Histamine receptors in the synovial microcirculation

Area of Science:

• Pharmacology
• Physiology
• Histamine Receptor Research

Background:

• Histamine influences microcirculation via H(1) and H(2) receptors.
• Synovial perfusion regulation by histamine requires further investigation.

Purpose of the Study:

• To determine the roles of H(1) and H(2) receptors in controlling synovial microcirculation.
• To assess the efficacy of H(2) receptor antagonist metiamide and H(1) receptor antagonist mepyramine in blocking histamine's action on synovial perfusion.

Main Methods:

• Synovial perfusion indirectly measured using 133-Xenon clearance half-life in canine joints.
• Administration of histamine, metiamide (H(2) antagonist), and mepyramine (H(1) antagonist) to assess their effects.

Main Results:

• Histamine increased synovial perfusion, indicated by a decreased 133-Xenon clearance half-life.
• Metiamide dose-dependently blocked histamine's effect, abolishing it at high doses.
• Mepyramine did not antagonize histamine's effect and, at certain doses, increased perfusion, possibly due to histamine release.

Conclusions:

• Evidence supports the presence of H(2) receptors, but not H(1) receptors, in the synovial microcirculation.
• H(2) receptors play a significant role in mediating histamine's effects on synovial perfusion.