N. Agata et al., DEVELOPMENTAL-CHANGES IN ACTION-POTENTIAL PROPERTIES OF THE GUINEA-PIG MYOCARDIUM, Acta Physiologica Scandinavica, 149(3), 1993, pp. 331-337
Developmental changes in action potential properties were examined in
electrically driven (I Hz) left atria and right ventricles from foetal
, neonatal and adult guinea-pig hearts, using standard micro-electrode
recording techniques. In both left atria and right ventricles, the ov
ershoot, resting potential and maximum upstroke velocity of the action
potential increased progressively with age until birth, and then rema
ined almost unchanged. Action potential duration (APD) changed markedl
y with age during foetal and neonatal periods. In left atria, APD at 5
0% repolarization initially decreased until foetal day 50, and then in
creased until the adult period. In right ventricles, APD initially inc
reased until approximately foetal day 45, then decreased for 5 days fo
llowing birth, thereafter it increased again. In addition, after-hyper
polarization was observed only in left atria of younger foetuses. Thus
we have demonstrated that in the guinea-pig myocardium developmental
changes in action potential properties occur more extensively during t
he foetal period than during the postnatal period.