ANTIPRURITIC EFFECT OF MILLIMETER WAVES IN MICE - EVIDENCE FOR OPIOIDINVOLVEMENT

In our previous studies, exposure of mice to millimeter waves (MW) inc reased the duration of anesthesia caused by either ketamine or chloral hydrate, and this effect was blocked by naloxone. To further characte rize the biological effects of MW, we have chosen a new animal model o f experimental itch. Male Swiss albino mice were injected s.c. in the rostral part of the back with the pruritogenic agent, compound 48/80, with or without naloxone pretreatment. After a 15-min exposure of mice to MW (frequency, 61.22 GHz; incident power density, 15 mW/cm(2)), th e number of scratches of the injected site was counted for 90 min post -injection. MW inhibited the scratching activity of mice by more than 2 times in comparison with the sham-exposed controls (p<0.005). Pretre atment of animals with (-)-naloxone (0.1-1.0 mg/kg, i.p.) suppressed t he antipruritic effect of MW in a dose-dependent manner, while the ina ctive enantiomer (+)-naloxone at 1 mg/kg did not alter the effect. The se results suggest that MW trigger the release of opioids in exposed s ubjects. (C) 1998 Elsevier Science Inc.