Verapamil and nifedipine effect on K+-induced contractions of guinea pig ileum during postnatal development

The effects of verapamil and nifedipine on K+-induced contractions were studied in the isolated ileum of newborn, 30-day-old and adult guinea pigs. Both verapamil and nifedipine inhibited the K+-induced contractions, with nifedipine demonstrating the highest activity. The tonic component of the K+ response was more affected by the calcium antagonists than the phasic component. No changes in sensitivity to verapamil and nifedipine were recorded during the first month of postnatal development, thus suggesting that the function of calcium channels involved in the response to K+ does not change during this period.