Effect of β-adrenoceptor blockade on cardiac activity in rats during postnatal ontogeny

Electrical stimulation of the right stellate ganglion produces a positive chronotropic effect in 21-, 56- and 100-day-old rats. The response of the heart rate to suprathreshold stimulation increased from the 21st to 100th day. By contrast, during beta-adrenoceptor blockade the heart rate response decreased. The data suggest that the role of beta-adrenoceptor in the regulation of cardiac chronotropic function increased with age.