Heart H1 Receptors: A Positive Pump Boost?

Let's chat about histamine and heart muscle. You see, there's a debate going on about whether histamine is a friend or foe when it comes to how strong your heart pumps. Some say it strengthens the squeeze, others say it weakens it, and a few believe it doesn't do much at all. So, scientists decided to test this out on human heart tissues, giving them a little electrical pulse every second. They also looked at mice with extra histamine receptors in their hearts. Now, when they added histamine and a special drug called 2-(2-thiazolyl)-ethylamine (ThEA) to these heart tissues, things got interesting. In the mouse hearts, there was a temporary dip in strength, followed by a long-lasting boost. But in human hearts, it was all positive from the start. The strength of the heart's squeeze didn't drop before it got stronger.Interestingly, when they added a chemical called cimetidine, histamine made the human heart squeeze stronger. But when they added another chemical called mepyramine, that positive effect went away. The same happened with ThEA. It made the human heart squeeze stronger, but mepyramine blocked that effect. So, it seems like histamine is a friend to human heart muscles, making them squeeze stronger. But in mouse hearts with extra histamine receptors, it's a story of ups and downs.