Clinical and Applied Aspects of Magnetic Field Exposure: Possible Role for the Endogenous Opioid Systems

Evaluation of β-endorphin concentration, mood, and pain intensity in men with idiopathic hip osteoarthritis treated with variable magnetic field

Osteoarthritis is the most frequently diagnosed disease of the musculoskeletal system. Growing number of patients waiting for surgical treatment and the possible negative consequences resulting from long-term pharmacological therapy lead to the search for non-pharmacological methods aimed at alleviating pain and reducing doses of analgesics, among them physical therapy with use of magnetic fields.The study involved 30 men aged 49 to 76 (mean age, 61.7 years) treated for idiopathic osteoarthritis of the hip joint. The subjects were divided into 2 groups (15 patients each) and underwent a cycle of magnetostimulation and magnetoledtherapy procedures, respectively. During the exposure cycle concentrations of β-endorphin were assessed 3 times and the mood was assessed 2 times. In addition, the assessment of pain intensity and the dose of analgesic drugs was performed before and after the end of therapy.Statistically significant increase in plasma β-endorphins concentration was observed in both groups of patients (magnetostimulation-P < .01 vs magnetoledtherapy-P < .001). In the assessment of mood of respondents, no statistically significant differences were found. Significant reduction in intensity of perceived pain was observed in both groups of patients (P < .05). In the group of patients who underwent magnetoledtherapy cycle, the analgesic drug use was significantly lower by 13% (P < .05) as compared with initial values, which was not noted in group of patients who underwent magnetostimulation procedures.The use of magnetic field therapy in the treatment of men with idiopathic osteoarthritis of hip joints causes a statistically significant increase in the concentration of plasma β-endorphins resulting in statistically significant analgesic effect in both magnetostimulation and magnetoledtherapy treated groups of patients, with accompanying decrease of need for analgetic drugs in magnetoledtherapy group, but without any significant changes regarding the patient's mood.

Pain perception and electromagnetic fields

A substantial body of evidence has accumulated showing that exposure to electromagnetic fields (EMFs) affects pain sensitivity (nociception) and pain inhibition (analgesia). Consistent inhibitory effects of acute exposures to various EMFs on analgesia have been demonstrated in most studies. This renders examinations of changes in the expression of analgesia and nociception a particularly valuable means of addressing the biological effects of and mechanisms underlying the actions of EMFs. Here we provide an overview of the effects of various EMFs on nociceptive sensitivity and analgesia, with particular emphasis on opioid-mediated responses. We also describe the analgesic effects of particular specific EMFs, the effects of repeated exposures to EMFs and magnetic shielding, along with the dependence of EMF effects on lighting conditions. We further consider some of the underlying cellular and biophysical mechanisms along with the clinical implications of these effects of various EMFs.

No effect of 50 Hz magnetic field observed in a pilot study on pentylenetetrazol-induced seizures and mortality in mice

This study was planned so as to evaluate whether magnetic field exposure has any significant effect on the pentylenetetrazol (PTZ)-induced seizures. Mice were exposed to 50 Hz, 2 G (0.2 mT) magnetic field in glass cages for 1 h. Sham exposure was produced by turning off the current while the animals were in the same exposure volume. Then, PTZ was administered intraperitoneally (i.p.) at a dose of 60 mg/kg and the animals were observed for 30 min. Subsequently, the latency to seizure onset, total seizure duration, the number of seizure episodes and mortality were recorded for each subject. There was no evidence for a significant effect of the 50 Hz magnetic field on the mean number of PTZ induced seizures, seizure latency, total seizure duration and mortality (P>0.05). As a conclusion the present study failed to provide any further support for a therapeutic potential of magnetic field.

Naltrexone attenuates the antiparkinsonian effects of picoTesla range magnetic fields

Extracranial treatment with magnetic fields (MF) in the picoTesla range has been shown an efficacious treatment modality in the management of Parkinsonism. The mechanisms by which such extremely weak MF improve Parkinsonian symptoms are unknown. As the pineal gland has been shown to function as a "magnetosensor" and since exposure to various intensities of MF disrupts melatonin secretion, it has been proposed that the beneficial effects of MF in Parkinsonism are partly mediated through the actions of pineal melatonin. Animal studies indicate that externally applied MF also influence the activity of the opioid peptides which have been implicated in a broad range of pathological conditions including Parkinsonism. To explore whether the beneficial effects of MF in Parkinsonism involve the mediation of the opioid systems and following informed consent, we administered the opiate receptor antagonist naltrexone (50 mg, P.O.) to a Parkinsonian patient after he showed improvement of symptoms with application of MF. Results of the trial showed that naltrexone partially reversed the antiparkinsonian effects of MF thus suggesting that opioid peptides are involved in mediating the clinical effects of these extremely weak MF in Parkinsonism. These results also suggest that intact opioid systems may be required for a full expression of the antiparkinsonian effect of picoTesla range MF.

Repeated naloxone treatments and exposures to weak 60-Hz magnetic fields have 'analgesic' effects in snails

Results of studies with rodents have shown that animals repeatedly injected with the opioid antagonist, naloxone, acquire a hypoalgesic response to thermal nociceptive stimuli. The present study revealed a similar response in the terrestrial pulmonate snail, Cepaea nemoralis. Snails receiving daily injections of naloxone followed by measurements of thermal nociceptive sensitivity also developed hypoalgesia. Daily brief (30-min) exposures to a weak 60-Hz magnetic field (1.0 gauss or 0.1 mT), which acutely antagonize opioid-mediated nociception and antinociception in a manner comparable to that of naloxone, also led to the expression of a hypoalgesic responses. This suggests that opioid antagonist-induced thermal hypoalgesia may be a basic feature of opioid systems. This naloxone- and magnetic field-induced 'analgesia' is consistent with either a facilitation of aversive thermal conditioning and or antagonism of the excitatory, hyperalgesic effects of low levels of endogenous opioids.

A test for increased lethality in land snails exposed to 60 Hz magnetic fields

A recent report suggested that exposures of land snails to 0.1 mT, 60 Hz magnetic fields for periods of 48-120 h increase mortality levels by 2-10 times. In direct experimental tests, we were unable to confirm this effect.

Development of chicken embryos following exposure to 60-Hz magnetic fields with differing waveforms

Previous studies in my laboratory have revealed a reproducible and statistically significant increase in the number of malformations in live chicken embryos that had been exposed during the first 48 h of incubation to a pulsed magnetic field (unipolar pulses, 100-pps, 1-microT peak density). In marked contrast, no adverse effect was seen following similar exposure to 60-Hz, bipolar, unipolar, or split-sine waves at 3-microT peak-to-peak. In the four experiments comprising the present study, differences in the numbers of malformations between control and experimental groups were not statistically significant. Field-free incubation for an additional 72 h after exposure to a bipolar sine wave for 48 h resulted in an increase in normal live embryos in both control and treated groups.

Inhibitory effects of powerline-frequency (60-Hz) magnetic fields on pentylenetetrazol-induced seizures and mortality in rats

The possibility that exposure to powerline frequency (60-Hz) magnetic fields might affect the form or intensity of epileptic seizures, induced by administration of pentylenetetrazol (PTZ) in rats, was examined. Male adult rats were exposed to either 60-Hz magnetic fields with intensities of up to 1.85 gauss (185 microT) or to a sham field condition, for 1 h prior to injections of PTZ (45-75 mg/kg). The subsequent seizures were monitored and recorded on videotape and any subsequent mortalities were noted. Exposure to 60-Hz magnetic fields prior to administration of PTZ was found to significantly (P less than 0.005) reduce the lethality of the drug-induced seizures. The LD50 for the sham-exposed group was 65.88 mg/kg, whereas for the 60-Hz magnetic field-exposed rats, the LD50 was 85.33 mg/kg. In some experiments exposure to the 1.0 and 1.5 gauss magnetic fields also produced significant (P less than 0.05) reductions in seizure durations. These findings suggest that acute exposure to low intensity 60-Hz magnetic fields has an inhibitory effect on the lethality and expression of PTZ-induced seizures in rats. Some possible mechanisms, which could account for these observed effects of magnetic field exposure on seizures, are discussed.

Evidence for the involvement of protein kinase C in the modulation of morphine-induced 'analgesia' and the inhibitory effects of exposure to 60-Hz magnetic fields in the snail, Cepaea nemoralis

There is substantial evidence that magnetic fields can reduce opiate-induced analgesia, with alterations in calcium channel function and/or calcium ion flux being implicated in the mediation of these inhibitory effects. The present experiments were designed to examine the effects of protein kinase C (PKC), a calcium/diacylglycerol/phospholipid-dependent protein kinase, on opiate-induced analgesia and its involvement in mediating the inhibitory effects of exposure to magnetic fields. We observed that morphine-induced antinociception, or 'analgesia', in the land snail, Cepaea nemoralis, as measured by the enhanced latency of response to a thermal (38.5 degrees C) stimulus, was reduced in dose-related manner by the PKC activator, SC-9. Exposure of snails for 2 h to a low intensity (1.0 gauss rms) 60-Hz magnetic field also reduced morphine-induced analgesia. The inhibitory effects of the 60-Hz magnetic field on morphine-induced analgesia were significantly reduced by the PKC inhibitors, H-7 and H-9, and significantly enhanced by the PKC activator, SC-9. The non-specific protein kinase inhibitor, HA-1004, and the preferential calmodulin inhibitor, W-7, had no significant effects on either morphine-induced analgesia or the inhibitory actions of exposure to the magnetic fields. These results suggest that: (1) PKC has antagonistic effects on opiate-mediated analgesia in the snail, Cepaea, and (2) that the inhibitory effects of magnetic fields on opiate-induced analgesia involve alterations in PKC.

Inhibitory effects of 60-Hz magnetic fields on opiate-induced "analgesia" in the land snail, Cepaea nemoralis, under natural conditions

There is accumulating laboratory evidence that magnetic fields can affect a variety of opioid-mediated behavioral and physiological functions in both vertebrates and invertebrates. The present study examined the effects of various durations (0.50, 1.0 and 2.0 h) of exposure to a low intensity (1.0 gauss rms) 60-Hz magnetic field on opioid-mediated aversive thermal ("nociceptive") responses and morphine-induced "analgesia" in the land snail, Cepaea nemoralis, under natural environmental conditions. Exposure to the powerline-related 60-Hz magnetic fields significantly attenuated morphine-induced analgesia and the basal nociceptive responses of Cepaea, with the degree of attenuation being related to the duration of exposure to the magnetic fields. These results with Cepaea show that 60-Hz magnetic fields can affect opioid-mediated behavioral responses outside the laboratory under natural environmental conditions.

Endogenous opiates: 1989

This paper is the twelfth installment of our annual review of the research published during 1989 involving the behavioral, nonanalgesic, effects of the endogenous opiate peptides. The specific topics this year include stress; tolerance and dependence; eating; drinking; gastrointestinal and renal functions; mental illness; learning, memory, and reward; cardiovascular responses; respiration and thermoregulation; seizures and other neurological disorders; electrical-related activity; locomotor activity; sex, development, pregnancy, and aging; immunological responses; and other behavior.

Increased mortality in land snails (Cepaea nemoralis) exposed to powerline (60-Hz) magnetic fields and effects of the light-dark cycle

The effects of various durations (0.5, 2, 12, 48, or 120 h) of day- and night-time exposures to a 1.0 gauss (rms) 60-Hz magnetic field or sham field on mortality levels in the nocturnally-crepuscularly active land snail, Cepaea nemoralis, were examined. These snails were injected with morphine or saline vehicle and tested for reaction to an aversive thermal stimulus as part of another study. Mortality levels were monitored over a 2-week period following the initial exposure to the fields and were shown not to be differentially affected by the drug injection procedures. Mortality levels increased linearly as a function of increased length of exposure to the magnetic fields (P less than 0.001) but not when exposed to the sham fields. As well, night-time exposures resulted in greater mortality levels than day-time exposures (P less than 0.025). These results indicate that day-night rhythms are important in determining the magnitude of the magnetic field exposure effect. It is speculated that the magnetic fields may disrupt endogenous opioid- and calcium-modulated homeostatic mechanisms and augment stress effects, modifying a variety of systems including immunocompetence.

Day-night rhythms in the inhibitory effects of 60 Hz magnetic fields on opiate-mediated 'analgesic' behaviors of the land snail, Cepaea nemoralis

There is accumulating evidence that magnetic fields can affect a variety of opioid-mediated behavioral and physiological functions. The present experiments were designed to examine the effects of various durations of day- and night-time exposures to low intensity (1.0 gauss rms) 60 Hz magnetic fields on light (L) and dark (D) period opioid-mediated aversive thermal ('nociceptive') responses and morphine-induced 'analgesia' in the nocturnally-crepuscularly active land snail, Cepaea nemoralis. The snails displayed a LD rhythm in the latency of their aversive (40 degrees C) thermal (nociceptive) responses, showing a significantly greater response latency at night than during the day. Administration of morphine (10 mg/kg/2.0 microliters) elicited significant increases in the thermal response latencies indicative of the induction of analgesia. The snails displayed a significantly greater analgesic response at night than during the day. Exposure (0.50, 2, 12, 48 or 120 h in L or D) to the 60 Hz fields reduced morphine-induced analgesia in both the L and D periods, with the magnetic stimuli having significantly greater inhibitory effects in the D period. The magnetic fields also significantly attenuated the level of the dark period basal nociceptive response latencies, while not affecting the light period responses. In both the L and D periods the degree of attenuation of the analgesic and nociceptive response latencies was related to the duration of exposure to the 60 Hz magnetic fields.(ABSTRACT TRUNCATED AT 250 WORDS)

Magnetic fields inhibit opioid-mediated 'analgesic' behaviours of the terrestrial snail, Cepaea nemoralis

1. The terrestrial snail, Cepaea nemoralis, when placed on a warmed surface (40 degrees C) displays a thermal avoidance behaviour that entails an elevation of the anterior portion of the fully extended foot. The latency of this nociceptive response was increased by the prototypical mu and specific kappa opiate agonists, morphine and U-50, 488H, respectively, in a manner indicative of anti-nociception and the induction of 'analgesia'. Pretreatment with the prototypical opiate antagonist, naloxone, blocked the morphine- and reduced the U-50, 488H-induced analgesia. Naloxone had no effects on the thermal response latencies of saline treated animals. 2. Exposure to either cold (7 degrees C) or warm (38 degrees C) temperature stress increased the nociceptive thresholds of Cepaea in a manner indicative of the induction of 'stress-induced analgesia'. The warm stress-induced analgesia was opioid mediated, being blocked by naloxone, whereas, the cold stress-induced analgesia was insensitive to naloxone. 3. Exposure for 15-30 min to 0.5 Hz weak rotating magnetic fields (1.5-8.0 G) significantly reduced the analgesic effects of the mu and kappa opiate agonists in a manner similar to that observed with naloxone. The magnetic stimuli also inhibited the endogenous opioid mediated warm stress-induced analgesia and significantly reduced the cold stress-induced analgesia. The magnetic stimuli had no evident effects on the nociceptive responses of saline-treated animals. The dihydropyridine (DHP) and non-DHP calcium channel antagonists diltiazem, verapamil. and nifedipine differentially and significantly reduced, while the DHP calcium channel agonist, BAY K8644, significantly enhanced the inhibitory effects of the magnetic fields on morphine-induced analgesia.

Inhibitory effects of acute exposure to low-intensity 60-Hz magnetic fields on electrically kindled seizures in rats

The possibility that exposure to power-line frequency (60-Hz) magnetic fields might affect the development or characteristics of epileptic seizures in electrically kindled rats, was examined. Male adult rats with electrodes implanted in the basolateral amygdala were exposed to either a 60-Hz, 1.0 gauss magnetic field or to a sham field condition for 1 h prior to each daily brain stimulation session. EEG recordings were made to measure afterdischarge characteristics after each daily brain stimulation. Once the animals exhibited a full stage 5 seizure (after approximately 12-15 stimulations) a cross-over manipulation was used. On the last test day the sham field control group was exposed to the 60-Hz magnetic field for 1 h prior to brain stimulation and the experimental group, normally exposed to the magnetic fields, was exposed to the sham field condition. Examination of afterdischarge durations revealed a weak retardation in the development of kindling in the experimental group (P = 0.08). In the cross-over test, exposure to the 60-Hz magnetic fields resulted in a significant (P = 0.019) inhibition in afterdischarge duration relative to the rats exposed to the sham field conditions. These results clearly suggest an inhibitory effect of acute exposure to low intensity 60-Hz magnetic fields on the duration of afterdischarges in electrically kindled rats. Possible mechanisms for such an effect are discussed.

Day-night rhythms of opioid and non-opioid stress-induced analgesia: differential inhibitory effects of exposure to magnetic fields

Day-night rhythms occurred in the naloxone-reversible (1.0 mg/kg), warm (opioid) and naloxone-insensitive, cold (non-opioid) swim stress-induced analgesia displayed by CF-1 mice. Maximum antinociceptive responses were evident at night, with the cold stress having significantly greater day- and night-time analgesic effects than the warm stress. An exposure for 30 min to a 0.5 Hz rotating magnetic field (1.5-90 gauss) reduced both the warm and cold stress-induced analgesia, with the magnetic stimuli having significantly greater inhibitory effects at night and on the opioid-induced responses. These results indicate that exposure to oscillating magnetic fields can significantly, and differentially, alter both opioid and non-opioid stress-induced analgesia and their day-night rhythms.

Morphine-induced analgesia and exposure to low-intensity 60-Hz magnetic fields: inhibition of nocturnal analgesia in mice is a function of magnetic field intensity

In 2 experiments male CF-1 mice were exposed for 60 min, during the mid-dark period of the day-night cycle, to low-intensity (0.5-1.5 gauss, rms) 60-Hz magnetic fields and then tested for levels of analgesia induced by morphine (10 mg/kg) injections. The magnetic field exposures inhibited the degree of morphine-induced analgesia in a field intensity-dependent manner in both experiments (P less than 0.01) with the largest inhibitory effect after exposure to the 1.5-gauss field. Analysis of the combined data from the two experiments revealed a significant (P less than 0.001) linear relationship between level of analgesia and magnetic field intensity. Thus, these data demonstrated a functional relationship between the behavioral effects of morphine in mice and the strength of the 60-Hz magnetic field. Possible mechanisms underlying these effects are discussed.