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Electromagnetic Biology and Medicine
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Effect of electromagnetic field on cyclic adenosine
monophosphate (cAMP) in a human mu-opioid
receptor cell model
Christina L. Ross, Thaleia Teli & Benjamin S. Harrison
To cite this article: Christina L. Ross, Thaleia Teli & Benjamin S. Harrison (2015):
Effect of electromagnetic field on cyclic adenosine monophosphate (cAMP) in a
human mu-opioid receptor cell model, Electromagnetic Biology and Medicine, DOI:
10.3109/15368378.2015.1043556
To link to this article: http://dx.doi.org/10.3109/15368378.2015.1043556
Published online: 29 Dec 2015.
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ORIGINAL ARTICLE
Effect of electromagnetic field on cyclic adenosine monophosphate (cAMP)
in a human mu-opioid receptor cell model
Christina L. Rossa,b
, Thaleia Telia
, and Benjamin S. Harrisona
a
Wake Forest Institute for Regenerative Medicine, Wake Forest Baptist Health, Winston-Salem, NC, USA; b
Wake Forest Center for Integrative
Medicine, Wake Forest Baptist Health, Winston-Salem, NC, USA
ABSTRACT
During the cell communication process, endogenous and exogenous signaling affect normal as
well as pathological developmental conditions. Exogenous influences such as extra-low-frequency
electromagnetic field (EMF) have been shown to effect pain and inflammation by modulating G-
protein receptors, down-regulating cyclooxygenase-2 activity, and affecting the calcium/calmo-
dulin/nitric oxide pathway. Investigators have reported changes in opioid receptors and second
messengers, such as cyclic adenosine monophosphate (cAMP), in opiate tolerance and depen-
dence by showing how repeated exposure to morphine decreases adenylate cyclase activity
causing cAMP to return to control levels in the tolerant state, and increase above control levels
during withdrawal. Resonance responses to biological systems using exogenous EMF signals
suggest that frequency response characteristics of the target can determine the EMF biological
response. In our past research we found significant down regulation of inflammatory markers
tumor necrosis factor alpha (TNF-α) and nuclear factor kappa B (NFκB) using 5 Hz EMF frequency.
In this study cAMP was stimulated in Chinese Hamster Ovary (CHO) cells transfected with human
mu-opioid receptors, then exposed to 5 Hz EMF, and outcomes were compared with morphine
treatment. Results showed a 23% greater inhibition of cAMP-treating cells with EMF than with
morphine. In order to test our results for frequency specific effects, we ran identical experiments
using 13 Hz EMF, which produced results similar to controls. This study suggests the use of EMF as
a complementary or alternative treatment to morphine that could both reduce pain and enhance
patient quality of life without the side-effects of opiates.
ARTICLE HISTORY
Received 31 October 2014
Revised 2 March 2015
Accepted 12 April 2015
Published online 7 July 2015
KEYWORDS
Inflammatory pain;
low-frequency EMF; cyclic
adenosine monophosphate
(cAMP); G-protein coupling
receptors (GPCRs);
mu-opioid receptors
Introduction
Tissue injury results in the production of inflammatory
mediators, several of which sensitize primary afferent
nociceptors (Davis et al., 1993; Reuff and Dray, 1993),
resulting in hyperalgesic pain (Ferreira, 1981; Fierreira
et al., 1978). Hyperalgesic pain is often associated with
inflammatory pain (Schultz et al., 2003). The largest
family of receptors for pharmaceutical agents is the
G-protein-coupled receptors (GPCRs), whose signal
transduction pathway is well understood. For example,
Gαs (stimulating) subunit increases adenylate cyclase
(AC) activity, thereby stimulating the production of
cyclic adenosine monophosphate (cAMP); whereas the
Gαi (inhibitory) subunit decreases AC activity and inhi-
bits the production of cAMP. The second messenger
cAMP activates a specific number of tissue-specific
cAMP-dependent protein kinases, ultimately affecting
intracellular processes such as ion channel activity,
release of neurotransmitters, regulation of transcription
factors, and numerous other processes. GPCRs
determine ligand binding and selectivity (Karlsmark
et al., 2003). A number of ligands inhibit the function
of specific enzymes by competitive or non-competitive
inhibition (Sen et al., 2009). A ligand that binds to the
same active catalytic site as the endogenous substrate is a
competitive inhibitor. Ligands that bind at different sites
on the enzyme, alter the shape of the molecule, and
reduce its catalytic activity, are called non-competitive
inhibitors. Extracellular environments, and to some
extent transmembrane regions, determine ligand bind-
ing (Brenner and Steven, 2010). A substantial amount of
literature suggest that hyperalgesia induced by tissue
damage is initiated by the activation of AC – cAMP –
protein kinase A (PKA) second messenger cascade, acti-
vated at the mu-opioid receptor (MOR) site (England
et al., 1996; Khasar et al., 1995; Malmberg et al., 1997;
Taiwo and Levine, 1989, 1990, 1991, 1992). Agents that
inhibit AC- and cAMP-dependent PKA prevent induc-
tion of hyperalgesia by prostaglandin E2 (PGE2) and
other inflammatory mediators.
CONTACT Christina L. Ross chrross@wakehealth.edu Wake Forest Institute for Regenerative Medicine, Wake Forest Baptist Health, Winston-Salem,
NC 27109, USA.
ELECTROMAGNETIC BIOLOGY AND MEDICINE
http://dx.doi.org/10.3109/15368378.2015.1043556
© 2015 Taylor & Francis
Downloadedby[ChristinaRoss]at11:2130December2015

Cyclic AMP is required for cell communication in
the hypothalamus/pituitary gland axis and for the feed-
back control of hormones of the sympathetic nervous
system (SNS) (Vargas et al., 2001). It is synthesized
from adenosine triphosphate (ATP) by adenylyl cyclase
(AC) located on the inside of the cell membrane, and is
an important signal carrier necessary for the proper
biological response of cells to hormones and other
extracellular signals that initiate inflammatory pain
through the cAMP response element binding (CREB)
protein cycle. Cyclic AMP is activated by a range of
signaling molecules via AC stimulatory G-protein (Gs)-
coupled receptors and inhibited by agonists of AC
inhibitory GPCRs (Gi) (Billington and Penn, 2003;
Khoury et al., 2014). GPCRs also form homo- and/or
hetero-dimers, and their impact on receptor physiology
and pharmacology has attracted a lot of interest (CRR,
2013). Data suggest that the MOR is a heterodimer that
heterodimerizes only at the cell surface, and the oligo-
mers of opioid receptors and heterotimeric G-proteins
are the bases for MOR heterodimer phenotypes
(Markova and Mostow, 2012). There is accumulating
evidence that oligomerization of GPCRs can alter the
selectivity and affinity of ligand binding, and this has
been reported for opioid receptor heterodimers
(Andreadis and Geer, 2006; Gurtner et al., 2008). Due
to this phenomenon an alteration in binding properties
could sensitize receptors to ligands, thereby allowing
responses to lower agonist concentrations. Receptor
dimerization can also result in the formation of novel
binding sites. There are many documented examples of
interactions between GPCRs coupling preferentially to
different signaling pathways, which result in a potentia-
tion of Ca2+
signaling (Fiorotto and Klish, 1991;
Gourevitch et al., 2014). GPCRs are components of
multi-protein signaling complexes that regulate the
localization and function of receptors which form com-
plexes with a wide variety of signaling and regulatory
proteins. For these experiments we have chosen the
mu-opioid receptor as our target, because it is most
associated with potent analgesics currently used to con-
trol pain (Tzschentke et al., 2014).
Opioid dependence has been reported to be asso-
ciated with changes in the cAMP systems in experi-
ments in vitro. For example, in neuroblastoma cells,
acute treatments with morphine and other opiates inhi-
bit adenylate cyclase (AC) activity resulting in a
decrease of cAMP levels (Sharma et al., 1975; Traber
et al., 1975); however, after repeated exposure to mor-
phine, the AC activity and cAMP levels return to con-
trol levels in the tolerant state and increased above
control levels during withdrawal (Benalal and
Bachrach, 1985; Sharma et al., 1975; Traber et al.,
1975). These findings are the basis for cAMP as the
mechanism of action for the development of morphine
dependence (Mamiya et al., 2001). An increase in AC
activity and cAMP levels in the brain represent bio-
chemical associations of morphine dependence (Collier,
1980; Kuriyama et al., 1978), whereby cAMP levels are
regulated by AC and phosphodiesterases (PDEs)
(Thompson, 1991). It has been substantiated that 3-
isobutyl-1-methylxanthine (IBMX)-modulated forsko-
lin induces behavior that resembles morphine
withdrawal syndrome in naïve rats and increases nalox-
one-precipitated morphine withdrawal syndrome in
morphine dependent rats (Collier and Francis, 1975;
Rasmussen et al., 1990).
In humans, electromagnetic field (EMF) therapy has
proven to be a safe, non-invasive, easy-to-use method
to treat the source of pain and inflammation (Markov,
2007; Ross and Harrison, 2013). Research has shown
that therapeutic applications at extra-low frequency
(ELF) EMF (1–100 Hz) levels stimulate the immune
system by suppressing inflammatory responses at the
cell-membrane level (O’Connor et al., 1990). Double-
blind, placebo-controlled clinical trials (Stiller et al.,
1992) report EMF passes through the skin into the
body’s conductive tissue (Hannan et al., 1994; Stiller
et al., 1992; Traina et al., 1998), reducing pain and the
onset of edema shortly after trauma (Chalidis et al.,
2011; Rohde et al., 2009). In one such study low-
frequency pulsed EMF (PEMF) therapy at 0.1 to 64
Hz was reported to improve mobility, and reduce pain
and fatigue in fibromyalgia patients (Sutbeyaz et al.,
2009). Both human and in vitro studies report EMF to
be effective in the treatment of pain and inflammation
in osteoarthritis (OA) (Li et al., 2013; Sadoghi et al.,
2013), without the addictive side-effects of opiates. It
has been proposed that charge receptors or other kinds
of sensors at the extracellular membrane could recog-
nize EMF by their ability to resonate with varying
frequencies (Funk and Monsees, 2006).
In this study we hypothesize that an EMF at certain
frequencies can be therapeutic, therefore we are looking
for a similar down regulatory effect of EMF on cAMP
as would be seen in morphine treatment. EMF has a
number of well-documented therapeutic effects on cells
and tissues afflicted with inflammatory pain (Ross and
Harrison, 2013). Reports of resonance frequency
responses of biological systems to exogenous EMF sig-
nals suggest the frequency response characteristics of
the tissue can determine the EMF response (Bawin
et al., 1975; Markov, 1981). EMF parameters such as
frequency, field strength, and time of exposure, all
account for the mechanistic pathway affecting inflam-
matory pain mediators. Oscillating EMF exerts forces
2 C. L. ROSS ET AL.

on free ions present on both sides of the plasma mem-
brane which move across the cell surface through the
transmembrane proteins creating a forced intracellular
vibration. This force is responsible for phenomena such
as the influx of extracellular calcium and the binding
affinity of calmodulin (CaM) – the primary transduc-
tion pathway to second messengers such as cAMP.
Because of the important ramifications for treating
inflammatory pain, we investigated the effect of EMF
on the cAMP second messenger pathway, which con-
tributes to maintenance as well as the initiation of
hyperalgesia.
Materials and methods
A Chinese Hamster Ovary (CHO-K1) cell line trans-
fected with human mu(µ)-opioid receptors (catalog
#6605, ChanTest Corp, Cleveland, OH) was cultured
in flasks using Ham’s F-12 1X modified media with L-
glutamine (Mediatech, Inc., Manassas, VA); 10% FBS,
1% non-essential amino acids (100X, #11140-050,
Gibco, Grand Island, NY); 0.4 mg/ml Geneticin
(G418, #10131-027, Gibco, Grand Island, NY); and
1% penicillin-streptomycin (Cellgro#30-002-CL, Fisher
Scientific, Pittsburg, PA), then incubated in 5% CO2 at
37 °C and 100% humidity until ∼80% confluent. Cells
were detached from flasks using trypsin, then centri-
fuged at 1500 rpm for 5 min and reseeded in two sepa-
rate 6-well culture plates (treatment and control) at a
density of 2.5 × 105
cells/mL.
Stimulation of cAMP
Cyclic AMP was stimulated by exposing µ-CHO cells
to 10µM forskolin (Sigma #F6886, St. Louis, MO).
Forskolin is a labdane diterpene produced by the
Indian coleus plant, and is commonly used in medical
research to raise cAMP levels (Gris et al., 2010).
Forskolin re-sensitizes cell receptors by activating ade-
nylyl cyclase (AC) to catalyze the levels of cAMP. Cells
were also stimulated with 0.5 mM 3-isobutyl-1-
methylxanthin (IBMX, Sigma #17018, St. Louis,
MO), which is a phosphodiesterase inhibitor that will
prevent the degradation of the phosphodiester bond in
the second messenger molecule cAMP. All stimulation
times were 15 min as is standard for this protocol (Xu
et al., 2003). Duplicate experiments were performed
on CHO-K1 cells used as negative control. Outcomes
were measured based on EC50 or half maximal effec-
tive concentration of the morphine (CatchPoint
Cyclic-AMP Fluorescent Assay Kit #R8088,
Molecular Devices, Sunnyvale, CA).
Experimental groups
Six individual groups were used in this experiment: (1)
µ-CHO cells only (baseline) [positive control]; (2)
µ-CHO cells + forskolin/IBMX stimulant [F only]; (3)
µ-CHO cells + forskolin/IBMX stimulant + 0.1 mM
morphine [F + M]; (4) µ-CHO cells + forskolin/IBMX
stimulant + EMF treatment [F + E]; (5) µ-CHO cells +
forskolin/IBMX stimulant + 0.1 mM morphine + EMF
treatment [F + M + E]; and (6) CHO-K1 [negative con-
trol]. In the F + M + EMF group, morphine was added
immediately before cells were exposed to EMF.
PEMF exposure
Using a commercially manufactured 11-inch diameter
Helmholtz Coil (SpinCoil-11-X, Micro Magnetics, Fall
River, MA), both µ-CHO cells and CHO-K1 cell groups
underwent the same experimental conditions. The [F +
E] and [F + M + E] groups were exposed to a 5 Hz EMF
for 15 min to determine treatment effect on cAMP. The
time point of 15 min was selected as it is the amount of
time needed for cAMP accumulation levels to be main-
tained fully until the end of the incubation period. The
EMF coils were driven by an alternating current power
supply with adjustable frequency and amplitude. From
the coil center the uniform field strength was measured
to be approximately 1.5 µT (see flux density schematic
in Figure 1a). Each coil carried a 50% duty sine wave in
the same direction (Figure 1b). The EMF was charac-
terized using a Gauss meter (Sypris Model 5180; Pacific
Scientific-OECO, Milwaukie, OR). The frequency was
quantified using an oscilloscope (Model TDS 20248;
Tektronix Inc, Beaverton, OR). Experiments were per-
formed under ambient conditions. After exposure to
EMF, a live/dead cell assay was performed using calcein
acetomethoxy (catalog # C697959; Life Technologies,
Carlsbad, CA), showing no significant change in cell
viability (data not shown). Measurements were taken
using a Spectramax M5 plate reader (Molecular Devices
LLC, Sunnyvale, CA), at 530 nm excitation level and
590 nm emission level. Control samples were kept in
the same conditions without exposure to EMF. The
EMF exposed cells were kept in a warm bath to ensure
a consistent 37 °C temperature during these experi-
ments. Background EMF was measured and averaged
the same as Earth’s (∼0.5 Gauss).
Statistical analysis
All data measured are presented as mean ± standard
error of the mean (S.E.M.), for n = 4 samples. For all
assays, a one-way analysis of variance (ANOVA) with
ELECTROMAGNETIC BIOLOGY AND MEDICINE 3

Tukey’s post hoc test was used to assess the differences
between the controls and the cells exposed to the EMF,
with p < 0.05 considered statistically significant for all
tests.
Results
The aim of this study was to investigate the effect of a
low-frequency EMF on cAMP, which is a second mes-
senger transcription factor used for intracellular signal
transduction on the AC-cAMP-PKA-dependent path-
way. This pathway contributes to the initiation and
maintenance of hyperalgesia. In this experiment we
have chosen to study the human mu (µ) opioid receptor
in particular because it belongs to the GPCR super
family of receptors whose activation leads to a cascade
of events that inhibit AC and decrease cAMP levels,
and also has a strong binding affinity with morphine
(Osugi et al., 1996). Using n = 4 samples for three trials,
we compared the results of an EMF treatment with that
of morphine. Since the opiate receptor ligand morphine
has a considerably higher binding affinity for mu-
opioid receptors (MORs) than for other opioid recep-
tors, and its occupation can inhibit AC and cAMP
formation, we hypothesized the EMF would affect the
binding affinity of the MORs. What we found was that
a statistically significant inhibition of cAMP did indeed
occur in the EMF-exposed cells. EMF exposure on the
MOR transfected cells reduced the amount of cAMP by
23% more as compared with the morphine-treated
sample. CHO-K1 cell line produced results similar to
basal (baseline) (Figure 2).
In the experimental group where MORs stimulated
with forskolin increased cAMP levels, which were
exposed to 5 Hz EMF [F + EMF], there was a
statistically significant (p < 0.05 for n = 4 samples)
decrease in cAMP levels (Figure 3). After finding an
inhibitory effect of EMF on cAMP at 5 Hz, we wanted
to compare it with a different frequency in order to
determine if the effect was frequency dependent.
Therefore, we duplicated the experiment using 13 Hz
to compare with the outcome of the 5 Hz treatment.
This number was chosen due to the lack of published
evidence of any therapeutic value related to its fre-
quency. As shown in Figure 2, the effect of EMF on
mu-cells was more inhibitive at 5 Hz than at 13 Hz
(Figure 2a and c). While we hypothesized that EMF
would improve the efficacy of morphine, this did not
appear to be the case.
Data represent standard error of mean (S.E.M.). A
statistically significant difference (p < 0.05) between
morphine and EMF [F + M vs. F + EMF and F + M vs.
F + M + EMF] was observed in cells exposed to 5 Hz
frequency, but not between EMF and morphine com-
bined [EMF + F vs. EMF + F + M]. EMF does not
appear to counteract the inhibition potential of
morphine.
Discussion
Pain killers target membrane transport proteins,
including ligand- and voltage-gated ion channels. At
ligand-gated ion channels, drugs can bind at the
same site as the endogenous ligand and directly
compete for the receptor site. Although membrane
ion channels and protein phosphorylation can be
indirectly affected by GPCRs through effector pro-
teins such as AC and second messengers such as
cAMP, they can short circuit the second messenger
pathway and gate the ion channels directly (Brown
Figure 1. (A) Schematic representation of Helmholtz coil shows radius of 11″ coils equals the distance separated; (B) oscilloscope
graticule shows 5 Hz pulsed waveform.
4 C. L. ROSS ET AL.

et al., 1988). This bypassing of the second messenger
pathway is observed in mammalian cardiac myocytes
where Ca2+
channels are able to survive and function
in the absence of cAMP, ATP, or protein kinase C
(PKC), when in the presence of the activated α-
subunit of the G protein (Yatani et al., 1987). Here
Gα, which is stimulatory to AC, acts on the Ca2+
channel directly as an effector. This short circuit is
membrane-delimited, allowing direct gating of Ca2+
channels by G-proteins to produce effects more
quickly than the cAMP cascade could (Brown et al.,
1988). Some drugs directly bind and inactivate vol-
tage-gated ion channels; these are ion channel pro-
teins that do not have endogenous ligands, but open
or close as a function of the membrane voltage
potential. This membrane voltage potential has been
suggested as the mechanism of action for the biolo-
gical effect of EMF through the plasma membrane
(Adey, 1974; Liboff, 1985; McLeod et al., 1987) –
across which the EMF signal induces a voltage
change (Figure 4).
Oscillating EMF exerts forces on free ions present on
both sides of the plasma membrane that move across
the cell surface through transmembrane proteins, creat-
ing a forced intracellular vibration. This vibration is
responsible for phenomena such as the influx of extra-
cellular Ca2+
, as well as efflux of intracellular Ca2+
. A
rise in cytosolic Ca2+
concentration is used as a
cAMP_Mu cells_5Hz
Basal
Fonly
F+
M
F+
EM
F
F+
M
+
EM
F
Basal
Fonly
F+
M
F+
EM
F
F+
M
+
EM
F
Basal
Fonly
F+
M
F+
EM
FF+
M
+
EM
F
Basal
Fonly
F+
M
F+
EM
F
F+
M
+
EM
F
0
20
40
60
Fluorescence(RDU)
*
cAMP_CHO-K1_5Hz
0
20
40
60
Fluorescence(RDU)
cAMP_mu-CHO_13 Hz
0
20
40
60
Fluorescence(RDU)
cAMP_CHO-K1_13Hz
0
20
40
60
(a) (b)
(c) (d)
Fluorescence(RDU)
Figure 2. (a) CHO cells transfected with MORs significantly up-regulate forskolin stimulated cAMP was inhibited at 5 Hz. One-way
ANOVA shows significant difference between morphine and EMF [F + M vs. F + EMF]; (b) Blank CHO cells (K1 – not transfected)
stimulated with forskolin neither significantly up-regulated cAMP, nor significantly inhibited cAMP after treatment with 5 Hz EMF;
(c) while 13 Hz EMF exposure showed significant down-regulation of forskolin-stimulated cAMP [F only vs. F + EMF], there was no
significant difference between the morphine and EMF treatment [F + M vs. F + EMF], compared with EMF exposure at 5 Hz;
(d) CHO-K1 cells did not significantly respond to either the forskolin or the EMF.
1%
91%
41%
18% 21%
−40%
−20%
0%
20%
40%
60%
80%
100%
120%
B F only M only EMF + F EMF + F + M
PercentDifference
cAMP (nM)
Figure 3. Percentage comparison of MORs stimulated with for-
skolin to upregulate cAMP showed significant inhibition of
cAMP after treatment with both morphine [F + M] and mor-
phine combined with EMF [F + M + EMF] at 5 Hz EMF.

signaling messenger in nearly all eukaryotic cells
(Berridge et al., 2000; Clapham, 2008). Oscillations in
cytosolic Ca2+
concentration are observed in all cell
types, suggesting they represent a universal signaling
mode (Thomas et al., 1996). Changes in the plasma
membrane potential can alter the activity of voltage-
gated Ca2+
channels leading to bursts of Ca2+
entry
(Parekh, 2011), which can result directly in Ca2+
oscil-
lations which can trigger second messengers through
the activation of cell-surface receptors that activate
enzymes such as AC, modulator of cAMP. Regardless
of the mechanism, oscillations in cytosolic Ca2+
con-
centration can be supported for a few minutes in the
absence of external Ca2+
, showing that Ca2+
recycling
across the intracellular stores is the primary mechanism
for driving them (Parekh, 2011). Oscillation triggered
in Ca2+
-free solution does decrease with time, because a
fraction of the Ca2+
released during each cycle is trans-
ported out of the cell, causing less Ca2+
to be available
to support the next oscillation. To sustain oscillation
requires Ca2+
entry, and this is accomplished through
Ca2+
channels in the plasma membrane (Parekh, 2010;
Parekh and Putney, 2005).
EMF has also been reported to be instrumental in
the binding affinity of calmodulin (CaM) – the primary
transduction pathway to second messengers cAMP, and
cyclic guanosine monophosphate (cGMP), found to
influence inflammatory pain (Pilla et al., 2011). Since
EMF decreased the amount of cAMP by 23% compared
with morphine, it is either causing a change in the
conformation of the GPCRs, or it is affecting the sec-
ond messenger cAMP via the voltage-gated calcium
channels (VGCCs). This action could be achieved
through several high thresholds, slowly activating Ca2+
channels in neurons which are regulated by G-proteins
(Morris and Malbon, 1999). The activation of
α-subunits of G-proteins has been shown to cause
rapid closing of voltage-dependent Ca2+
channels,
which causes difficulties in the firing of action poten-
tials (Stryer et al., 2007). This inhibition of voltage-
gated Ca2+
channels by GPCRs has been demonstrated
in the dorsal root ganglion of a chick and other cells
lines (Morris and Malbon, 1999). Other studies have
indicated roles for Gα subunits in the inhibition of Ca2+
channels (Jeon et al., 2013; Zhang et al., 2008). Since
receptors normally pick up signals in the cells’ environ-
ment, and G-proteins couple these signals to the effec-
tors (sending the signal to the cytoplasm), it is feasible
that the EMF was able to short circuit the second
messenger pathway and gate the ion channels directly.
This would account for a moderately stronger down-
regulation of cAMP with EMF treatment than with
morphine.
Conclusion
The therapeutic effects of low-frequency EMF have
been reported for years; however, a mechanism of
action has yet to be elucidated. Here we compared the
effects of EMF on cAMP at both 5 Hz and 13 Hz. The 5
Hz frequency showed a stronger inhibitory effect in
cAMP expression on [F + EMF] than the 13 Hz fre-
quency. EMF appears to competitively inhibit cAMP
as morphine does; however, EMF exposure does not
have the addictive side-effects of morphine. If EMF
changes the conformation of the MOR receptor, along
with stabilizing Ca2+
flux, then it would explain the
outcomes we observed. If EMF is able to induce
Non-conductive medium =
~3nm insulating membrane
Polarized membrane Depolarized membrane
Ca2+ ions ns
Ca2+ ions
EF = -Q
(a) Voltage-gated ion channel prior to
application of EMF
(b) Voltage-gated ion channel after
application of EF or EMF
Figure 4. (a) Voltage-gated ion channels control intra-
and extra-
cellular ion flux due to positive surface charge. (b) EF can attenuate
the opening and closing of these ion channels to trigger intracellular events due to negative charge (-
Q) depolarizing the plasma
membrane.
6 C. L. ROSS ET AL.

homeostasis via the stabilization of Ca2+
, then it
appears to be frequency specific as our study suggests.
Declaration of interest
The authors wish to thank the Guth Endowment Fund for
providing financial support for this project (120-330-740196).
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8 C. L. ROSS ET AL.

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