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Antipruritic effect of millimeter waves in mice: evidence for opioid involvement
M A Rojavin1, A Cowan, A A Radzievsky
1Center for Biomedical Physics and Department of Pharmacology, Temple University School of Medicine, Philadelphia, PA 19140, USA. rojavin@unix.temple.edu
Abstract:
In our previous studies, exposure of mice to millimeter waves (MW) increased the duration of anesthesia caused by either ketamine or chloral hydrate, and this effect was blocked by naloxone. To further characterize the biological effects of MW, we have chosen a new animal model of 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/cm2), the 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). Pretreatment of animals with (-)-naloxone (0.1-1.0 mg/kg, i.p.) suppressed the antipruritic effect of MW in a dose-dependent manner, while the inactive enantiomer (+)-naloxone at 1 mg/kg did not alter the effect. These results suggest that MW trigger the release of opioids in exposed subjects.
Insights
Millimeter wave (MW) exposure significantly reduced scratching behavior in mice, suggesting an antipruritic effect. This effect was dose-dependently blocked by naloxone, indicating MW may trigger opioid release.
Area of Science:
- Neuroscience
- Biophysics
Background:
- Previous studies demonstrated millimeter waves (MW) prolong anesthesia duration in mice.
- Naloxone, an opioid antagonist, blocked the anesthetic effects of MW, suggesting opioid involvement.
Purpose of the Study:
- To investigate the biological effects of MW on experimental itch in a new animal model.
- To determine if MW exposure influences opioid pathways involved in itch.
Main Methods:
- Male Swiss albino mice were injected with compound 48/80 to induce itch.
- Mice were exposed to 61.22 GHz MW at 15 mW/cm2 for 15 minutes.
- Scratching behavior was quantified for 90 minutes post-injection.
- Mice were pretreated with varying doses of (-)-naloxone or (+)-naloxone.
Main Results:
- MW exposure inhibited scratching activity by over 50% compared to controls (p<0.005).
- (-)-Naloxone pretreatment dose-dependently suppressed the antipruritic effect of MW.
- (+)-Naloxone did not affect the MW-induced inhibition of scratching.
Conclusions:
- Millimeter waves exhibit an antipruritic effect in mice.
- The findings suggest that MW exposure triggers the release of endogenous opioids.