Histamine H_1-receptor-mediated increase in the Ca~2+ transient without a change in the Ca~2+ current in electrically stimulated guinea-pig atrial myocytes

摘要

The effect of histamine on the intracellular Ca~2+ concentration([Ca~2+]I), action potential and membrane currents were assessed in single atrial myocytes prepared from guinea-pigs. Histamine caused a concentration-dependent increase in the [Ca~2+]I transient in indol/AM loaded Myocytes when stimulated electrically at 0.5 Hz. However, the maximum increase in [Ca~2+]I transient Produced by histamine was less than 50/100 of the elicited by isoprenaline. The histamine-induced Increase in [Ca~2+]I transient was significantly inhibited by chlorpheniramine, but not by cimetidine. Pretreatment with nifedipine nearly completely suppressed the histamine-induced increase in [Ca~2+]I Transient. Cyclopiazonic acid did not affect the histamine response.