| pubmed-article:3737677 | pubmed:abstractText | Isolated rabbit papillary muscles that do not present pacemaker activity under physiological conditions develop a spontaneous activity in the presence of 2 mmol/l BaCl2. Ba-induced contractions were unaffected by high concentrations of the Na antagonist procainamide (10(-5) mol/l). Tetrodotoxin (10(-5) mol/l), a specific blocker of the fast Na current, only slightly increased the amplitude of contractions. In contrast, the calcium entry blockers nifedipine, diltiazem, and verapamil strongly depressed the mechanical activity in a time- and dose-dependent manner. The concentrations that decreased the amplitude and frequency of contractions by 50% were determined. The order of potency was nifedipine much greater than diltiazem greater than or equal to verapamil. Ba-induced automaticity is a particularly useful model on which the potency of calcium entry blockers could be assessed. | lld:pubmed |
