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differential
localization
ELECTROPHYSIOLOGICAL
RESEARCH ON THE DIFFERENTIAL LOCALIZATION OF AURICULAR ACUPUNCTURE POINTS
Terry Oleson, PhD
ABSTRACT
Neurophysiological
studies have examined the theoretical work of Dr Paul Nogier regarding
differential correspondence of internal visceral disorders to the central
concha of the ear, musculoskeletal problems to the surrounding antihelix
on the auricle, and neurological pain to the outer helix of the ear.
Double-blind studies of auricular diagnosis have shown that specific
areas of Nogier's antihelix auricular zone correspond to the actual
area of musculoskeletal pain, while coronary problems were identified
by bioelectrically reactive auricular reflex points in the central concha
of the ear. Animal investigations have demonstrated that stimulation
of the stomach tissue led to the development of low resistance points
on the concha of the ear, whereas stimulation of the concha points themselves
led to differential activation of firing patterns in hypothalamic neurons.
When animals were tested for threshold to tooth shock pain, stimulation
of the auricular point for the trigerninal nerve led to an elevation
of pain threshold and a reduction of brain-evoked potentials. Research
demonstrating release of endorphins by stimulation of auricular acupuncture
points provides a neurobiological basis for the clinical actions of
auricular acupuncture.
KEY WORDS
Auricular
Acupuncture, Nogier Embryological Zones, Musculoskeletal Pain, Visceral
Disorders, Neurophysiological Recordings
Introduction
A previous article in Medical Acupuncture1
examined the clinical application of treating different zones on the
external ear for relieving varying types of pain. The opportunity to
examine the electrophysiological research that supports clinical studies
of auricular acupuncture was recently provided at an international scientific
symposium ("New Directions in the Scientific Exploration of Acupuncture,"
May 1999, University of California, Irvine). The findings by Cho et
al2 that differential changes
in functional magnetic resonance images (MRI) of the brain are selectively
activated by stimulating different acupuncture points has initiated
renewed interest in understanding the neurophysiological mechanisms
for acupuncture. The inverted fetus, somatotopic perspective of the
external ear, has been principally derived from clinical experiences
in conducting auricular acupuncture with patients in China3
and Europe.4 There is now an
accumulation of scientific studies examining electrophysiological data
obtained from animals and humans that provide neurobiological support
for these clinical findings.5
Different anatomical regions of the external
ear are shown in Figure 1,
whereas the specific functional zones of the ear
are represented in Figure 2. The central concha
of the ear is innervated by the vagus nerve and is thought to serve
as the region for autonomic regulation of pain and pathology originating
from internal organs. The surrounding antihelix and antitragus ridges
of the ear represent somatic nerve processing of myofascial pain, backaches,
and headaches. The outer helix tail and earlobe represent the spinal
cord and brain regions, which are reported to affect neuropathic pain
such as peripheral neuropathies and trigerninal neuralgia. The body
organs represented on the external ear can be viewed as 3 concentric
rings. According to Nogier,6
the embryologicallybased endodermal organs are found at the center of
the ear, the mesodermal tissue that becomes the somatic musculature
is represented on the middle ridges of the auricle, and the ectodermal
skin and nervous system tissue are found on the outer ridges of the
ear. Each of these 3 auricular regions depicts body orientation in an
inverted somatotopic pattern. Higher organs of the actual lungs, shoulder,
or cerebral cortex are represented on lower areas of the auricle; lower
organs of the actual intestines, leg, or lumbar spinal cord are represented
on higher areas of the auricle (Fig.
3).
 Neurophysiological
Theories of Acupuncture and Microacupuncture Systems
The author has previously proposed7
that the relief of pain by auricular acupuncture can be best understood
by the theory of stimulation-produced analgesia. Liebeskind et al8
developed this theory to account for the pain-relieving effects following
electrical stimulation of neurons in the brain. In addition to the classicallyknown,
ascending, pain-sensation pathway, there is a descending, pain-inhibitory
pathway. The pain-inhibitory system travels from the brainstem, down
the spinal cord, then activates pain-suppressive neurons in the dorsal
horn of the spinal cord. In their gate control theory of pain, Melzack
and Wall9 focused on the inhibition
of input from nociceptive neurons by input from tactile neurons interacting
through spinal cord interneurons. However, they further allowed that
supraspinal gates in the brain could produce descending messages to
these same inhibitory interneurons, thus blocking the ascending pain
signal.
Basbaum and Fields10 showed
that lesions in the descending, dorsolateral funiculus tract in the
spinal cord blocked behavioral analgesia from deep brain stimulation.
There is both a descending pain facilitation system and a descending
pain-inhibition system in the central nervous system, comparable to
the Yin and Yang of Taoist theory. Wei et al11
have shown that destruction of both descending, serotonergic, raphe
pathways, and descending, noradrenergic, locus coeruleus pathways leads
to an increase in the fos protein activity of nociceptive spinal neurons.
Conversely, destruction of descending, reticular, gigantocellular pathways
leads to a decrease in the fos protein activity of nociceptive spinal
neurons. The pain-inhibition system was selectively damaged by the raphe
and locus coeruleus lesions, whereas the pain-facilitation system was
disconnected by the reticular lesion. Acupuncture may also utilize this
pain inhibitory system.12
The most potent area for obtaining stimulation-produced
analgesia in rats was the midbrain periaqueductal gray,8
a region with neurons specifically responsive to noxious stimuli. Research
in primates" has shown that deep brain stimulation in the subcortical
thalamus is a more potent site for creating stimulation-produced analgesia
in higher species. Examination of deep brain stimulation in humans has
shown similar findings.14
Research also has confirmed that nociceptive pain messages activate
positron emission tomographic (PET) scan activity in the periaqueductal
gray, thalamus, hypothalamus, somatosensory cortex, and prefrontal cortex
regions of humans;15 included
is the same brainstern and thalamic areas that are able to suppress
pain messages. While direct connections between auricular acupuncture
points and these antinociceptive brain pathways have not yet been investigated,
neurophysiological investigations of body acupuncture points suggest
that the regions of the brain related to pain inhibition are also affected
by the stimulation of acupoints.16
According to Dale,17
the holographic homunculus pattern shown on the external ear is one
of several microacupuncture systems that connect peripheral regions
of the body to the central nervous system (CNS). Dale hypothesized that
ear acupoints have remote reflex connections to other parts of the body
through neuronal pathways in the CNS. Dale proposed that there are both
organo-cutaneous reflexes that allow the microsystern to reveal underlying
body pathology and cutaneo-organic reflexes that enable microacupuncture
stimulation to heal the pathological condition. Foot reflexology, hand
acupuncture, and scalp acupuncture are other examples of such microacupuncture
systems, each serving as peripheral terminals in the body that connect
to a central brain computer.7
Lee has developed a thalamic neuron theory
to account for reflex connections between acupuncture points and the
brain.18,19
Pathological changes in peripheral tissue will eventually lead to firing
pattems in corresponding neural microcircuits in the brain and spinal
cord. The organization of the connections between peripheral nerves
and the CNS is controlled by sites in the sensory thalamus that are
arranged like a homunculus. The CNS institutes corrective measures intended
to normalize the disordered neural circuits; strong environmental stressors
or intense emotions may cause the CNS circuitry to malfunction. If the
neurophysiological programs in the neural circuits are impaired, the
peripheral disease may remain chronic. Thus, pain and disease are attributed
to learned, maladaptive programming of these dysfunctional neural circuits.
Stimulation of acupuncture points on the body or ear can serve to induce
a reorganization of these pathological brain pathways. The spatial arrangement
of these neuronal chains within the thalamic homunculus is said to account
for the arrangement of acupuncture meridians in the periphery. The invisible
meridians that purportedly run over the surface of the body may actually
be due to nerve pathways projected onto neuronal chains in the thalamus.
The auricular acupuncture system is more noticeably arranged in a somatotopic
pattern on the skin surface of the external ear.
There have
been 4 main thrusts in acupuncture research designed to examine these
neurophysiological theories. First, whether the existence of auricular
and body acupuncture reflex points can be substantiated by electrophysiological
measures. Second, whether the areas of the brain associated with stimulation-produced
analgesia also are affected by the stimulation of acupuncture points.
Third, whether changes in the natural opiates, the endorphins and enkephalins,
reliably account for the pain-relieving effects of auriculotherapy and
body acupuncture. Finally, whether there is evidence that the sornatotopic
pattern described for the auricle is specifically associated with changes
in neural activity in different parts of the brain.
Electrodermal Determination of Acupuncture
Points
The first double-blind assessment to scientifically
validate the somatotopic pattern of reflex points on the auricle was
conducted by the author and his colleagues.20
Forty patients with specific musculoskeletal pain were first evaluated
by a physician or nurse to determine the exact location of their physical
pain. They were then draped with a sheet so that only their external
ear was exposed. Crutches and braces were removed from the room to prevent
any clues as to the nature of their condition. A second physician who
had extensive training in auricular acupuncture procedures then examined
each patient's ear. This second physician had no prior knowledge of
the subject's previously established medical diagnosis and was not allowed
to verbally interact with the patient. Auricular diagnosis was determined
by numerically-rated levels of tenderness to a palpating probe and by
the quantified electrical conductivity of the skin. Specific areas of
the auricle were examined that corresponded to different musculoskeletal
regions of the body. There was a positive correspondence between auricular
points identified as reactive, both tender to palpation and exhibiting
at least 50 uA of electrical conductivity, and the parts of the body
with musculoskeletal pain. Non-reactive ear points corresponded to parts
of the body with no reported pain. The statistically significant, overall
correct detection rate was 75.2%. When the pain was located on only
1 side of the body, electrical conductivity was significantly greater
at the sornatotopic ear point on the ipsilateral ear than at the corresponding
area of the contralateral ear. These results support the concept that
specific areas of the ear are related to specific areas of the body.
Double-blind assessment of auricular points
that are related to heart disorders was conducted by Saku et al in Japan.21
Reactive electropenneable points on the ear were defined as auricular
skin areas that had conductance of electrical current greater than 50
uA, indicating relatively low skin resistance. There was a significantly
higher frequency of reactive ear points at the Chinese heart points
in the inferior concha (84%), and on the tragus (59%), for patients
with myocardial infarction and angina pain than for a control group
of healthy subjects (I I %). There was no difference between the coronary
heart disease group and the control group in the electrical reactivity
of auricular points that did not represent the heart. The frequency
of electropermeable auricular points for the kidney (5%), stomach (6%),
liver (10%), elbow (I I %), or eye (3%) was the same for coronary patients
as for individuals without coronary problems. Whereas our findings"
supported the concept that Nogier's mesodermal zone on the antihelix
of the ear corresponds to the musculoskeletal system, Saku et al21 established
that specific points on the endodennal concha region of the ear are
associated with a visceral condition such as heart disease.
Quantified examinations of the electrical properties of
the skin have provided the most objective demonstration of the scientific
validity of acupuncture points.22-25
Observations that acupuncture points exhibited higher levels of skin
conductance or lower levels of skin resistance than surrounding skin
surface areas were first reported in the 1950s. In the 1970s, Matsumoto
showed that 80% of acupuncture points could be detected as low resistance
points.26 The electrical resistance
of acupuncture points was found to range from 100 to 900 kQ, (Please
note: Wherever you see kQ, please read k and Omega symbol) whereas
the electrical resistance of nonacupuncture points ranged from 1,100
to 11,700 kQ. Reichmanis et al27
further showed that meridian acupuncture points exhibit even lower electrical
resistance when there is pathology in the organ they represent. For
instance, electrodermal resistance on the lung meridian is lower in
the presence of a respiratory disorder. The normal, bilateral symmetry
of the electrical resistance of acupuncture points is disturbed when
there is unilateral pathology in the body. Those acupuncture points
that are ipsilateral to the site of body discomfort exhibit a lower
electrical resistance than the corresponding meridian point on the contralateral
side of the body. We found that auricular points showed a similar ipsilateral
pattern.20
Subsequent research on the differential electrodermal
activity of acupoints has continued to verify these earlier studies.
Hu et al28 examined 68 healthy
adults for computerized plotting of low skin resistance points (LSRPs).
A silver electrode was continuously moved over a whole area of body
surface while a reference electrode was fastened to the hand. Starting
from the distal ends of the 4 limbs, investigators moved the electrode
along the known meridians. The resistance of low skin impedance points
(LSIPs) was approximately 50 kQ, whereas the impedance at non-LSIPs
was typically 500 kQ. The LSIPs were distributed predominantly along
the 14 classic acupuncture meridian channels. A total of 64% of LSIPs
were located exactly on a channel; 83.3% were located within 3 mm of
a channel. Individual LSIPs could be found in non-channel areas in only
a few cases. There was not an uninterrupted, continuous line of low
skin impedance, but a series of electroactive points distributed along
the meridian channel. There was no marked natural fluctuation of skin
impedance; the distribution of LSIPs was considerably stable and replicable
from one day to the next.
The topography of LSRP's in rats was examined
by Chiou et al.29 A movable
search electrode consisted of a polished acupuncture needle applied
with uniform pressure that did not pierce the skin, while the reference
electrode was a needle inserted into the tail. Specific LSRP loci were
found to be distributed symmetrically and bilaterally over the shaved
skin of the animal's ventral, dorsal, and lateral surfaces. The arrangement
of these points corresponded to the acupuncture meridians found in humans.
The LSRP's were hypothesized to represent zones of autonomic concentration;
the higher electrical conductivity due to higher neural and vascular
elements beneath the points. The LSRP's gradually disappeared within
30 minutes after the animal's death.
Skin and muscle tissue samples were obtained
by Chan et al30 from 4 anesthetized
dogs. Acupuncture points, defined by regions of low skin resistance,
were compared with control points that exhibited higher electrodermal
resistance. The points were marked for later histological examination.
Concentration of substance P was significantly higher at skin acupuncture
points (3.33 ng/g) than at control skin points (2.63 ng/g) that did
not exhibit low skin resistance. Concentration of substance P was also
significantly higher in skin tissue samples (3.33 ng/g) than in the
deeper, muscle tissue samples (1.81 ng/g). Substance P is known to be
a spinal neurotransmitter found in nociceptive, afferent C-fibers. It
plays a role in pain transmission, stimulates contractility of autonomic
smooth muscle, induces subcutaneous liberation of histamine, causes
peripheral vasodilation, and leads to hypersensitivity of sensory neurons.
This neurotransmitter seems to activate a somatoautonomic reflex that
could account for the clinical observations of specific acupuncture
points that are both electrically active and tender to palpation.
Experimentally-induced changes in auricular
reflex points in rats were examined by Kawakita et al.31
The submucosal tissue of the stomach of anesthetized rats was exposed.
Acetic acid or saline was then injected into the stomach tissue. Impedance
of the auricular skin was measured by constant voltage, square-wave
pulses. A silver metal ball, the search electrode, was moved over the
surface of the rat's ear; a needle was inserted into subcutaneous tissue
to serve as the reference electrode. Injection of acetic acid led to
the gradual development of LSRP's on central regions of the rats ears,
auricular areas that correspond to the gastrointestinal region of human
ears. In healthy rats and in experimental rats before the operation,
low impedance points were rarely detected on the auricular skin. After
experimentally-induced peritonitis, there was a significant increase
in low impedance points (0-100 kQ) and moderate impedance points (100-500
kQ), but a decrease in high impedance points (>500 kQ). These results
demonstrated a reduction in the electrodermal resistance response to
experimentally-induced irritation of the internal organ that corresponded
to that auricular point. Histological investigation could not prove
the existence of sweat glands in the rat auricular skin.
The authors
suggest that the low impedance points are in fact related to sympathetic
control of blood vessels. It would have been intriguing if the investigators
had conducted further evaluation of the auricular low resistance sites
for concentrations of substance P, as Chan et at30
had done for body acupoints. The study by Kawakita et al31
I provides objective support for the organo-cutaneous reflexes described
by Dale,17 wherein low resistance
auricular acupuncture points appear in response to pathology of the
corresponding internal organ.
Changes in Brain Activity Following
Auricular Acupuncture for Obesity
An intriguing potential of auricular acupuncture
has been its clinical application for weight control. Sun and Xu32
treated obese patients with otoacupoint stimulation, another
term for ear acupressure. All patients were also given body acupuncture
during the 3-month study. The acupuncture group consisted of 110 patients
determined to be at least 20% over ideal body weight. They were compared
with 51 obese patients in a control group given an oral medication (1500
mg of Capsulae Olei Oenothera Erythrosepalae) for weight control. An
electrical point finder was used to determine the following auricular
points: mouth, esophagus, stomach, abdomen, hunger, Shen Men, lung,
and endocrine. Pressure pellets made from vaccaria seeds were applied
to the appropriate points of both ears. The body acupuncture points
needled were ST 25, ST 36, ST40, SP6, and PC 6. The acupuncture group
exhibited an average reduction of 5 kg of body weight, which was significantly
greater than the average 2-kg reduction in the control group. The percentage
of body fat was reduced by 3% in the acupuncture group and by 1.54%
in the control group, while the triglyceride levels were diminished
66.7 mg/dL in the acupuncture group and 38.4 mg/dL in the control group.
Total cholesterol levels were reduced by 27.6 mg/dL in the acupuncture
group and 33.3 mg/dL in the controls.
Arandomized controlled trial conducted by Richards
and Marley33 found that weight
loss was significantly greater for women in an auricular acupuncture
group than in a control group. Women in the acupuncture group were given
surface electrical stimulation to the ear acupoints for stomach and
Shen Men, whereas controls were given transcutaneous electrical stimulation
to the first joint of the thumb. Auricular acupuncture was theorized
to suppress appetite by stimulating the auricular branch of the vagal
nerve and by raising serotonin levels, both of which increase smooth
muscle tone in the gastric wall. Rather than examine changes in weight
measurements, Choy and Eidenschenk34
examined the effect of tragus clips on gastric peristalsis in 13 volunteers.
The duration of single peristaltic waves was measured before and after
the application of ear clips to the tragus. The frequency of peristalsis
was reduced by one-third with clips on the ear, and was returned to
normal levels with clips off. The ear clips were thought to produce
inhibition of vagal nerve activity, leading to a delay of gastric emptying,
which would then lead to a sense of fullness and early satiety. These
obesity studies on human subjects have received potential validation
from neurophysiological research in animals.
The areas of the brain that have been typically
related to weight control include 2 regions of the hypothalamus. The
ventromedial hypothalamus (VMH) has been referred to as a satiety center;
when the VMH is lesioned, animals fail to restrict their food intake.
In contrast, the lateral hypothalamus (LH) is referred to as a feeding
center, since stimulation of the LH induces animals to start eating.
Asamoto and Takeshig35 studied
selective activation of the hypothalamic satiety center using auricular
acupuncture in rats. Electrical stimulation of inner regions of the
rat ear, which correspond to auricular representation of the gastrointestinal
tract, produced evoked potentials in the VMH satiety center but not
in the LH feeding center.
Stimulation of more peripheral regions of the
rabbit ear did not activate hypothalamic-evoked potentials, indicating
the selectivity of auricular acupoint stimulation. Only the somatotopic
auricular areas near the region representing the stomach caused these
specific brain responses. Acupuncture needles were subsequently placed
into the same auricular sites as those that led to evoked potentials
in the VMH. After 16 days, the body weights of rats in the auricular
acupuncture group were significantly lower than those of a control group.
The same auricular acupuncture sites that led to hypothalamic activity
associated with satiety led to behavioral changes in food intake. Moreover,
auricular acupuncture had no effect in a different set of rats that
had incurred bilateral lesions of VMH. These results provide a compelling
connection between auricular acupuncture and a part of the brain associated
with neurophysiological regulation of feeding behavior.
In support of this evoked-potential research,
Shiraishi et al36 recorded
single-unit neuronal discharge rates in the VMH and LH of rats. Neurons
were recorded in the hypothalamus following electrical stimulation of
low resistance regions of the inferior concha of the rat ear, areas
of the auricle innervated by the vagus nerve and corresponding to the
stomach. Auricular stimulation tended to facilitate neuronal discharges
in the VMH and inhibit neural responses in the LH. Of 162 neurons
recorded in the VMH, 44.4% exhibited increased neuronal discharge rates
in response to auricular stimulation, 3.7% exhibited decreased activity,
and 51.9% showed no change. Of 224 neurons recorded in the LH feeding
center of 21 rats, 22.8% were inhibited by auricular stimulation, 7.
1 % were excited, and 70. 1 % were unaffected. When the analysis was
limited to 12 rats classified as behaviorally responding to auricular
acupuncture stimulation, 49.5% of LH neurons were inhibited, 15.5% were
excited, and 35% were not affected by auricular stimulation. A different
set of rats was given lesions of the VMH which led to significant weight
gain. In these hypothalamic obese rats, 53.2% of I I I LH neurons were
inhibited by auricular stimulation, 1.8% showed increased activity,
and 45% were unchanged. These neurophysiological findings suggest that
auricular acupuncture can selectively alter hypothalamic brain activity,
and is more likely to produce sensations of VMH satiety than reduction
of LH appetite.
Reduction of Nociceptive Neural Responses
by Acupuncture Stimulation
A central focus of neurophysiological research
on acupuncture treatment has been the assessment of changes in neural
responses related to pain. As stated previously, deep brain stimulation
of the periaqueductal gray area leads to pain reduction in rats, cats,
monkeys, and humans,8 an analgesic
effect that can be reversed by the opiate antagonist naloxone. Such
stimulation-produced analgesia by brain electrodes directly elevates
cerebrospinal fluid and blood plasma levels of endorphin in animals37
and humans.14,38
A review of the neurophysiological literature by Kho and Robertson16
provides empirical support for the role of the thalamus in acupuncture
analgesia. Afferent acupuncture impulses are thought to activate nociceptive
inhibitory pathways and selectively alter specific neurotransmitters.
Pert et al37
showed that 7-Hz auricular electrical stimulation through needles inserted
into the concha of the rat ear produced an elevation of hot plate threshold
that was reversed by administering naloxone. The behavioral analgesia
to auricular electroacupuncture was accompanied by a 60% increase in
radioreceptor activity in cerebrospinal fluid levels of endorphins,
a level that was significantly greater than that found in a control
group. Concomittant with these cerebrospinal fluid changes, auricular
electroacupuncture produced depletion in P-endorphin radioreceptor activity
in the VMH and the medial thalamus, but not the periaqueductal gray
area.
Similar findings in patients with back pain
were made by Clement-Jones et al.39
Low-frequency electrical stimulation of the concha led to relief of
pain within 20 minutes of the onset of electroacupuncture, and an accompanying
elevation of radioassays for cerebrospinal fluid B-endorphin (Note:
B- is Beta) activity in all 10 subjects. Abbate et al40
examined endorphin levels in 6 patients undergoing thoracic surgery
with 50% nitrous oxide and 50-Hz auricular electroacupuncture, compared
with 6 control patients who underwent surgery with 70% nitrous oxide
but no acupuncture. The auricular acupuncture patients needed less nitrous
oxide than the controls; acupuncture led to a significant increase in
B-endorphin immunoreactivity.
Kalyuzhny41
applied 15-Hz electrostimulation to the auricular lobe of rabbits, an
area corresponding to the jaw and teeth in humans. Behavioral reflexes
and cortical somatosensory-evoked potentials were measured in response
to tooth pulp stimulation. Auricular electroacupuncture produced a significant
decrease in both behavioral reflexes and cortical evoked potentials
to tooth stimulation. For most animals, the suppression of behavioral
and neurophysiological effects were abolished by injection of naloxone,
suggesting endorphinergic mechanisms. However, in a few rabbits, auriculoacupuncture
stimulation did not induce this naloxone-reversible effect. Naloxone
injections themselves led to an analgesic effect. It was suggested that
this paradoxical effect could be explained by an inhibition of
an antiopioid substance in select individuals.
Electrical stimulation of auricular acupuncture
points on the earlobe of rabbits, the auricular area that corresponds
to the trigerninal nerve, was performed by Fedoseeva et al.42
Auricular electroacupuncture led to a reduction of the amplitude of
cortical somatosensory potentials evoked by tooth pulp stimulation.
Intravenous injection of naloxone diminished the analgesic effect of
auricular electroacuncture at 15-Hz stimulation frequencies, but not
at 100-Hz stimulation. Conversely, injection of saralasin, an antagonist
for angiotensin 11, blocked the analgesic effect of 100-Hz auricular
acupuncture but not 15-Hz stimulation. The amplitude of cortical potentials
evoked by electrical stimulation of the hind limb was not attenuated
by stimulation of the auricular area for the trigeminal nerve.
Simmons and Oregon43
examined naloxone reversibility of auricular acupuncture analgesia to
acute, induced pain in human subjects. All 40 volunteers were assessed
for tooth pain threshold by a dental pulp tester. Dental pain levels
were determined before and after auriculotherapy, and then again after
double-blind injection of naloxone or placebo. Subjects were assigned
to I of 4 groups: true auricular electrical stimulation followed by
an injection of naloxone, true auricular electrical stimulation followed
by an injection of saline, placebo stimulation of the auricle followed
by naloxone, or placebo stimulation of the auricle followed by saline.
Dental pain thresholds were significantly increased by auricular electrical
stimulation conducted at appropriate auricular points for dental pain.
Pain thresholds were not altered by sham stimulation at inappropriate
auricular points. Naloxone produced a slight reduction in dental pain
threshold in the subjects given true stimulation; those given saline
showed a further increase in pain threshold. The minimal changes in
dental pain threshold shown in the sham auriculotherapy group were not
significantly affected by either saline or naloxone.
Both Sjolund and Eriksson44
and Simmons and Oregon43 noticed
that pain threshold levels did not completely return to baseline after
naloxone administration, suggesting nonopioid as well as endorphinergic
brain mechanisms.
Auricular acupuncture has also been shown to
suppress autonomic electrodermal activity associated with the startle
reflex to arousing stimuli. Young and McCarthy45
conducted a controlled clinical trial of 38 healthy volunteers. Forearm
electrodermal recordings (EDRs) to different stimuli were obtained when
a needle was inserted into the auricular sympathetic point. In another
set of subjects, EDR levels were recorded when a needle was inserted
into a placebo auricular point not associated with autonomic regulation.
Evoked EDR activity was consistently higher when needles were placed
in the placebo auricular point than in the sympathetic point. There
was thus a selective difference between the electrodermal effects of
appropriate and inappropriate auricular acupuncture stimulation, suggesting
that auriculotherapy attenuated the autonomic startle reflex.
Mechanisms for Withdrawal From Opiate
Drugs by Auricular Acupuncture
The discovery by Wen and Cheung46
that auricular acupuncture facilitates withdrawal from narcotic drugs
has led to a plethora of studies demonstrating the clinical use of this
technique for substance abuse.47,48
Auricular electroacupuncture has been shown to raise levels of metenkephalin
in humans," and B-endorphin levels in mice withdrawn from morphine.50-52
Kroening and Oregon53
examined 14 patients with chronic pain who were switched from their
original analgesic medication to an equivalent dose of oral methadone,
typically 80 mg/d. An electrodermal point finder was used to determine
areas of low skin resistance for the lung and Shen Men points. Needles
were bilaterally inserted into these 2 ear points and electrical stimulation
was initiated between 2 pairs of needles. After 45 minutes of electroacupuncture,
these patients were given periodic injections of small doses of naloxone
(0.04 mg every 15 minutes). The daily dose of methadone was cut in half
each day, presuming there were no adverse withdrawal effects. All 14
patients were withdrawn from methadone within 2 to 7 days (mean, 4.5
days). Only a few Patients reported minimal adverse effects of mild
nausea and agitation. The authors proposed that occupation of opiate
receptor sites by narcotic drugs leads to the inhibition of the activity
of natural endorphins, whereas auricular acupuncture facilitates withdrawal
from these drugs by activating the release of previously suppressed
endorphins. By giving small, incremental doses of naloxone after auricular
acupuncture, it was theorized that opiate receptor sites can be allowed
to gradually return to their original state.
Other biochemical changes also accompany auricular
acupuncture. Debrecini54 examined
changes in plasma corticotropin and gonadotropin hormone levels after
20-Hz electrical stimulation through needles inserted into the adrenal
point on the tragus of the ears of 20 healthy females. While gonadotropin
hormone secretions increased after electroacupuncture, corticotropin
levels remained the same. Jaung-Geng et al55
evaluated lactic acid levels from pressure applied to ear vaccarie seeds
positioned over the liver, lung, San Jiao endocrine, and thalamus (subcortex)
points. Using a within-subjects design, pressure applied to ear points
produced significantly lower levels of lactic acid after a treadmill
test than when ear seeds were placed over the same auricular points
but not pressed. Actual stimulation of these auricular acupressure points
appeared to reduce the toxic elevations of lactic acid build-up more
than did the control condition, perhaps due to improved peripheral blood
circulation.
CONCLUSION
The electrophysiological
studies conducted to date provide intriguing support for each of the
theoretical issues addressed. The 2 controlled studies of auricular
diagnosis both support the proposition that specific areas of the auricle
are related to specific areas of the body. The neurophysiological evidence
for a connection between acupuncture stimulation and brain pathways
related to a pain inhibitory system has been better established for
body acupuncture than ear acupuncture. However, both body points and
ear points are associated with endorphin and enkephalin release. Research
in rats and rabbits has shown that stimulation of the central concha
of the ear, which corresponds to the stomach selectively, activates
hypothalamic neurons associated with weight control; stimulation of
the auricular lobe region representing the trigerninal nerve attenuates
cortical-evoked potentials to tooth shock. These electrophysiological
studies suggest that auricular acupoints correspond to some areas of
body pathology; stimulation of lowresistance auricular points can lead
to site-specific alteration of brain activity. The exact relationship
of somatotopic points on the auricle to specific regions of the human
brain remains to be determined.
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AUTHOR INFORMATION
Dr
Terry Oleson is a licensed Clinical Psychologist practicing in West
Hollywood, California. He is Chair of the Department of Psychology at
the Califomia Graduate Institute, and President of the non-profit Center
for Oriental Medical Research and Education (COMRE). Formerly, he was
the Director of Research at the UCLA Pain Control Unit. Dr Oleson is
the author of Auriculotherapy Manual.
Terry
Oleson, PhD
8033 Sunset Blvd., PMB 2657
Los Angeles, CA 90048
Phone: 323-656-2084 - Fax: 323-656-2085
E-mail: terry-oleson@lunaarts.com
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