOCEPTOR AND BETA-ADRENOCEPTOR BY THE SYMPATHETIC NERVOUS-SYSTEM

1 The effects of depressed sympathetic function on the inotropic respo nses of the heart to sympathomimetic amines have been examined in rats immunized against nerve growth factor (NGF) 6 weeks prior to the isol ation of cardiac tissues. 2 The activity of tyrosine hydroxylase in ce rvical sympathetic ganglia and the levels of noradrenaline in ventricu lar tissue were significantly reduced in NGF-immunized rats. 3 Left at ria and papillary muscles from NGF-immunized rats were supersensitive to the beta-adrenoceptor agonist isoprenaline when compared with contr ols. 4 The responses of cardiac tissues to the alpha-adrenoceptor agon ist phenylephrine were unaffected by immunization. 5 These results sup port the,hypothesis that cardiac beta- but not alpha-adrenoceptor sens itivity is regulated by the sympathetic nervous system.