This in vivo study was conducted to 1.) determine whether millimeter wave treatment induced hypoalgesia depends on the frequency of the millimeter wave and 2.) to define what types of opioid receptors are predominantly involved in the development of millimeter wave treatment induced hypoalgesia.
Male mice (18-20 g) were examined in two experimental models: 1.) the cold water tail-flick test (experimental model of chronic non-neuropathic pain), and 2.) the chronic constriction injury test (experimental model of chronic neuropathic pain following unilateral injury to the sciatic nerve).
Selective opioid receptor blockers (μ, δ, and κ receptor blockers) were used to define the types of opioid receptors which are involved in the development of the millimeter wave treatment induced hypoalgesia.
| Exposure | Parameters |
|---|---|
|
Exposure 1:
42.25–61.22 GHz
Exposure duration:
continuous for 15 min
|
|
| Frequency | 42.25–61.22 GHz |
|---|---|
| Type | |
| Exposure duration | continuous for 15 min |
| Exposure source | |
|---|---|
| Distance between exposed object and exposure source | 1 mm |
| Sham exposure | A sham exposure was conducted. |
| Measurand | Value | Type | Method | Mass | Remarks |
|---|---|---|---|---|---|
| power density | 13.3 mW/cm² | - | - | - | - |
The millimeter wave treatment statistically significantly decreased frequency dependent the level of both cold water induced pain and chronic neuropathic pain in mice. This effect was most pronounced when the frequency of 61.22 GHz was used.
The response to millimeter wave treatment was significantly decreased in mice which were pretreated with selective μ and δ receptor blockers. The concentration of the endogenous opioid enkephalin was significantly higher in midbrain and hypothalamus area.
These results indicate that the system of endogenous opioids seems to play an important role in the systemic effects of the millimeter wave treatment.
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