Analgesia Induced by Microwave Irradiation of an Acupuncture Point under Conditions of Visceral Pain in Mice: Role of the Serotonergic Cerebral System

Abstract

We studied behavioral manifestations of analgesic effects induced in mice by irradiation of the E36 acupuncture point (AcP) by low-intensity microwaves under conditions of visceral pain evoked by i.p. injections of 0.08 ml of a 2% solution of acetic acid. We also examined changes in these analgesic effects resulting from a drop in the level of serotonin after i.p. injection of 300 mg/kg of a blocker of synthesis of serotonin, DL-parachlorophenylalanine (PChPhA). Two modes of irradiation were tested, with a wide frequency range (30 to 300 GHz) and amplitude modulation (mode 1) and with a stable frequency (61 ± ± 4 GHz, mode 2). Irradiation in mode 1 provided a higher level of analgesia than that in mode 2 (decreases in the duration of manifestations of the pain reaction were, on average, 35.7 and 20.4%, respectively). The level of analgesia dropped after injections of PChPhA; the durations of behavioral pain manifestations 24 h after such injections were greater than those in the group with no injections of the blocker by 41.3 and 12.1% in irradiation modes 1 and 2, respectively. The respective figures 48 h after PChPhA injections were 52.0 and 16.1%. Thus, under conditions of visceral pain, irradiation of the AcP by low-intensity microwaves provides noticeable analgesia, and the serotonergic brain system mediates the development of analgesia under the above-mentioned conditions.

Combination of pharmacological analgesics and microwave irradiation of an acupuncture point for suppression of visceral pain in mice: Role of the opioid and serotonergic cerebral systems

“…This effect is indicative of the development of rather intense analgesia after microwave irradiation of the antinociceptive AP; these findings agree well with the experimental data obtained by other researchers [18].…”

“…In our previous studies [18,26] we demonstrated that the serotonergic system is significantly involved in the formation of the antinociceptive effect of microwaves. It was also shown that an additional mechanism of the action of analgin independent of inhibition of the activity of cyclooxygenase is related to activation of descending serotonergic pathways involved in the control of nociception [27].…”

Analgesia induced by combined action of Tramadol and microwave irradiation in somatic pain in mice

“…This fact is, perhaps, related to summation of the actions of microwaves and tramadol on the central antinociceptive systems. It was found that the analgesic effect of microwave irradiation is mediated by serotonergic [9][10][11] and opioidergic [17,18] cerebral systems. Tramadol hydrochloride is a centrally acting analgesic with a complex mechanism of action: on the one hand, it is bound with μ-opioid receptors, while, on the other hand, it suppresses reuptake of noradrenalin by neuronal axon terminals and enhances the release of serotonin.…”

“…Data obtained in experiments on animals [8][9][10][11], as well as results of treatment of patients with chronic pain syndromes [12,13], have demonstrated that there is an approach that provides weakening and, in some cases, even complete suppression of the pain syndromes; this is the action of low-intensity microwaves (with a nonthermal effect) on acupuncture points (APs). In our study, we examined the anesthetic effects of a synthetic opioid, tramadol, and microwave irradiation of an antinociceptive AP in mice.…”