Intravenous injection of ZD 7288, a new specific hyperpolarizing current blocker, dose-dependently reduces heart rate in adult rats. The autonomic nervous system modulates changes in heart rate caused by hyperpolarizing currents.

Prepubertal period in rats is characterized by some peculiarities of the cardiac regulatory mechanisms. In 6-week-old rats atropine produced bradycardia instead of tachycardia. Similar reaction was not observed in chemically ...