Effect of the Topical External Formulation of the Low-Affinity NMDA Receptor Antagonist Hemantane on Peripheral Sensitization Induced by TRPV1 Receptor Agonist Capsaicin in Mice

The effect of the noncompetitive low-affinity NMDA receptor antagonist hemantane [N-(2-adamantyl)hexamethyleneimine hydrochloride) in two topical formulations on the peripheral sensitization induced by the TRPV1 receptor agonist capsaicin was studied in mice. Hemantane gel (5%) containing DMSO, in contrast to hemantane gel (5%) free of DMSO, did not reduce the duration of the animal reaction to subcutaneous injection of capsaicin solution applied 10 min before the injection although it was effective when applied 60 min before stimulation of TRPV1 receptors. Placebo gel containing DMSO at the same concentration (10%) as in hemantane gel (5%) with DMSO enhanced capsaicin-induced peripheral sensitization when applied 10 min but not 60 min before injection of capsaicin solution.