Development of the muscarinic potassium current in fetal and
neonatal rat heart.
Takano, Makoto, and Akinori Noma.
Department of Physiology & Biophysics, Faculty of Medicine,
Kyoto University, Kyoto, 606-01 Japan, Tel: -81-(0)75-753-4352, Fax:
-81-(0)75-753-4349, E-mail: takano@med.kyoto-u.ac.jp
APStracts 3:0456H, 1996.
Single atrial myocytes were isolated from fetal, neonatal and adult
rat hearts. The muscarinic K+ current activated by rapid application
of acetylcholine (ACh) and adenosine (Ado) was recorded under the
whole cell voltage clamp. The current density (pA/pF) of ACh-induced
K+ current increased from gestation day 12 to the maximum on neonatal
day 20, and decreased in the adult myocytes due to greater increase
of the membrane capacitance. Development of Ado-induced K+ current
followed similar time course except remarkable decrease after
neonatal day 10. No significant change was found in single channel
properties during the development. Receptor subtypes were M2- and A1
-receptors for ACh and Ado, respectively. In the dose-response
relationship, the half-maximal concentration for ACh-induced current
markedly decreased with age, from 1.44 [mu]M (fetus) to 0.17 [mu]M
(adult), while that for Ado increased from 0.45 [mu]M (fetus) to 0.99
[mu]M (adult). These changes of the muscarinic K+ current were
discussed in relation to the functional development of cardiac
myocytes, and underlying mechanisms.
Received 16 April 1996; accepted in final form 9 October 1996.
APS Manuscript Number H342-6.
Article publication pending Am. J. Physiol. (Heart Circ. Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 5 November 1996