Related Experiment Videos
Histamine increases the Ca current in guinea-pig ventricular myocytes
Insights
Histamine prolongs cardiac action potential duration by increasing calcium (Ca) current in guinea-pig ventricular myocytes, mediated by H2-receptors. This effect was blocked by cimetidine, indicating a specific receptor interaction.
Area of Science:
- Cardiology
- Pharmacology
- Cell Physiology
Background:
- Histamine is a biogenic amine with diverse physiological roles.
- Its effects on cardiac electrophysiology, particularly calcium currents, require further elucidation.
Purpose of the Study:
- To investigate the electrophysiological effects of histamine on guinea-pig ventricular myocytes.
- To determine the specific histamine receptor subtype involved in these cardiac actions.
Main Methods:
- Whole-cell voltage clamp techniques were employed.
- Experiments were conducted on isolated guinea-pig ventricular myocytes.
- Pharmacological agents, cimetidine and mepyramine, were used to probe receptor involvement.
Main Results:
- Histamine significantly prolonged action potential duration.
- Histamine caused an upward shift in the action potential plateau.
- An increase in the inward calcium (Ca) current amplitude was observed.
- A minor increase in outward current was also noted.
- Cimetidine, an H2-receptor antagonist, inhibited histamine's effects.
- Mepyramine, an H1-receptor antagonist, did not affect histamine's actions.
Conclusions:
- Histamine enhances the inward calcium current in ventricular myocytes.
- These effects are likely mediated through the activation of histamine H2-receptors.
- Histamine may play a role in modulating cardiac contractility via calcium current.
Abstract:
Histamine prolonged the action potential duration and shifted the plateau in an upward direction in guinea-pig ventricular myocytes. Whole cell voltage clamp experiments revealed that histamine increases the amplitude of the inward Ca current with a slight increase in the outward current. Cimetidine but not mepyramine inhibited the effects of histamine. We suggest that histamine increases the Ca current via the mediation of the H2-receptors.