Evidence of alpha-adrenoceptor-mediated chronotropic action in children.
We investigated alpha-adrenoceptor-mediated positive chronotropic action in children using a pharmacological autonomic function test. Under cardiac vagal and sympathetic blockade, chronotropic responses to intravenous infusion of an alpha-agonist, phenylephrine, were determined in 129 patients with suspected autonomic dysfunction. Heart rate changes to phenylephrine infusion (0.4 microg/kg/min) for 5 minutes ranged from -2 to 50 beats/min (mean +/- SD, 13.8 +/- 9.7 beats/min). alpha-Adrenoceptor-mediated chronotropic (APC) action more than 5 beats/min was observed in 88 (68%) subjects. APC was negatively correlated with age. Multivariate analysis showed that APC was correlated negatively with beta-sympathetic tone and positively correlated with intrinsic heart rate. These results suggest that the alpha-adrenoceptor-mediated chronotropic action is a developmental phenomenon and may play an important role in controlling heart rate in response to cardiac sympathetic activation.
Tanaka
H
H
Department of Pediatrics, Osaka Medical College, 2-7, Daigakucho, Takatsuki-shi, Osaka, Japan 569.
Takenaka
Y
Y
Yamaguchi
H
H
Mino
M
M
Tamai
H
H
D000293:Adolescent; D000316:Adrenergic alpha-Agonists / Q000494:pharmacology*; D000317:Adrenergic alpha-Antagonists / Q000494:pharmacology; D001285:Atropine / Q000494:pharmacology; D001342:Autonomic Nervous System Diseases / Q000503:physiopathology*; D002648:Child; D002675:Child, Preschool; D005260:Female; D006339:Heart Rate / Q000187:drug effects / Q000502:physiology*; D006801:Humans; D007545:Isoproterenol / Q000494:pharmacology; D008297:Male; D015999:Multivariate Analysis; D009200:Myocardial Contraction / Q000187:drug effects*; D010646:Phentolamine / Q000494:pharmacology; D010656:Phenylephrine / Q000494:pharmacology; D011433:Propranolol / Q000494:pharmacology; D011942:Receptors, Adrenergic, alpha / Q000502:physiology*; D012044:Regression Analysis; D013575:Syncope / Q000503:physiopathology
D000316:Adrenergic alpha-Agonists; D000317:Adrenergic alpha-Antagonists; D011942:Receptors, Adrenergic, alpha; D010656:Phenylephrine; D001285:Atropine; D011433:Propranolol; D007545:Isoproterenol; D010646:Phentolamine