Interaction between Antinociceptive Effects of Preventive Microwave Irradiation of an Acupuncture Point and Pharmacological Blocking of NO Synthase in Mice

Abstract

In behavioral experiments on four groups of mice under conditions of a standard formalin test, we examined effects produced by preliminary 10-min-long irradiation of the acupuncture point (AP) E-36 by low-intensity millimeter electromagnetic waves. Fifty-msec-long bursts filled with oscillations of varying frequency (wavelength from 4.0 to 7.5 mm) were separated by 50-msec-long intervals. The respective effects were compared with those resulting from blocking of NO synthase, NOS (injections of 20 mg/kg of a competitive NOS blocker, L-NAME). In the cases of isolated preventive AP irradiation and normal functioning of NO synthase, behavioral manifestations of the pain reaction (licking of the limb subjected to subcutaneous injection of formalin in the foot) were significantly suppressed within nearly the entire period of observation (60 min); the relative intensity of such suppression within a 30 to 50 min interval was greater than that within initial 20 min of the development of pain. Isolated blocking of NOS resulted in a more than twofold decrease of the duration of licking episodes within the initial phase of the pain reaction (up to 20 min), however, within a 30 to 40 min interval after injection of formalin (inflammatory pain), the intensity of such behavioral manifestations noticeably increased. A combination of preliminary irradiation of the AP E-36 and introduction of L-NAME resulted in significant intensification of analgesic effects within the entire observation period; within a 40 to 50 min interval, practically complete analgesia was provided. The total duration of manifestations of the pain reaction within the observation period under conditions of such combined action was, on average, 56% smaller than the analogous index in the formalin test performed in the absence of the analgesic influences (AP irradiation and NOS blocking). The existing concepts on the mechanisms mediating the effects of electromagnetic extremely high-frequency alternative fields on the organism of mammals, including the action of such factors on the APs, and also on the mechanisms of interaction between the effects of microwave irradiation and modulation of the intensity of NO synthesis, are discussed.