Menthol inhibits 5-HT3 receptor-mediated currents

Area of Science:

• Pharmacology
• Neuroscience
• Molecular Biology

Background:

• Menthol, derived from peppermint, is a key component with known physiological effects.
• Human 5-hydroxytryptamine type 3 (5-HT3) receptors are crucial ion channels involved in neurotransmission.
• Understanding menthol's interaction with 5-HT3 receptors can elucidate its pharmacological actions.

Purpose of the Study:

• To investigate the effects of menthol on the function of human 5-HT3 receptors.
• To determine the mechanism and characteristics of menthol's interaction with these receptors.

Main Methods:

• Two-electrode voltage-clamp technique in Xenopus laevis oocytes expressing human 5-HT3 receptors.
• Concentration-dependent inhibition assays.
• G-protein activity assays and pertussis toxin sensitivity tests.
• Radioligand binding assays using [(3)H]GR65630.
• Electrophysiological recordings in acutely dissociated nodose ganglion neurons.

Main Results:

• Menthol reversibly inhibited 5-HT3 receptor currents in a concentration-dependent manner (IC50 = 163 μM).
• The inhibitory effect was not stereoselective and did not involve G-proteins.
• Menthol acted as a noncompetitive antagonist, as evidenced by unaltered radioligand binding and lack of reversal by increased 5-HT.
• Menthol also inhibited 5-HT3 receptor-mediated currents in native neurons.

Conclusions:

• Menthol acts as a noncompetitive, allosteric inhibitor of human 5-HT3 receptors.
• These findings suggest menthol modulates neuronal signaling through 5-HT3 receptor antagonism at pharmacologically relevant concentrations.