265
Pain,
4 (1978)
265-271
0 Elsevier/North-Holland
Biomedical
HAS ACUPUNCTURE
C&AR
GALEANO
and
Press
AN ANALGESIC
CHO
YUK
EFFECT
LEUNG
Department of Physiology and Pharmacology and Department of Sherbrooke, Centre Hospitalier Universitaire, Sherbrooke, (Accepted
June
17th,
IN THE RABBIT?
of Anoesthesia, Que. (Canada)
University
1977)
SUMMARY
We studied the effect of acupuncture stimulation on pain tolerance in rabbits. Painful stimulation was provided by a tungsten lamp focused on the snout. Four acupuncture points were selected: preocular, retroauricular, in the forepaw between the median and ulnar nerves and in the ears. A control series without acupuncture stimulation was also studied. Electrical stimulation was applied bilaterally through the acupuncture needles. A statistical analysis of the reaction time to the noxious stimulus demonstrated that the responses of the acupunctured animals were not significantly different from those of the controls. On the basis of operational behavioral measurements we conclude that the acupuncture procedure - as we did it - did not produce significant changes of pain tolerance in rabbits.
INTRODUCTION
The analgesic effect of acupuncture has been studied in humans and animals during the last 2 decades. A biochemical factor was first suggested in China on the basis of analgesia obtained by: (1) The transfer of plasma or cerebrospinal fluid from a “donor” (acupunctured) to a “receptor” (nonacupunctured) rabbit, and (2) cross-circulation experiments in which only one animal was acupunctured but both showed analgesia [4,5]. The recent discovery of endorphins and also the block of the analgesic effect of acupuncture by naloxone and hypophysectomy give to this type of analgesia a possible biochemical basis, in addition to the neurophysiological theories of neural interaction [ 7,8,10]. This article deals with our study of the analgesic effect of acupuncture in rabbits, in an attempt to duplicate the Chinese reports and to assess the reliability of rabbits for this type of research.
266 MATERIAL
AND METHODS
Thirty-four experiments were performed on 29 rabbits (New Zealand and Californian) of both sexes, weighing between 2.5 and 3.5 kg. Painful stimulation was provided by a 375 W tungsten lamp (GE photo EBR) or a 600 W torchlamp (SV, TL2) focused on the snout via a lens and an iris diaphragm. The distances between the lamp, the lens and the rabbit were kept constant in each experiment, and were regulated at the beginning of the session in order to obtain an avoidance response (turning of the head, withdrawal, general movements or vocalization) with a latency of 5-50 sec. The same stimulation applied to the skin of the authors of this report was painful. No macroscopic lesion was observed in the snout. The response was evaluated by the reaction time in seconds between the application of the heat stimulus and the response. This was considered the “pain tolerance” and was controlled by two observers. This method of measurement is generally considered reliable [2]. If no response was subsequently evident, we stopped the noxious stimulation at 150 set, to avoid excessive pain and damage of the skin. The rabbits were held in a soft tissuebag, with only the head protruding in a comfortable position, frontal to the noxious stimulator. The eyes were protected with an opaque film, and the animals were allowed to adapt to this restrained position before the stimulation was started (Fig. 1). Acupuncture needles were inserted manually (using an insect pin attached to a handle) or chronically implanted (silver rings) in the subcutaneous tissue at selected points. Being unaware of a Chinese atlas of acupuncture in rabbits, we selected the points by analogy with man [ 31. The following sites were used : (1) series A (9 animals): preocular (infraorbital), close to the exit point of the fifth nerve (Cheng-Chi, Chuan-Liao) manually implanted; the needle was introduced 1.5 cm toward the external side of the mouth; (2) series B (11 animals): retroauricular, close to the exit point of the seventh nerve (Hsia-i-feng, Hsia-Kuan) manually implanted; the needle was introduced 1.5-2 cm toward the masseter muscle; (3) series c
Fig. 1. Scheme of the equipment setup. Note the rabbit into a soft bag, in front noxious stimulator focused on the snout through a lens and an iris diaphragm.
of the
261
(5 animals): chronically implanted electrodes in the forepaw, between the median and ulnar nerves (several Chinese points are related to these nerves (Nei-Kuan, Wai-Kuan, Hsi-Men, T’ung-Li, Ho-Ku, etc.); (4) series D (4 animals): in the ears, ventral side (point zero of Nogier-Niboyet [ 91 manually implanted; the needle was introduced 1 cm toward the base of the ears. In all cases the electrodes were placed bilaterally. We also studied a control series (series CO, 5 animals) without electrodes. The electrical stimulation was provided by a Hewlett-Packard function generator (3310A) or a Grass S4 stimulator. We used square, triangle, sinewave and biphasic single-pulse stimulation in monopolar and bipolar connections. The voltage was adjusted in each animal to obtain small myoclonic movements, in general 3-10 V. The frequency was 5 and 10 c/set; in a few cases we increased the frequency to 10,000 c/set. Distinct manifestations of pain were not seen. We always monitored, with the oscilloscope, both the zero level and the voltage of the stimulus, in order to avoid any supplementary DC stimulation and electrolytic lesion. In all cases we used bilateral stimulation. The experiments were done as follows: (1) Control series (CO). Each animal was submitted to a first period of 5 noxious stimuli applied at 5-6 min intervals, followed by 20 min of rest. Then, there was a second period of stimulation with 15 noxious stimuli at 5-6 min intervals (Fig. 2). (2) Acupuncture series (series A-D). Each animal was subjected first to a period of noxious stimulation, as in the control series, followed immediately by the acupuncture stimulation. After 20 min of acupuncture, the second period of noxious stimulation was started as in the control series. We did not interrupt the acupuncture stimulation during the application of the noxious stimuli (Fig. 2). The first period served as a control for the evaluation of the pain sensibility and behavioral responses of each rabbit. The period of 20 min gave time, in the acupuncture series, for the supposedly analgesic effect to develop. In the second period the test for the analgesia was carried out. The treatment of data and statistics was done according to the Biomedical
CONTROL first l
SERIES
0
l
0
ACUPUNCTURE ..*a*
second
period 0
period
•~*ooo@*~~aa~ea
SERIES l
*eoeeoeeeeeeee
0
to
20 min.
Fig. 2. Scheme of the session. The black dots indicate the noxious stimulation on the snout. The thick black horizontal line indicates the acupuncture stimulation. Note the first and second periods of noxious stimulation separated by an interval of 20 min. The control series has no acupuncture stimulation.
Computer Program (BMDP) Package of U.C.L.A. with the same procedure being used during control and acupuncture series. We did not administer any drug during the experiments. General anesthesia with Nembutai (40 mgikg) was given for the implantation of chronic electrodes, and antibiotics were administered during 3 days. The experiments started 1 week later. RESULTS series The animals were awake and calm throughout the session. The responses were vigorous at the outset, then, in some cases, they became less distinct or appeared as small generalized myoclonic jerks followed by turning of the head which was considered the avoidance response. The reaction time to each stimulation was tabulated; then, the first 2 responses of the first period were discarded and the arithmetic mean of the reaction time of the remaining three was calculated. We gave to this mean the relative value of I, and it represented an estimate of the control response of each animal. We also discarded the first 2 responses of the second period and gave to the reaction time of each of the following ones, a relative value according to the ratio to the first period mean, A value of 1 indicates the same reaction time as the control mean; lower than 1 denotes a shorter reaction time, and higher than 1 a longer reaction time than the control mean. Table I shows the relative value 1 of the first period. In the second period, the first number of the first column (0.69) represents the mean of the third response of all animals in this series; next, in the second column is the standard deviation (0.47) of thisgroup of data. The same procedure was used for the following responses. The reaction time during the second period was, in general, shorter than control, with a general mean of 0.74, range from 0.49 to 1.12, and standard deviations between 0.12 and 0.74. We did not utilize the first 2 responses of the first and second periods of painful stimulation, in order to avoid changes due to surprise, learning or fear at the beginning of each period. (A) Control
(B) Acupuncture
series
The rabbits were calm and with myotic pupils through the sessions. They showed the same type of avoidance response as in the control series. Table I, series A-D, shows the mean and the standard deviations of data. The acupuncture at the preocular point (series A) increased the general mean to 1.22, with a range from 0.64 to 2.34 and stand~d deviations between 0.25 and 2.25. The retroauricutar point (series B) gave a general mean of 1.14 with a range from 0.88 to 1.40 and standard deviations between 0.25 and 0.82. The forepaw point (series C) gave the longest mean, 1.93, with a range from 1.32 to 2.56 and standard deviations between 0.52 and 2.37. The auricular point (series D) gave similar results to the control series: mean of
269
TABLE
I
MEANS
AND STANDARD
Control series Means -
Means
SD.
0.34 0.35 0.37 0.32 0.31 0.74 0.46 0.66 0.20 0.55 0.12 0.52
x = 0.74
SD.
1 .oo
Second period 0.69 0.47
1.10 0.90 0.64 0.89 0.99 1.85 1.28 1.63 1.22 1.32 2.34 0.94 0.79
Acupunct. series C
Acupunct. series B -
Acupunct. series A _
First period 1.00
0.77 0.63 0.79 0.74 0.73 1.12 0.66 0.88 0.49 0.71 0.61 0.83
DEVIATIONS
Means
S.D.
x = 1.22
1.29 1.25 0.96 1.11 1.12 1.26 1.21 1.11 1.40 1.18 0.95 0.88 1.04
Means S.D. ____ ____
0.67 0.60 0.26 0.43 0.52 0.80 0.75 0.47 0.82 0.82 0.25 0.34 0.33
Means
S.D.
1.00
1.00
1.00
0.74 0.38 0.25 0.36 0.59 2.25 0.89 2.21 0.75 0.77 1.43 0.37 0.31
Acupunct. series D
1.32 2.17 2.08 2.00 2.56 2.53 1.87 1.93 1.78 1.32 1.68
1.15 2.26 1.24 2.37 2.02 2.25 0.78 1.06 1.09 0.52 1.09
x = 1.14
0.92
1.06 0.78 0.89 0.83 0.61 0.81 0.62 0.73 0.68 0.74 0.68 0.70
0.33 0.12 0.41 0.39 0.29 0.32 0.27 0.14 0.29 0.26 0.23 0.43 0.28
x = 0.77
0.77 with a range from 0.61 to 1.06 and standard deviations between 0.12 and 0.43. Table II shows the analysis of the variance of each series (A-D) in relation to that of the control. The differences observed between each acupuncture TABLE
II
ANALYSIS
OF VARIANCE
F
P F exceeded
3.29 2.64
2.24
0.28
1 14
9.99 3.81
2.61
0.12
34.31 80.60
1 7
34.31 11.51
2.97
0.12
0.02 6.53
1 6
0.02 1.08
0.02
0.87
Sum of squares
df
3.29 31.78
1 12
9.99 53.43
Mean square
CO us. A Groups Error CO vs. B Groups Error co
vs. c
Groups Error CO vs. D Groups Error
270
series and the control were not significant. Results were obtained using the 11 first values of the second period of Table I. Results using all the data were also non-si~ificant. DISCUSSION
The most striking finding of this study was that acupuncture, in the 4 sites explored, did not produce analgesia in the rabbit. In some isolated cases, the reaction time increased markedly during a few stimulations, only to return to the control level again, despite continuation of the acupuncture stimulation. These rabbits were responsible for the transient increase of the mean and the high standard deviations observed, particularly evident in series A and C. Repetition of the same schedule of stimulation after 2-15 days in these animals, which demonstrated a transient increase of their reaction time, failed to confirm the lengthening of the reaction time. In several animals which showed transient increases in their pain tolerance, we repeated the sessions of acupuncture changing the shape of the wave, and the intensity, frequency or duration of the acupuncture stimulation; we did not obtain analgesic effects. These experiments with a changed protocol were not included in the Tables I and II. We did not consider the transient lengthening of the reaction time as representative of acupuncture analgesia, which is characterized by a steady level of high pain threshold and pain tolerance; it appears after several minutes of acupuncture stimulation and maintains a stable intensity sufficient to permit surgical procedures; it lasts longer than the period of acupuncture stimulation, and then gradually fades 141. The occasional increase of pain tolerance observed in our experiments could be due to several factors, such as sleep, fatigue, fear, attention, learning, even transitory periods of animal hypnosis [ 1,6,12]. Some animals breathed fast and lifted the nose very fast, keeping it wet during the heat stimuli. Our results did not confirm the existence of the intense analgesic effect of acupuncture reported by Niboyet [9]. He used diazepam as premeditation, in an unspecified dose, and the animal appeared very hypnotonic in several pictures of Niboyet’s book. We do not know, therefore, if the reported analgesia was due to the effect of acupuncture alone. He did report neither a control series nor quantitative data. Rabischong et al. [ 111 reported acupuncture analgesia in 72% of their rabbits. They used a prick of the hind leg skin as painful stimulation and electrical stimulation of acupuncture needles in the hip (Tche-Pienn) and the calf (Tsou-Sann-Li). They did not report quantitative data. They also reported specific analgesia in the calf and thigh, and the transfer of the serum from these animals (donors) to control rabbits, produced analgesia confined to the same area as that of the donor. These results need to be confirmed with careful consideration to natural variations of pain sensibility in different areas of the skin. We cannot make inferences about pain in absolute terms. Nevertheless, on the bases of operational behavioral measurements, the acupuncture proce-
271
dure - as we did it - did not produce tolerance in rabbits.
significant
long-lasting
changes of pain
ACKNOWLEDGEMENTS
We wish to thank Dr. G.F. Brindle (Department of Anaesthesia, University of Sherbrooke) for comments on this manuscript and Mr. R. Black (Service d’Informatique, University of Sherbrooke) for the statistics. This research was supported by Grant 3-05-1511-1-0001-110-402-9 of the Ministere des Affaires Sociales. Dr. G.F. Brindle is the director of the research project. REFERENCES
4 5
6 7 8 9 10
11 12
Carli, G., Farabollini, F. and Fontani, G., Responses to painful stimuli during animal hypnosis, Advanc. Pain Res. Ther., 1 (1976) 727-731. Chapman, CR., Measurement of pain: problems and issues, Advanc. Pain Res. Ther., 1 (1976) 345-353. Fogarty International Center, Acupuncture Anesthesia (a translation of a Chinese publication of the same title), DHEW Publication, NIH, Bethesda, Md., 1975, 339 pp. Kaada, B., Neurophysiology and acupuncture: a review, Advanc. Pain Res. Ther., 1 (1976) 733-741. Kaada, B., Hoel, E., Leseth, K., Nygaard-Ostby, B., Setekleiv, J. and Stovner, J., Acupuncture analgesia in the People’s Republic of China, T. norske Laegeforen., 94 (1974) 417-442. Keely, D.D. and Glusman, M., Emotional and psychological factors modifying the pain response of animals, Advanc. Pain Res. Ther., 1 (1976) 335-341. Marx, J.L., Analgesia: how the body inhibits pain perception, Science, 195 (1977) 471-473. Melzack, R. and Wall, P.D., Pain mechanisms: a new theory, Science, 150 (1965) 971-979. Niboyet, J.E.H., I’Anesthesie par l’Acupuncture, Maisonneuve, 1973, 433 pp. Pomeranz, B., Cheng, R. and Law, P., Acupuncture reduces electrophysiological and behavioral responses to ‘noxious stimuli: pituitary is implicated, Exp. Neural., 54 (1977) 172-178. Rabischong, P., Niboyet, J.E.H., Terral, C., Senelar, R. et Casez, R., Bases experimentales de l’analgesie acupuncturale, Nouv. Presse med., 4 (1975) 2021-2027. Segundo, J.P., Galeano, C., Sommer-Smith, J.A. and Roig, J.A., Behavioural and EEG effects of tones “reinforced” by cessation of painful stimuli. In: J.F. Delafresnaye (Ed.), Brain Mechanisms and Learning, Blackwell, Oxford, 1962, pp. 265-291.
Pain,
4 (1978)
265-271
0 Elsevier/North-Holland
Biomedical
HAS ACUPUNCTURE
C&AR
GALEANO
and
Press
AN ANALGESIC
CHO
YUK
EFFECT
LEUNG
Department of Physiology and Pharmacology and Department of Sherbrooke, Centre Hospitalier Universitaire, Sherbrooke, (Accepted
June
17th,
IN THE RABBIT?
of Anoesthesia, Que. (Canada)
University
1977)
SUMMARY
We studied the effect of acupuncture stimulation on pain tolerance in rabbits. Painful stimulation was provided by a tungsten lamp focused on the snout. Four acupuncture points were selected: preocular, retroauricular, in the forepaw between the median and ulnar nerves and in the ears. A control series without acupuncture stimulation was also studied. Electrical stimulation was applied bilaterally through the acupuncture needles. A statistical analysis of the reaction time to the noxious stimulus demonstrated that the responses of the acupunctured animals were not significantly different from those of the controls. On the basis of operational behavioral measurements we conclude that the acupuncture procedure - as we did it - did not produce significant changes of pain tolerance in rabbits.
INTRODUCTION
The analgesic effect of acupuncture has been studied in humans and animals during the last 2 decades. A biochemical factor was first suggested in China on the basis of analgesia obtained by: (1) The transfer of plasma or cerebrospinal fluid from a “donor” (acupunctured) to a “receptor” (nonacupunctured) rabbit, and (2) cross-circulation experiments in which only one animal was acupunctured but both showed analgesia [4,5]. The recent discovery of endorphins and also the block of the analgesic effect of acupuncture by naloxone and hypophysectomy give to this type of analgesia a possible biochemical basis, in addition to the neurophysiological theories of neural interaction [ 7,8,10]. This article deals with our study of the analgesic effect of acupuncture in rabbits, in an attempt to duplicate the Chinese reports and to assess the reliability of rabbits for this type of research.
266 MATERIAL
AND METHODS
Thirty-four experiments were performed on 29 rabbits (New Zealand and Californian) of both sexes, weighing between 2.5 and 3.5 kg. Painful stimulation was provided by a 375 W tungsten lamp (GE photo EBR) or a 600 W torchlamp (SV, TL2) focused on the snout via a lens and an iris diaphragm. The distances between the lamp, the lens and the rabbit were kept constant in each experiment, and were regulated at the beginning of the session in order to obtain an avoidance response (turning of the head, withdrawal, general movements or vocalization) with a latency of 5-50 sec. The same stimulation applied to the skin of the authors of this report was painful. No macroscopic lesion was observed in the snout. The response was evaluated by the reaction time in seconds between the application of the heat stimulus and the response. This was considered the “pain tolerance” and was controlled by two observers. This method of measurement is generally considered reliable [2]. If no response was subsequently evident, we stopped the noxious stimulation at 150 set, to avoid excessive pain and damage of the skin. The rabbits were held in a soft tissuebag, with only the head protruding in a comfortable position, frontal to the noxious stimulator. The eyes were protected with an opaque film, and the animals were allowed to adapt to this restrained position before the stimulation was started (Fig. 1). Acupuncture needles were inserted manually (using an insect pin attached to a handle) or chronically implanted (silver rings) in the subcutaneous tissue at selected points. Being unaware of a Chinese atlas of acupuncture in rabbits, we selected the points by analogy with man [ 31. The following sites were used : (1) series A (9 animals): preocular (infraorbital), close to the exit point of the fifth nerve (Cheng-Chi, Chuan-Liao) manually implanted; the needle was introduced 1.5 cm toward the external side of the mouth; (2) series B (11 animals): retroauricular, close to the exit point of the seventh nerve (Hsia-i-feng, Hsia-Kuan) manually implanted; the needle was introduced 1.5-2 cm toward the masseter muscle; (3) series c
Fig. 1. Scheme of the equipment setup. Note the rabbit into a soft bag, in front noxious stimulator focused on the snout through a lens and an iris diaphragm.
of the
261
(5 animals): chronically implanted electrodes in the forepaw, between the median and ulnar nerves (several Chinese points are related to these nerves (Nei-Kuan, Wai-Kuan, Hsi-Men, T’ung-Li, Ho-Ku, etc.); (4) series D (4 animals): in the ears, ventral side (point zero of Nogier-Niboyet [ 91 manually implanted; the needle was introduced 1 cm toward the base of the ears. In all cases the electrodes were placed bilaterally. We also studied a control series (series CO, 5 animals) without electrodes. The electrical stimulation was provided by a Hewlett-Packard function generator (3310A) or a Grass S4 stimulator. We used square, triangle, sinewave and biphasic single-pulse stimulation in monopolar and bipolar connections. The voltage was adjusted in each animal to obtain small myoclonic movements, in general 3-10 V. The frequency was 5 and 10 c/set; in a few cases we increased the frequency to 10,000 c/set. Distinct manifestations of pain were not seen. We always monitored, with the oscilloscope, both the zero level and the voltage of the stimulus, in order to avoid any supplementary DC stimulation and electrolytic lesion. In all cases we used bilateral stimulation. The experiments were done as follows: (1) Control series (CO). Each animal was submitted to a first period of 5 noxious stimuli applied at 5-6 min intervals, followed by 20 min of rest. Then, there was a second period of stimulation with 15 noxious stimuli at 5-6 min intervals (Fig. 2). (2) Acupuncture series (series A-D). Each animal was subjected first to a period of noxious stimulation, as in the control series, followed immediately by the acupuncture stimulation. After 20 min of acupuncture, the second period of noxious stimulation was started as in the control series. We did not interrupt the acupuncture stimulation during the application of the noxious stimuli (Fig. 2). The first period served as a control for the evaluation of the pain sensibility and behavioral responses of each rabbit. The period of 20 min gave time, in the acupuncture series, for the supposedly analgesic effect to develop. In the second period the test for the analgesia was carried out. The treatment of data and statistics was done according to the Biomedical
CONTROL first l
SERIES
0
l
0
ACUPUNCTURE ..*a*
second
period 0
period
•~*ooo@*~~aa~ea
SERIES l
*eoeeoeeeeeeee
0
to
20 min.
Fig. 2. Scheme of the session. The black dots indicate the noxious stimulation on the snout. The thick black horizontal line indicates the acupuncture stimulation. Note the first and second periods of noxious stimulation separated by an interval of 20 min. The control series has no acupuncture stimulation.
Computer Program (BMDP) Package of U.C.L.A. with the same procedure being used during control and acupuncture series. We did not administer any drug during the experiments. General anesthesia with Nembutai (40 mgikg) was given for the implantation of chronic electrodes, and antibiotics were administered during 3 days. The experiments started 1 week later. RESULTS series The animals were awake and calm throughout the session. The responses were vigorous at the outset, then, in some cases, they became less distinct or appeared as small generalized myoclonic jerks followed by turning of the head which was considered the avoidance response. The reaction time to each stimulation was tabulated; then, the first 2 responses of the first period were discarded and the arithmetic mean of the reaction time of the remaining three was calculated. We gave to this mean the relative value of I, and it represented an estimate of the control response of each animal. We also discarded the first 2 responses of the second period and gave to the reaction time of each of the following ones, a relative value according to the ratio to the first period mean, A value of 1 indicates the same reaction time as the control mean; lower than 1 denotes a shorter reaction time, and higher than 1 a longer reaction time than the control mean. Table I shows the relative value 1 of the first period. In the second period, the first number of the first column (0.69) represents the mean of the third response of all animals in this series; next, in the second column is the standard deviation (0.47) of thisgroup of data. The same procedure was used for the following responses. The reaction time during the second period was, in general, shorter than control, with a general mean of 0.74, range from 0.49 to 1.12, and standard deviations between 0.12 and 0.74. We did not utilize the first 2 responses of the first and second periods of painful stimulation, in order to avoid changes due to surprise, learning or fear at the beginning of each period. (A) Control
(B) Acupuncture
series
The rabbits were calm and with myotic pupils through the sessions. They showed the same type of avoidance response as in the control series. Table I, series A-D, shows the mean and the standard deviations of data. The acupuncture at the preocular point (series A) increased the general mean to 1.22, with a range from 0.64 to 2.34 and stand~d deviations between 0.25 and 2.25. The retroauricutar point (series B) gave a general mean of 1.14 with a range from 0.88 to 1.40 and standard deviations between 0.25 and 0.82. The forepaw point (series C) gave the longest mean, 1.93, with a range from 1.32 to 2.56 and standard deviations between 0.52 and 2.37. The auricular point (series D) gave similar results to the control series: mean of
269
TABLE
I
MEANS
AND STANDARD
Control series Means -
Means
SD.
0.34 0.35 0.37 0.32 0.31 0.74 0.46 0.66 0.20 0.55 0.12 0.52
x = 0.74
SD.
1 .oo
Second period 0.69 0.47
1.10 0.90 0.64 0.89 0.99 1.85 1.28 1.63 1.22 1.32 2.34 0.94 0.79
Acupunct. series C
Acupunct. series B -
Acupunct. series A _
First period 1.00
0.77 0.63 0.79 0.74 0.73 1.12 0.66 0.88 0.49 0.71 0.61 0.83
DEVIATIONS
Means
S.D.
x = 1.22
1.29 1.25 0.96 1.11 1.12 1.26 1.21 1.11 1.40 1.18 0.95 0.88 1.04
Means S.D. ____ ____
0.67 0.60 0.26 0.43 0.52 0.80 0.75 0.47 0.82 0.82 0.25 0.34 0.33
Means
S.D.
1.00
1.00
1.00
0.74 0.38 0.25 0.36 0.59 2.25 0.89 2.21 0.75 0.77 1.43 0.37 0.31
Acupunct. series D
1.32 2.17 2.08 2.00 2.56 2.53 1.87 1.93 1.78 1.32 1.68
1.15 2.26 1.24 2.37 2.02 2.25 0.78 1.06 1.09 0.52 1.09
x = 1.14
0.92
1.06 0.78 0.89 0.83 0.61 0.81 0.62 0.73 0.68 0.74 0.68 0.70
0.33 0.12 0.41 0.39 0.29 0.32 0.27 0.14 0.29 0.26 0.23 0.43 0.28
x = 0.77
0.77 with a range from 0.61 to 1.06 and standard deviations between 0.12 and 0.43. Table II shows the analysis of the variance of each series (A-D) in relation to that of the control. The differences observed between each acupuncture TABLE
II
ANALYSIS
OF VARIANCE
F
P F exceeded
3.29 2.64
2.24
0.28
1 14
9.99 3.81
2.61
0.12
34.31 80.60
1 7
34.31 11.51
2.97
0.12
0.02 6.53
1 6
0.02 1.08
0.02
0.87
Sum of squares
df
3.29 31.78
1 12
9.99 53.43
Mean square
CO us. A Groups Error CO vs. B Groups Error co
vs. c
Groups Error CO vs. D Groups Error
270
series and the control were not significant. Results were obtained using the 11 first values of the second period of Table I. Results using all the data were also non-si~ificant. DISCUSSION
The most striking finding of this study was that acupuncture, in the 4 sites explored, did not produce analgesia in the rabbit. In some isolated cases, the reaction time increased markedly during a few stimulations, only to return to the control level again, despite continuation of the acupuncture stimulation. These rabbits were responsible for the transient increase of the mean and the high standard deviations observed, particularly evident in series A and C. Repetition of the same schedule of stimulation after 2-15 days in these animals, which demonstrated a transient increase of their reaction time, failed to confirm the lengthening of the reaction time. In several animals which showed transient increases in their pain tolerance, we repeated the sessions of acupuncture changing the shape of the wave, and the intensity, frequency or duration of the acupuncture stimulation; we did not obtain analgesic effects. These experiments with a changed protocol were not included in the Tables I and II. We did not consider the transient lengthening of the reaction time as representative of acupuncture analgesia, which is characterized by a steady level of high pain threshold and pain tolerance; it appears after several minutes of acupuncture stimulation and maintains a stable intensity sufficient to permit surgical procedures; it lasts longer than the period of acupuncture stimulation, and then gradually fades 141. The occasional increase of pain tolerance observed in our experiments could be due to several factors, such as sleep, fatigue, fear, attention, learning, even transitory periods of animal hypnosis [ 1,6,12]. Some animals breathed fast and lifted the nose very fast, keeping it wet during the heat stimuli. Our results did not confirm the existence of the intense analgesic effect of acupuncture reported by Niboyet [9]. He used diazepam as premeditation, in an unspecified dose, and the animal appeared very hypnotonic in several pictures of Niboyet’s book. We do not know, therefore, if the reported analgesia was due to the effect of acupuncture alone. He did report neither a control series nor quantitative data. Rabischong et al. [ 111 reported acupuncture analgesia in 72% of their rabbits. They used a prick of the hind leg skin as painful stimulation and electrical stimulation of acupuncture needles in the hip (Tche-Pienn) and the calf (Tsou-Sann-Li). They did not report quantitative data. They also reported specific analgesia in the calf and thigh, and the transfer of the serum from these animals (donors) to control rabbits, produced analgesia confined to the same area as that of the donor. These results need to be confirmed with careful consideration to natural variations of pain sensibility in different areas of the skin. We cannot make inferences about pain in absolute terms. Nevertheless, on the bases of operational behavioral measurements, the acupuncture proce-
271
dure - as we did it - did not produce tolerance in rabbits.
significant
long-lasting
changes of pain
ACKNOWLEDGEMENTS
We wish to thank Dr. G.F. Brindle (Department of Anaesthesia, University of Sherbrooke) for comments on this manuscript and Mr. R. Black (Service d’Informatique, University of Sherbrooke) for the statistics. This research was supported by Grant 3-05-1511-1-0001-110-402-9 of the Ministere des Affaires Sociales. Dr. G.F. Brindle is the director of the research project. REFERENCES
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Carli, G., Farabollini, F. and Fontani, G., Responses to painful stimuli during animal hypnosis, Advanc. Pain Res. Ther., 1 (1976) 727-731. Chapman, CR., Measurement of pain: problems and issues, Advanc. Pain Res. Ther., 1 (1976) 345-353. Fogarty International Center, Acupuncture Anesthesia (a translation of a Chinese publication of the same title), DHEW Publication, NIH, Bethesda, Md., 1975, 339 pp. Kaada, B., Neurophysiology and acupuncture: a review, Advanc. Pain Res. Ther., 1 (1976) 733-741. Kaada, B., Hoel, E., Leseth, K., Nygaard-Ostby, B., Setekleiv, J. and Stovner, J., Acupuncture analgesia in the People’s Republic of China, T. norske Laegeforen., 94 (1974) 417-442. Keely, D.D. and Glusman, M., Emotional and psychological factors modifying the pain response of animals, Advanc. Pain Res. Ther., 1 (1976) 335-341. Marx, J.L., Analgesia: how the body inhibits pain perception, Science, 195 (1977) 471-473. Melzack, R. and Wall, P.D., Pain mechanisms: a new theory, Science, 150 (1965) 971-979. Niboyet, J.E.H., I’Anesthesie par l’Acupuncture, Maisonneuve, 1973, 433 pp. Pomeranz, B., Cheng, R. and Law, P., Acupuncture reduces electrophysiological and behavioral responses to ‘noxious stimuli: pituitary is implicated, Exp. Neural., 54 (1977) 172-178. Rabischong, P., Niboyet, J.E.H., Terral, C., Senelar, R. et Casez, R., Bases experimentales de l’analgesie acupuncturale, Nouv. Presse med., 4 (1975) 2021-2027. Segundo, J.P., Galeano, C., Sommer-Smith, J.A. and Roig, J.A., Behavioural and EEG effects of tones “reinforced” by cessation of painful stimuli. In: J.F. Delafresnaye (Ed.), Brain Mechanisms and Learning, Blackwell, Oxford, 1962, pp. 265-291.
