# Electrical Characterization of Proposed Transpositional Acupoints on the

Authors: Hyun-Jung Han; Sang-Jun Park; Kwang-sup Soh; Hyoun-Seok Myoung; Kyoung-Joung Lee; Vyacheslav Ogay; Yong-Heum Lee
Journal: Evidence-Based Complementary and Alternative Medicine
 (2011)

---

## Abstract

Specific electrical characteristicsof acupointswere investigated on the urinary bladder
(BL) meridian in 14 rats. BL acupointsand non-acupoints on the back were selected and
their electrical voltages were measured by using aSPACsystem.The mean voltages of each
point or each line were statistically analyzed by using the ANOVA test.The BL meridian
showed voltages higher than those of the reference line (P
<
.
05). Bilateral 1st BL lines presented higher voltages than
bilateral 2nd BL lines (P
<
.
05). Most BL acupoints had voltageshigher than those for the
corresponding reference points (P
<
.
05). In particular, theright BL16 exhibited the biggest
difference from the reference point, followed by the left extra BL point-2, the right
BL27, the left BL17, and theleft BL45. Additionally, the distributions of
neurofilamentsfor several points were investigated by using immunohistochemistry. There
was a trend for the BL acupoints to have larger numbers of neurofilaments than the
reference points, and that trend seemed to be directly proportional to the difference in
voltage between the points.In conclusion, BL acupoints on the back in ratsexhibited
specific electric and histologic characteristics. Therefore, those acupointsmay be
utilized to investigate the efficacy of acupuncturewith laboratory animals.


---

## Body

## 1. Introduction

Animal studies are a prerequisite for evaluating the efficacy and the mechanism of
acupuncture. Therefore, much research on acupuncture has been done using laboratory animals.
However, acupoints in laboratory animals, especially rats and mice, have not yet been
clearly defined, and the same acupoint may be interpreted differently by different
researchers.Until recently, acupoints in laboratory studies have been selected based on a
transpositional method that located the veterinary acupoints by transposing human
acupuncture points onto an animal’s anatomy [1–4]. Because the anatomy of rats was
considered to be nearly identical to that of humans, the locations of the acupoints and the
travel routes of the meridians in rats should resemble those in humans [5]. The method has generally been accepted by researchers;
in particular, transpositional acupoints for rats and mice were reported by Koh [2, 3].However, the selection of acupoints by using transpositional method differs with the
researcher [4]. For example, there was some
discrepancy defining the location of the ST 36 point (stomach meridian 36); Kim suggested
its location as 5 mm lower and lateral to the anterior tubercle of the tibia [6, 7], and Lim
suggested it as 2 mm lateral to the anterior tubercle of the tibia [8]. There are some reasons for these differences. First,
the locations of the acupoints may be subjectively interpreted by a researcher because the
locations of most acupoints are examined by using a relative anatomical proportion, rather
than an absolute number. Second, some anatomical differences exist between animals and
humans and even between the species of an animal, so some established acupoints of humans
may not correspond directly to those of animals. Such a discrepancy leads to different
outcomes even when the same acupoints are used in the laboratory animals. Therefore, the
results of acupuncture studies using animals are still controversial, and a serious
limitation on analyzing the efficacies of specific acupoints exists.To solve the above problem and to assist in confirming acupoints, researchers have
investigated the characteristics of acupoints, such as the electrical characteristics [9] or excitable muscle/skin-nerve complexes with enriched
nerve endings [5]. In particular, the electrical
characteristics of acupoints have been widely investigated and are regarded as the most
reliable characteristics [10]. Acupoints are
generally known to possess increased conductance, and compared to nonacupoints, acupuncture
meridians have been proposed to act as conduits for electrical currents [10–22].However, some limitations exist due to the poor quality of some studies: small sample
sizes, poor procedural description, lack of rigorous statistical analyses, and limited
region for evaluation, such as the extremities [10,
23]. Therefore, further studies are needed to
investigate the acupoints and the meridiansat more various sites on the body more
exactly.In this study, we tried to determine several acupoints in a rat by using transpositional
acupoints and electric characteristics. Of the large number of acupoints. The acupoints of
urinary bladder (BL) meridian on the back, which have frequently been used clinically and
experimentally, were investigated in this study. The purpose of this study was to use
electrical characteristics to establish the BL acupoints in a rat.


## 2. Materials and Methods

### 2.1. Animal Preparation

Fourteen Sprague-Dawley rats were utilized in this study. The animals were 8 weeks old,
were all female, and weighed about 200 g (200.85
±
3.20 g). The animals were housed in a
temperature-controlled environment (23°C) with 60% relative humidity and a 12-h
light/dark cycle. They were anesthetized through i.p. injection of a mixture of ketamine
hydrochloride (50 mL/kg) and xylazine hydrochloride (5 mL/kg). The animals
were placed in a sternal recumbency, and hair on the back region was completely removed
with great care to avoid iatrogenic damage to the skin on the backs. The procedures used
in the animal experiment were in full compliance with current international laws and
policies (European Convention for the Protection of Vertebrate Animals Used for
Experimental and Other Scientific Purposes). The protocols used in this study were
approved by the Institute of Laboratory Animal Resources of Seoul National University
(SNU-08310-1).


### 2.2. Selection of the Investigated Points

The BL meridian on the back includes two bilateral lines. The first BL line is the inner
line, and the second line is the outer line. The selection of BL lines was based on the
veterinary acupoints of a dog suggested by Kim et al., for which the 2nd BL line is the
longitudinal line extending from the end of the atlas wing, and the 1st BL line is the
longitudinal line extending from the middle point between the 2nd BL line and the midline
of the back [24]. Each acupoint of the 1st and the
2nd BL lines was selected lateral to the caudal border of the spinous process of each
vertebra and ranged from the 1st thoracic vertebrae (T1) to the 6th lumbar vertebrae (L6).
The nomenclature used for the individual acupoints in this study follows the nomenclature
for the traditional acupoints corresponding to the locations (Table 1). Although 8 points on the path of the BL meridian, such as the
points related to the 8th and the 9th thoracic vertebrae on the first BL line and to the
1st, 8th, and 9th thoracic and the 3rd, 4th, and 5th lumbar vertebrae on the second BL
line were not previously established acupoints, they were included. The nomenclatures for
these points are represented by EBL—(extra BL acupoints) in this study and ranged
from EBL-1 to EBL-8 (Table 1). As a reference
point, a non-acupoint located laterally 4 mm from the right 2nd BL line and located
on the same level as the individual BL acupoint was investigated. A diagram of the
investigated points is shown in Figure 1.Table 1
Nomenclature of the BL acupoints in this study.
Left side
*Land-
Right side
#2nd BL
§1st BL
mark vertebra
§1st BL
#2nd BL
EBL-1
BL11
T1
BL11
EBL-1
BL41
BL12
T2
BL12
BL41
BL42
BL13
T3
BL13
BL42
BL43
BL14
T4
BL14
BL43
BL44
BL15
T5
BL15
BL44
BL45
BL16
T6
BL16
BL45
BL46
BL17
T7
BL17
BL46
†EBL-3
†EBL-2
T8
†EBL-2
†EBL-3
†EBL-5
†EBL-4
T9
†EBL-4
†EBL-5
BL47
BL18
T10
BL18
BL47
BL48
BL19
T11
BL19
BL48
BL49
BL20
T12
BL20
BL49
BL50
BL21
T13
BL21
BL50
BL51
BL22
L1
BL22
BL51
BL52
BL23
L2
BL23
BL52
†EBL-6
BL24
L3
BL24
†EBL-6
†EBL-7
BL25
L4
BL25
†EBL-7
†EBL-8
BL26
L5
BL26
†EBL-8
BL53
BL27
L6
BL27
BL53
*T: thoracic vertebra, L: lumbar vertebra, individual BL acupoint located on
the 1st BL or the 2nd BL line to the lower border of the spinous process of each
landmark vertebra.
§1st BL: 1st urinary bladder meridian (the longitudinal line
extending from the middle point between the 2nd BL line and the midline of the
back), #2nd BL: 2nd urinary bladder meridian (the longitudinal line
extending from the end of the atlas wing), †EBL: extra BL
acupoints, which are acupoints that have not been previously established.Figure 1
Points investigated to determine the electrical characteristics on the back in a rat.
The points include transpositional acupoints of the BL meridian on the back (red
circles) and nonacupoints even though those were located on the path of the BL
meridian on the back (blue squares). The electrical voltages were compared to values
for corresponding reference points (X). C1: atlas, T1: 1st thoracic vertebra, L1: 1st
lumbar vertebra, S: sacrum, Gray bar: vertebra from T1 to S (midline of the back), 1st
(1st BL line, the longitudinal line extending from the middle point between the 2nd BL
line and the midline of the back), 2nd (2nd BL line, the longitudinal line extending
from the end of the atlas wing), and R (the line of reference points, 4 mm to
the right of the 2nd BL line).


### 2.3. Discrimination of Acupoints by Using the SPAC System

The electrical voltage of each point was measured three times by using a (SPAC single
power alternating current) system. The performance of the system is divided into three
functions—generating the SPAC stimulus pattern, measuring and displaying the
current value, and transmitting data to a computer. The system was designed with a
Microchip PIC18f252 microprocessor. The waveform generation circuit generates the SPAC
stimulus pattern. Figure2 presents a block diagram
and a schematic the system.Figure 2
Block diagram of the SPAC system. The black dotted rectangular area indicates of the
electrode in the SPAC system. An electrode guide pole encloses the electrode which is
linked with a 150-g sinker.At first, the microprocessor outputs a pulse of 4 kHz at 5 V. The SPAC
system supplies current to the body. The supplied current is converted to a voltage. Next,
the voltage is transferred to a personal computer. Then, a raw data point, which is the
impedance value of the detected acupoint, is displayed on a LED level-meter and is
indicated by a sound. The data transferred to the PC are displayed on an LCD by using a
GUI program (LabVIEW).


### 2.4. Immunohistochemistry

To compare the distributions of neurofilaments between BL acupoints and reference points,
we excised tissue explants (~1 cm2), including skin and muscle
(3 mm × 3 mm width), from the measured points of rats and fixed them
overnight at 4°C in a fixative consisting of 0.5% paraformaldehyde (Sigma, USA)
and 15% (v/v) saturated picric acid (Sigma, USA) in a 0.1 M sodium phosphate
buffer (SPB, pH 7.0) [25]. Prior to sectioning, the
tissue samples were infiltrated in O.C.T. compound (Sakura Finetek, USA) and frozen in
isopentane at the temperature of liquid nitrogen. The frozen samples were sectioned in the
horizontal plane by using a cryptome (Microm Lab. HM 505E, Germany) at
100 μm. Tissue sections were rinsed in PBS for
15 min to remove the O.C.T. embedding material and were incubated in a 3%
sodium-deoxycholate solution (Fluka, Italy) for 4 h at room temperature under mild
agitation in a 24-well plate (Falcon, USA). The specimens were rinsed twice with distilled
water and then three times with PBS for 1 h each. The sections were incubated in
10% normal goat serum (NGS) (Chemicon Inc., USA) overnight at 4°C and then for 1
day at 4°C in rabbit anti-neurofilament 160 kD polyclonal antibody
(1 : 1000, Abcam, UK). After the sections had been washed with PBS, they
were incubated in Alexa Flour 488 goat anti-rabbit IgG (H+L) (1 : 500)
(Invitrogen, USA) for 1 day at 4°C. All antibodies were diluted in 10% NGS
containing 0.1% NaN3 (pH 7.4). After each incubation with antibodies, sections were
washed in three times with PBS.Tissue sections were stained with DNA-specific dye (DAPI), mounted in antifading medium,
and observed with a stereomicroscope (MVX-10, Olympus, Japan). Images of thick sections
were obtained by using a digital camera (DP-70, Olympus, Japan). Ten serial images from
each sample were adjusted, merged into a common image, and analyzed with computer software
(Image J, v. 1.37, USA).


### 2.5. Statistical Analysis

The voltage of each measure point was represented by an average (mean), standard
deviation (SD), and standard error. The ANOVA test was applied to compare the mean
voltages of the measure points or to compare each BL to a reference line. Then,
Tukey’s multiple comparison test was performed for multiple comparisons; a value ofP
<
.
05 was considered significant.


## 2.1. Animal Preparation

Fourteen Sprague-Dawley rats were utilized in this study. The animals were 8 weeks old,
were all female, and weighed about 200 g (200.85
±
3.20 g). The animals were housed in a
temperature-controlled environment (23°C) with 60% relative humidity and a 12-h
light/dark cycle. They were anesthetized through i.p. injection of a mixture of ketamine
hydrochloride (50 mL/kg) and xylazine hydrochloride (5 mL/kg). The animals
were placed in a sternal recumbency, and hair on the back region was completely removed
with great care to avoid iatrogenic damage to the skin on the backs. The procedures used
in the animal experiment were in full compliance with current international laws and
policies (European Convention for the Protection of Vertebrate Animals Used for
Experimental and Other Scientific Purposes). The protocols used in this study were
approved by the Institute of Laboratory Animal Resources of Seoul National University
(SNU-08310-1).


## 2.2. Selection of the Investigated Points

The BL meridian on the back includes two bilateral lines. The first BL line is the inner
line, and the second line is the outer line. The selection of BL lines was based on the
veterinary acupoints of a dog suggested by Kim et al., for which the 2nd BL line is the
longitudinal line extending from the end of the atlas wing, and the 1st BL line is the
longitudinal line extending from the middle point between the 2nd BL line and the midline
of the back [24]. Each acupoint of the 1st and the
2nd BL lines was selected lateral to the caudal border of the spinous process of each
vertebra and ranged from the 1st thoracic vertebrae (T1) to the 6th lumbar vertebrae (L6).
The nomenclature used for the individual acupoints in this study follows the nomenclature
for the traditional acupoints corresponding to the locations (Table 1). Although 8 points on the path of the BL meridian, such as the
points related to the 8th and the 9th thoracic vertebrae on the first BL line and to the
1st, 8th, and 9th thoracic and the 3rd, 4th, and 5th lumbar vertebrae on the second BL
line were not previously established acupoints, they were included. The nomenclatures for
these points are represented by EBL—(extra BL acupoints) in this study and ranged
from EBL-1 to EBL-8 (Table 1). As a reference
point, a non-acupoint located laterally 4 mm from the right 2nd BL line and located
on the same level as the individual BL acupoint was investigated. A diagram of the
investigated points is shown in Figure 1.Table 1
Nomenclature of the BL acupoints in this study.
Left side
*Land-
Right side
#2nd BL
§1st BL
mark vertebra
§1st BL
#2nd BL
EBL-1
BL11
T1
BL11
EBL-1
BL41
BL12
T2
BL12
BL41
BL42
BL13
T3
BL13
BL42
BL43
BL14
T4
BL14
BL43
BL44
BL15
T5
BL15
BL44
BL45
BL16
T6
BL16
BL45
BL46
BL17
T7
BL17
BL46
†EBL-3
†EBL-2
T8
†EBL-2
†EBL-3
†EBL-5
†EBL-4
T9
†EBL-4
†EBL-5
BL47
BL18
T10
BL18
BL47
BL48
BL19
T11
BL19
BL48
BL49
BL20
T12
BL20
BL49
BL50
BL21
T13
BL21
BL50
BL51
BL22
L1
BL22
BL51
BL52
BL23
L2
BL23
BL52
†EBL-6
BL24
L3
BL24
†EBL-6
†EBL-7
BL25
L4
BL25
†EBL-7
†EBL-8
BL26
L5
BL26
†EBL-8
BL53
BL27
L6
BL27
BL53
*T: thoracic vertebra, L: lumbar vertebra, individual BL acupoint located on
the 1st BL or the 2nd BL line to the lower border of the spinous process of each
landmark vertebra.
§1st BL: 1st urinary bladder meridian (the longitudinal line
extending from the middle point between the 2nd BL line and the midline of the
back), #2nd BL: 2nd urinary bladder meridian (the longitudinal line
extending from the end of the atlas wing), †EBL: extra BL
acupoints, which are acupoints that have not been previously established.Figure 1
Points investigated to determine the electrical characteristics on the back in a rat.
The points include transpositional acupoints of the BL meridian on the back (red
circles) and nonacupoints even though those were located on the path of the BL
meridian on the back (blue squares). The electrical voltages were compared to values
for corresponding reference points (X). C1: atlas, T1: 1st thoracic vertebra, L1: 1st
lumbar vertebra, S: sacrum, Gray bar: vertebra from T1 to S (midline of the back), 1st
(1st BL line, the longitudinal line extending from the middle point between the 2nd BL
line and the midline of the back), 2nd (2nd BL line, the longitudinal line extending
from the end of the atlas wing), and R (the line of reference points, 4 mm to
the right of the 2nd BL line).


## 2.3. Discrimination of Acupoints by Using the SPAC System

The electrical voltage of each point was measured three times by using a (SPAC single
power alternating current) system. The performance of the system is divided into three
functions—generating the SPAC stimulus pattern, measuring and displaying the
current value, and transmitting data to a computer. The system was designed with a
Microchip PIC18f252 microprocessor. The waveform generation circuit generates the SPAC
stimulus pattern. Figure2 presents a block diagram
and a schematic the system.Figure 2
Block diagram of the SPAC system. The black dotted rectangular area indicates of the
electrode in the SPAC system. An electrode guide pole encloses the electrode which is
linked with a 150-g sinker.At first, the microprocessor outputs a pulse of 4 kHz at 5 V. The SPAC
system supplies current to the body. The supplied current is converted to a voltage. Next,
the voltage is transferred to a personal computer. Then, a raw data point, which is the
impedance value of the detected acupoint, is displayed on a LED level-meter and is
indicated by a sound. The data transferred to the PC are displayed on an LCD by using a
GUI program (LabVIEW).


## 2.4. Immunohistochemistry

To compare the distributions of neurofilaments between BL acupoints and reference points,
we excised tissue explants (~1 cm2), including skin and muscle
(3 mm × 3 mm width), from the measured points of rats and fixed them
overnight at 4°C in a fixative consisting of 0.5% paraformaldehyde (Sigma, USA)
and 15% (v/v) saturated picric acid (Sigma, USA) in a 0.1 M sodium phosphate
buffer (SPB, pH 7.0) [25]. Prior to sectioning, the
tissue samples were infiltrated in O.C.T. compound (Sakura Finetek, USA) and frozen in
isopentane at the temperature of liquid nitrogen. The frozen samples were sectioned in the
horizontal plane by using a cryptome (Microm Lab. HM 505E, Germany) at
100 μm. Tissue sections were rinsed in PBS for
15 min to remove the O.C.T. embedding material and were incubated in a 3%
sodium-deoxycholate solution (Fluka, Italy) for 4 h at room temperature under mild
agitation in a 24-well plate (Falcon, USA). The specimens were rinsed twice with distilled
water and then three times with PBS for 1 h each. The sections were incubated in
10% normal goat serum (NGS) (Chemicon Inc., USA) overnight at 4°C and then for 1
day at 4°C in rabbit anti-neurofilament 160 kD polyclonal antibody
(1 : 1000, Abcam, UK). After the sections had been washed with PBS, they
were incubated in Alexa Flour 488 goat anti-rabbit IgG (H+L) (1 : 500)
(Invitrogen, USA) for 1 day at 4°C. All antibodies were diluted in 10% NGS
containing 0.1% NaN3 (pH 7.4). After each incubation with antibodies, sections were
washed in three times with PBS.Tissue sections were stained with DNA-specific dye (DAPI), mounted in antifading medium,
and observed with a stereomicroscope (MVX-10, Olympus, Japan). Images of thick sections
were obtained by using a digital camera (DP-70, Olympus, Japan). Ten serial images from
each sample were adjusted, merged into a common image, and analyzed with computer software
(Image J, v. 1.37, USA).


## 2.5. Statistical Analysis

The voltage of each measure point was represented by an average (mean), standard
deviation (SD), and standard error. The ANOVA test was applied to compare the mean
voltages of the measure points or to compare each BL to a reference line. Then,
Tukey’s multiple comparison test was performed for multiple comparisons; a value ofP
<
.
05 was considered significant.


## 3. Results

### 3.1. Mean Voltages of the Acupoints on the BL Meridian and Reference Points

The mean voltages of the acupoints on the bilateral 1st and 2nd BL lines were
significantly higher than those of the reference points (Figure3). The mean (±SD) voltages were 2.579 (±0.482) for the left
1st BL line, 2.558 (±0.514) for the right 1st BL, 2.435 (±0.515) for the left
2nd BL, and 2.401 (±0.514) for the right 2nd BL meridian. The mean voltage of the
reference points was 2.015 (±0.389). The mean voltage of all BL meridians was
significantly higher than the mean voltage of all reference points
(P
<
.
05). In particular, the bilateral 1st BL lines exhibited a
significantly higher voltage than the bilateral 2nd BL lines (P
<
.
05).Figure 3
Mean voltage for each BL meridian on the back in a rat model. All four lines
belonging to the BL meridian represent significantly higher mean voltages than the
mean values for the reference points (nonacupoints on the back). In particular,
bilateral 1st BL lines show significantly higher voltages than bilateral 2nd BL lines
*P
=
.
000).In the comparison of the mean voltages between the individual pointson the same
transverse line extending from the vertebrae, most BL acupoints had significantly higher
voltages than the corresponding reference points (P
<
.
05). All acupoints on the bilateral1st BL lines had
significantly higher mean voltages than the corresponding reference points. On the other
hand, the mean voltages of several points on the bilateral 2nd lines were not
significantly different from those for the corresponding reference points: right EBL-1,
BL47, BL48, BL 50 and left BL48, BL49, BL 50, BL 52 (Figure 4).Figure 4
Most of the points on the BL meridian (red circles and blue squares) had
significantly higher mean voltages than the corresponding reference points (black X;P
<
.
05). The difference inmean voltages between the BL
acupoint and the corresponding reference point, Rt BL16, was the biggest difference
(yellow triangle), followed by Lt EBL-2, Rt BL27, Lt BL17, and Lt BL45 (yellow
circles). However, the mean voltages for several points on the 2nd BL line, including
Rt EBL-1, BL 47, BL 48, BL 50 and Lt BL 48, BL 49, BL 50, BL 52 (white X), were not
significantly different from the values for the corresponding reference points.The mean voltages of the BL acupoints ranged from 2.1124 to 2.761 (Figure5). The highest mean voltage was for Rt BL16 (2.761),
followed by Lt BL13 (2.7336), Lt BL14 (2.7005), Rt BL14 (2.6933), and Lt BL17 (2.6807).
The lowest mean voltage was 2.1124 for Lt BL52. The mean voltages of the corresponding
reference points ranged from 1.879 (transverse line extending from T8) to 2.1969
(transverse line extending from T4). As for the differences in mean voltages between the
BL acupoints and the corresponding reference points, Rt BL16exhibited the biggest
difference (0.8386), followed by Lt EBL-2 (0.7836), Rt BL27 (0.7357), Lt BL17 (0.7286),
and Lt BL45 (0.7286), while Lt BL52 showed the smallest difference (0.1321) (Figures 4 and 5).Figure 5
Mean voltage for each BL acupoint on the back in a rat model. The values for the BL
acupoints ranged from 2.1124 (Lt BL52) to 2.761 (Rt BL16) while the values for the
corresponding reference points ranged from 1.879 (level with T8) to 2.1969 (level with
T4). The biggest difference in the mean voltages between a BL acupoint and a
corresponding reference point was 0.8386 for Rt BL16 (level with T6) while the lowest
value was 0.1321 for Lt BL 52 (level with L2).


### 3.2. Distribution of Neurofilaments in BL Acupoints and Reference Points

To compare the distributions of neurofilaments between BL acupoints and reference points,
we selected several BL acupoints for immunohistochemistry. The acupoints were compared
with the corresponding reference points to eliminateregional differencesin the
distributions of neurofilaments. As a result, a distinct trend, most BL acupoints had
larger numbers of neurofilaments than the corresponding reference points (Figure6), was noted. The difference in the distributions of
neurofilaments between BL acupoints and reference points was related to the difference in
mean voltages between the points. BL acupoints and reference points exhibiting little
difference in the mean voltages seemed to exhibit little difference in the distributions
of neurofilaments (Figures 6(a) and 6(d)). On the other hand, points having a big
difference in the mean voltages seemed to also have a big difference in the distributions
of neurofilaments (Figures 6(b) and 6(e), and 6(c),
and 6(f)).Figure 6
Distribution of neurofilaments between BL acupoints (a, b, c) and the corresponding
reference points (d, e, f): (a) and (d) left BL 19 and its corresponding reference
point, (b) and (e) right BL23 and its corresponding reference point, and (c) and (f)
right BL25 and its corresponding reference point. (g) Comparison of the mean voltages
between the BL acupoints (a, b, c) and the reference points (d, e, f). (a) and (d)
show the least differences in mean voltages.


## 3.1. Mean Voltages of the Acupoints on the BL Meridian and Reference Points

The mean voltages of the acupoints on the bilateral 1st and 2nd BL lines were
significantly higher than those of the reference points (Figure3). The mean (±SD) voltages were 2.579 (±0.482) for the left
1st BL line, 2.558 (±0.514) for the right 1st BL, 2.435 (±0.515) for the left
2nd BL, and 2.401 (±0.514) for the right 2nd BL meridian. The mean voltage of the
reference points was 2.015 (±0.389). The mean voltage of all BL meridians was
significantly higher than the mean voltage of all reference points
(P
<
.
05). In particular, the bilateral 1st BL lines exhibited a
significantly higher voltage than the bilateral 2nd BL lines (P
<
.
05).Figure 3
Mean voltage for each BL meridian on the back in a rat model. All four lines
belonging to the BL meridian represent significantly higher mean voltages than the
mean values for the reference points (nonacupoints on the back). In particular,
bilateral 1st BL lines show significantly higher voltages than bilateral 2nd BL lines
*P
=
.
000).In the comparison of the mean voltages between the individual pointson the same
transverse line extending from the vertebrae, most BL acupoints had significantly higher
voltages than the corresponding reference points (P
<
.
05). All acupoints on the bilateral1st BL lines had
significantly higher mean voltages than the corresponding reference points. On the other
hand, the mean voltages of several points on the bilateral 2nd lines were not
significantly different from those for the corresponding reference points: right EBL-1,
BL47, BL48, BL 50 and left BL48, BL49, BL 50, BL 52 (Figure 4).Figure 4
Most of the points on the BL meridian (red circles and blue squares) had
significantly higher mean voltages than the corresponding reference points (black X;P
<
.
05). The difference inmean voltages between the BL
acupoint and the corresponding reference point, Rt BL16, was the biggest difference
(yellow triangle), followed by Lt EBL-2, Rt BL27, Lt BL17, and Lt BL45 (yellow
circles). However, the mean voltages for several points on the 2nd BL line, including
Rt EBL-1, BL 47, BL 48, BL 50 and Lt BL 48, BL 49, BL 50, BL 52 (white X), were not
significantly different from the values for the corresponding reference points.The mean voltages of the BL acupoints ranged from 2.1124 to 2.761 (Figure5). The highest mean voltage was for Rt BL16 (2.761),
followed by Lt BL13 (2.7336), Lt BL14 (2.7005), Rt BL14 (2.6933), and Lt BL17 (2.6807).
The lowest mean voltage was 2.1124 for Lt BL52. The mean voltages of the corresponding
reference points ranged from 1.879 (transverse line extending from T8) to 2.1969
(transverse line extending from T4). As for the differences in mean voltages between the
BL acupoints and the corresponding reference points, Rt BL16exhibited the biggest
difference (0.8386), followed by Lt EBL-2 (0.7836), Rt BL27 (0.7357), Lt BL17 (0.7286),
and Lt BL45 (0.7286), while Lt BL52 showed the smallest difference (0.1321) (Figures 4 and 5).Figure 5
Mean voltage for each BL acupoint on the back in a rat model. The values for the BL
acupoints ranged from 2.1124 (Lt BL52) to 2.761 (Rt BL16) while the values for the
corresponding reference points ranged from 1.879 (level with T8) to 2.1969 (level with
T4). The biggest difference in the mean voltages between a BL acupoint and a
corresponding reference point was 0.8386 for Rt BL16 (level with T6) while the lowest
value was 0.1321 for Lt BL 52 (level with L2).


## 3.2. Distribution of Neurofilaments in BL Acupoints and Reference Points

To compare the distributions of neurofilaments between BL acupoints and reference points,
we selected several BL acupoints for immunohistochemistry. The acupoints were compared
with the corresponding reference points to eliminateregional differencesin the
distributions of neurofilaments. As a result, a distinct trend, most BL acupoints had
larger numbers of neurofilaments than the corresponding reference points (Figure6), was noted. The difference in the distributions of
neurofilaments between BL acupoints and reference points was related to the difference in
mean voltages between the points. BL acupoints and reference points exhibiting little
difference in the mean voltages seemed to exhibit little difference in the distributions
of neurofilaments (Figures 6(a) and 6(d)). On the other hand, points having a big
difference in the mean voltages seemed to also have a big difference in the distributions
of neurofilaments (Figures 6(b) and 6(e), and 6(c),
and 6(f)).Figure 6
Distribution of neurofilaments between BL acupoints (a, b, c) and the corresponding
reference points (d, e, f): (a) and (d) left BL 19 and its corresponding reference
point, (b) and (e) right BL23 and its corresponding reference point, and (c) and (f)
right BL25 and its corresponding reference point. (g) Comparison of the mean voltages
between the BL acupoints (a, b, c) and the reference points (d, e, f). (a) and (d)
show the least differences in mean voltages.


## 4. Discussion

To investigate the electrical characteristics of transpositinal acupoints, we selected the
BL meridian, especially on the back, for two reasons: its significant usefulness in clinical
and experimental study and its ease of access. The BL meridian has significant meanings for
experiments on and to clinics of Oriental medicine. In particular, a well-known concept in
Oriental medicine is that most acupoints of the BL meridian on the back are organ-associated
points; that a certain acupoint in a region reflects the condition of a certain organ, for
example, BL13 is a lung-associated point and BL23 is a kidney-associated point, and so forth
[24, 26].
The points have been named Back-shu points and can be used in Oriental
medicineto diagnose and treat simultaneously disorders of the related organ.The acupoints of the BL meridian on the back are easy to access due to obvious anatomical
landmarks such as vertebra. However, according to previous studies, the selections of the
1st and the 2nd BL lines by using the transpositional method are a little different. In
human medicine, the 1st and the 2nd BL lines are 1.5 and 3cun lateral to
the midline of the back. However, the proportional method (using a concept of
cun) for human acupoint location is too complex for small laboratory
animals, offering great discrepancy between rats. In veterinary and laboratory studies, the
1st BL line is the longitudinal line of the thoracic costal tubercula [26] or of one-twentieth of the circumference of the thorax [4]. In canine acupuncture, as suggested by Kim et al. in
2004, the location of the 2nd BL line is the longitudinal line extending from the end of the
atlas wing, and the 1st BL line is the longitudinal line extending from the middle point
between the 2nd BL line and the midline of the back [24]. This method was the simplest and most accurate one to search for the BL
lines, and its use resulted in little discrepancy because the atlas wing is a more easily
accessible landmark. Therefore, to select the BL acupoints, we used transpositional
acupoints based on Kim’s method for canine acupuncture of [24].Existing acupoint discrimination instruments use a DC or a high-voltage impulse as an
acupoint stimulus source to find a low-impedance point (LIP). These stimulus sources cause
cell polarization and electrical shock. Also, when the skin is dry or the skin impedance is
high, it is difficult to discriminate acupoints and nonacupoints. At this time, many
problems exist because these instruments use high voltage/current and strongly press an
electrode probe to discriminate LIPs, which are the reasons for the low reproducibility and
discrimination rate of these instruments. To overcome these problems, a new LIP location
discrimination system was developed in 1998 by a Korean [27, 28]. This system, the SPAC, uses
optimal parameters for the meridian acupoint stimulus. This system uses a 2-electrode method
in which a common electrode is fixed at a part of body, after which a measuring probe is
contacted on a LIP or a non-LIP. The SPAC system uses 1.28-V (less than the hydrogen
ionization voltage [1.36 V]), 4-kHz bidirectional alternating signal with a
rectangular waveform (zero crossing start at 6 ms), and
1~20 μA (restricted maximum current, which depends on
the impedance of the human body between the two electrodes). Therefore, this method is able
to minimize the influence of the body, improve reproducibility, and reduce the pressure of
the electrode [27, 29]. Also, because the instrument has a new algorithm to automatically detect of
the condition of the skin (wet or dry), it is able to discriminate LIPs by using a low
electrode pressure and a low current source. The instrument uses various methods to display
the current measured at the LIP: a microampere meter, a level meter, speaker, sound, and a
computer monitor.Several external factors, such as the stratum corneum of the skin, skin moisture, and the
characteristics of the electrode, such as electrode polarization and electrode pressure,
affect the electrodermal measurements [10, 22, 23]. In
particular, the stratum corneum can act as the greatest contributor to the resistance to
electrical currents, and skin moisture can affect the electrical conductivity. Therefore,
skin integrity and hydration should be maintained during measurements; scratching of the
skin should be avoided, and consistent, uniform conditions should be maintained across tests
[22]. To decrease the errors due to the differences
in skin conditions, in this study, we kept relevant factors constant during the entire
procedure. The temperature (23°C) and the humidity (60%) were kept steady during
the experiment to maintain skin hydration, and depilation, instead of shaving, was used to
remove hair completely from the back because depilation does not damage the skin as much as
shaving. Also, to prevent errors due to the differences in the characteristics of the
electrode, we performed the measurements under the same conditions for all rats: the same
system, one inspector, and no difference in electrode pressure. In particular, we used an
electrode guide pole and the weight of a 150-g sinker to reduce the difference in electrode
pressure because manual operation might not put a fixed pressure on a electrode, so the
results might have lacked reproducibility. An electrode was placed in the electrode guide
pole and was linked to the weight. Therefore, the electrode was pressed regularly by the
weight and put pressure on the skin vertically.The BL acupoints on the back showed significantly higher voltages than the reference
points. In this SPAC system, a higher voltage indicates a lower electrical resistance and a
higher electric current. Furthermore, the acupoints on the 1st BL line showed significantly
higher voltage than those on the 2nd BL line. These results coincide with the established
idea of Oriental medicine that an important meridian exists on the back, the so-called BL
meridian, which has potent acupoints, organ-associated points, managing the functions of
internal organs. Of the two BL meridian, the 1st line of the BL meridian is generally known
to be the most effective meridian while the 2nd line of the BL meridian acts additionally to
assist the function of the 1st BL meridian.To identify a specific acupoint showing electrical characteristics, we investigated the
difference in the mean voltages between a specific acupoint and the corresponding reference
point. Rt BL 16, which showed the biggest difference, is calledDu-Shu, and
it is the governing vessel (GV) meridian association point that is mainly used to control
heart disease [24, 26]. Other points with big differences were related to specific organs or had
specific functions; Rt BL 27 is associated with the small intestine, and Lt BL 17 is
associated with the hematologic function [24, 26]. Therefore, those acupoints are of utility first for
investigating the effect of acupuncture related to specific organs or functions. Lt EBL-2
also showed a big difference even though it is not an established acupoint. We think it
could be a unique acupoint in rats. Therefore, further studies are needed to investigate the
specific role of this point.Another well-known characteristic of acupoints is the high density of nerve endings at the
acupoints [5, 30–33]. Due to enriched nerve
endings, needle stimulation of the nerves in a single acupoint could lead to activation of
multireceptors within an acupoint; further, it could propagate and enhance the activation of
other acupoints along the same meridian [5, 34, 35]. This
result was investigated along the BL and the spleen meridians for which a high density of
nerve endings is in perfect accord with the routes of those meridians at the lateral and the
medial edges of the paw of a rat, and the outcome was demonstrated at muscles of the
proximal portion of the anterior tibialis and of the proximal and the middle-distal portion
of the rectus femoris muscle [5]. In this study,
several acupoints along the BL meridian on the back were histologically investigated to
confirm the nerve densities on the acupoints, and the outcomes were similar to those of the
previous studies in that the nerve densities on the acupoints seemed to be higher than those
on the reference points. Interestingly, the nerve density at an acupoint seemed to be
related to the intensity of the electrical characteristic at that acupoint, with an acupoint
exhibiting a higher voltage also exhibiting a higher nerve density.Based on our results, transpositional BL acupoints on the back in rats present specific
properties as acupoints and meridians, including electrical and histological
characteristics. Therefore, those acupoints can be approved more objectively and can
beutilized in laboratory animals to confirm the efficacy of acupuncture on the BL meridian.
Furthermore, these results support the need for further study to discover the functions of
organ-associated points on the BL meridian, as noted in the concept of Oriental medicine,
provided the relation between the specific BL acupoint exhibiting electrical and
histological characteristics and the specific organ can be identified.



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*Source: 295475-2011-02-17.xml*