Acta Obstet Gynecol Scand 64:491-497, 1985
RELIEF OF PRIMARY DYSMENORRHEA BY
TRANSCUTANEOUS ELECTRICAL NERVE STIMULATION
Acta Obstet Gynecol Scand Downloaded from informahealthcare.com by (ACTIVE) Karolinska Institutet University Library on 03/20/11
For personal use only.
T. Lundeberg, L. Bondesson and V. LundstrOm
From the Department of Physiology II, Karolinska Institutet; the Department of Medicine, Danderyds sjukhus; and the
Department of Obstetrics & Gynecology, Karolinska sjukhuset, Stockholm, Sweden
Abstract. In this study we describe the use of high-frequency transcutaneous electrical nerve stimulation (TENS)(~OO
Hz) and low-frequency TENS (lf-TENS) (2 Hz trains) as
compared with placebo-TENS @-TENS) in a group of 21
patients suffering from primary dysmenorrhea. Naloxone, a
relatively pure opiate antagonist, was an additional test administered to 6 volunteer patients who had experienced an
alleviation of pain with TENS. As will be seen, 14 out of 21
patients receiving high-frequency TENS (hf-TENS) experienced a pain reduction exceeding 50% of its original intensity. During If-TENS or p-TENS, only 7 and 5 patients, respectively, obtained pain relief exceeding 50%. In 4 out of 6
volunteer patients, the relief of pain obtained with If-TENS
was counteracted by naloxone, whereas the relief experienced with hf-TENS in the same patients was, in general, unaffected by naloxone.
Key words: Dysmenorrhea, TENS, naloxone
have been used in the treatment of primary. dysme.
norrhea are hormonal preparations that inhibit ovulation (4, 5, 8, 24). However, a non-pharmacological
method for the alleviation of dysmenorrhea can be of
great value especially in patients suffering from various side effects from the drugs used. One of the most
widely used non-pharmacological methods for the
relief of pain is transcutaneous electrical nerve stimulation, TENS. In several studies this method has proved to be an effective measure against a number of
pain conditions of varying origin (3, 6, 7, 19, 22,26).
In this paper we describe the use of hf-TENS (100
Hz)and If-TENS (2 Hz trains; 6,7) as compared with
p-TENS in a group of 21 patients suffering from primary dysmenorrhea. Naloxone, a relatively pure
opiate antagonist, was an additional test administered
to 6 volunteer patients who had experienced an alleviation of pain with both hf-TENS and If-TENS.
Dysmenorrhea is a very common complaint, being
presented by about 10% of females in their late teens
and early twenties. The pain is often so severe that the
women has to stay in bed for one or two days, thereby often occasioning absence from work.
Evidence indicates that prostaglandins regulate
mvometrial contractility leading to ischemia. which
The study was performed on 21 patients suffering from primary dysmenorrhea who had been referred because of
symptomatic pain treatment. All of the patients complained
of pain localized to the lower back (bilaterally) during men-
strual fluid of dysmenorrheic women and the levels of
Also, 10 of the patients had to stay in bed for 2 days. All the
viating dysmenorrhea is related to their effectiveness
in depressing prostaglandin synthesis or its action.
ca2+antagonistic agents such as nifedipine
and 'erapami' have been shown to reduce prostaglandin-induced uterine hmercontractih', thereby
relieving menstrual pain (2, 9, 20). Other drugs that
meits. Furthermore, the patients were told that they might
or might not experience pain relief - or even exacerbated
pain during stimulation, but every effort was made to avoid
any suggestion as to the effect. The patients were told that
they could stop the stimulation treatment at any time. Their
history of pain ranged from 18 months to 9 years. The mean
age of the 21 patients was 22 years (15-29). All had previ-
MATERIAL AND METHODS
Acta Obstet Gynecol &and 64 (1985)
Acta Obstet Gynecol Scand Downloaded from informahealthcare.com by (ACTIVE) Karolinska Institutet University Library on 03/20/11
For personal use only.
492
T. Lundeberg et al.
ously undergone various therapies which had resulted in unsatisfactory alleviation of pain, or various side effects.
Before treatment, the patients were asked to describe the
location of their pain and its characteristic qualities, using a
modified McGill pain questionnaire (cf. 15). They were also
asked to describe drug intake, intake of alcohol, smoking
habits, physical activity levels, effects of the pain in relation
to daily behavior patterns and what made the pain increase
or decrease. The patients also rated their subjective pain intensity before each stimulation session using a visual analogue scale. The words “no pain” and “worst pain ever”
were placed at the left and right extreme end, respectively,
of a 10 cm long horizontal line. The patients were instructed
to mark the line at a point representing their pain. After
stimulation, the patients were again asked to rate their subjective pain intensity.
While receiving treatment with TENS or p-TENS the patients rated their subjective pain intensity using a mechanical device with a graphic rating scale, connected to an inkwriter out of sight of the patient (12, 18). No verbal communication took place with the patient during treatment.
Experimental protocol f o r treatment
The patients were randomly assigned to one of three groups,
each group consisting of seven patients. All patients were
treated during separate cycles with hf-TENS, If-TENS, or
p-TENS, making a total of two TENS sessions and one placebo treatment.
Treatment groups
Group 1 received If-TENS during the first trial, hf-TENS
during the second trial, and p-TENS during the last treatment cycle.
Group 2 received p-TENS during the first trial, If-TENS
during the second trial, and hf-TENS during the last treatment cycle.
Group 3 received hf-TENS during the first trial, p-TENS
during the second trial, and If-TENS during the last treatment cycle.
TENS in comparison with naproxen and verapamil
Following the end of the three different treatment cycles the
patients were asked during which cycle they experienced the
most effective pain alleviation. The type of stimulation used
during this cycle was termed the “mode of choice”. In the
next cycle the patients were given one treatment with the respective “mode of choice” stimulation. On the following
day, if pain persisted, they were given 500 mg naproxen and
asked to rate its effect on the visual analogue scale. Finally
the patients were asked to compare the effect of naproxen
with that of the “mode of choice” stimulation. The same
procedure was repeated during the next cycle, with the difference that the patients were given 120 mg verapamil instead of naproxen.
Effect of naloxone
Naloxone hydrochloride was given intravenously in a 0.4
mg/ml solution. In 4 patients, two test injections of 1.0 mg
were first administered while experiencing alleviation of
pain from treatment. If the pain returned within 10 min, a
double-blind experiment was always performed with a series
of six intravenous injections at 30-min intervals. In 2 paActa Obstet Gynecol Scand 64 (1985)
tients, however, the double-blind procedure was performed
directly. Sterile saline of the same volumes was used as placebo. The pain intensity was scored continuously on the graphic rating scale. Changes in pain intensity of less than 10%
10 min after injection were considered uncertain (cf. 22).
High-frequency TENS
The TENS apparatus used (Electroform 4C) produced
monopolar square wave pulses with a duration of 0.2 msec
and a frequency of 100 Hz. A pair of rubber electrodes,
each with a surface area of 36 cm2, were applied to the skin
in the painful area. The stimulus intensity was just below
the pain treshold (low intensity). At the first treatment session, TENS was applied to the area of pain for 20 min. If a
pain-relieving effect was obtained, the treatment was continued for a further 25 min at the same point. If the patient
did not report a reduction of pain after 20 min of treatment
the electrodes were moved to some other place, e.g. a trigger
point, if this was localized outside of the area of pain, proximal to the area of pain, along the peripheral nerve or to an
acupuncture point close to the area of pain. If no reduction
was obtained at any of these points the electrodes were applied for 25 min within the painful area (16).
Low-frequency TENS
The TENS apparatus used (Electroform 4C) produced
trains of monopolar square wave pulses with a duration of
0.2 msec. Each pulse train (8 pulses) had a total duration of
80 msec and was delivered at 2 trains per second (2 Hz).The
intensity used produced muscular contractions in the stimulated area (high intensity). The electrodes used, their placement and the procedure used were the same as for hf-TENS.
Placebo
Placebo-TENS was performed using the same type of apparatus as during TENS treatment, but the apparatus had no
electrical output to the electrodes. The patients were told
that they were given an “ultra-high frequency” TENS treatment and that some people may not experience any cutaneous sensations during stimulation.
RESULTS
The McGill Pain Questionnaire
The McGill pain questionnaire was used as a means
of assessing the pain profile of patients suffering
from dysmenorrhea. Factorial investigations of the
questionnaire provided for a distinction between affective and sensory descriptors (dimensions). Fortythree per cent of the patients checked words (fearful - terrifying and wretched - blinding), describing
emotional or affective aspects of the pain, which may
reflect the negative attitude held by many women towards their period pains. Sixty-eight per cent of the
patients checked sensory descriptors. Two components of sensory descriptors were derived - one related to dullness, and the other to cramping. In conclusion the pattern of scores emerging from the ques-
Electrical nerve stimulation for dysmenorrhea
493
Table I. Mean pain intensity scores before treatment
sessions.
Acta Obstet Gynecol Scand Downloaded from informahealthcare.com by (ACTIVE) Karolinska Institutet University Library on 03/20/11
For personal use only.
PLACEBO-TENS
Treatment
session
Group
1
2
3
I
I1
111
IV
V
VI
VII
4.6
4.4
4.9
5.1
4.2
4.7
3.1
5.2
3.1
4.5
4.1
3.8
4.2
5.1
3.9
5.1
3.9
4.3
4.6
4.9
3.9
tionnaire indicate the significance of the emotional or
affective aspect of the pain.
Pain intensity score
As indicated in Material and Methods all patients
were asked to rate their pretreatment pain on a visual
analogue scale. The mean pain intensity score of the
three groups is given in Table I. As seen, there was no
significant difference between the three groups.
Site of stimulation
Eighteen of the patients reported that the best point
of stimulation was the painful area on the back
(Thl0-L1). Three patients reported that the best site
was located on the abdomen (segmentally related to
the painful area).
Pain-reducingeffect of peripheral stimulation
The diagrams in Fig. 1 summarize the effects of the
different modes of stimulation used in the present
study. As can be seen, TENS stimulation at 100 Hz
(high frequency) (hf-TENS) was clearly superior to 2
Hz TENS (low frequency) (If-TENS) or placeboTENS @-TENS).
LOW TENS
HIGH TENS
a
Fig. 2. Number of patients obtaining relief of pain from hfTENS, If-TENS, and p-TENS.
When treated with hf-TENS stimulation, 16 out of
21 patients experienced relief of pain. Increased pain
was experienced by 3 patients, and 2 patients reported
no change in pain intensity.
Of all 21 patients, 9 women obtained a reduction of
their pain with If-TENS. Low-frequency TENS caused an increase in pain in 3 patients and left 9 patients
unaffected by the treatment.
During placebo ‘stimulation’ 7 patients experienced pain alleviation, while 14 patients obtained no reduction in pain. Out of these 14 patients, 3 women reported an increase in pain. It is interesting to note
that the same 3 patients also reported an increase in
pain during TENS stimulation.
The diagram in Fig. 2 summarizes the effect of the
various TENS modes of treatment and placebo, the
numbers in the circles indicating the number of patients experiencing pain relief for each mode of treatment and placebo. In all, 17 of the 21 patients experienced pain relief; 8 of these patients experienced a re30
EFFECT OF TENS OR PLACEBO-TENS TREATMENT
HIGH TENS
LOW TENS
PLACEBO-TENS
0
+
0 50100%
+
0 50100%
+
0 50100%
Fig. I . Effects of TENS and p-TENS on subjective pain intensity. Pain increase (+), no changes in pain intensity (0),
pain reduction 50% or less (50), pain reduction 50- 100%
(100); hatched area, complete relief of pain.
10
20
30
k0
310
320
330
340
350
TIME (MIN)
Fig. 3. Effect of hf-TENS in a 19-year-old patient. TENS
applied for 45 min in the painful area. Abscissa: time, in
minutes; ordinate: subjective pain intensity; zero indicates
pain intensity before hf-TENS. Downward deflection, pain
reduction, 100% indicating complete relief of pain.
Acto Obstet Gynecol Scand 64 (198s)
T. Lundeberg et al.
494
INDUCTION TIME FOR MAXIMAL PAIN REDUCTION
MlGH TENS
Ln
LOW TENS
PLACEBO-TENS
Acta Obstet Gynecol Scand Downloaded from informahealthcare.com by (ACTIVE) Karolinska Institutet University Library on 03/20/11
For personal use only.
lo
0 1 0 20 30 40
i
0 10 20 30 40
0 10 20 30 40
TIME IMIN)
Fig. 4. Induction time for maximal pain reduction in the patients experiencing pain relief.
duction of pain with both modes of stimulation; 5 out
of these patients also experienced a reduction of pain
during p-TENS. High-frequency TENS relieved the
pain in about 70% of the patients, whereas If-TENS
and p-TENS relieved about 45% and 33%, respectively. In all, 16 out of the 21 patients (75%) experienced pain relief with peripheral stimulation. Five of the
21 patients obtained no reduction of pain with TENS.
However, one of them was relieved from pain by
placebo.
Induction time for pain relief
The time course of the pain-suppressive effect was
measured in all patients from the records obtained by
graphic rating (see Material and Methods). One such
record is presented in Fig. 3. The patient was a
19-year-old woman who had been suffering from dysmenorrhea for 2% years. The pain was localized to
the lower back. High-frequency TENS was applied
within the painful area. The time required for the first
sign of pain reduction to appear in this patient was 2
min, and 11 min for the maximal pain reduction obtained. In this patient the maximum pain reduction
obtained was 100% (complete relief of pain). However, among the patients experiencing pain relief, the
maximum pain reduction obtained varied between 10
and 100%.
The data obtained from measurements of the time
necessary for maximum pain suppression from the records as illustrated in Fig. 3 are summarized in Fig. 4.
As seen, approximately the same time for stimulation
was required for If-TENS and p-TENS in order to obtain maximal pain suppression. On average, pain was
completely suppressed with these modes of stimulation within 20-25 min. High-frequency TENS had in
general a faster pain-suppressing effect, pain relief
being obtained in most patients after about 10 min.
Duration of pain relief
It is well known that TENS treatment can produce
pain suppression which sometimes lasts for several
hours. It was therefore of interest to measure the duration of effect of the two types of TENS and
p-TENS in the present study. As seen in Fig. 5 , there
is no significant difference in this respect between the
different modes of TENS or p-TENS.
Comparison with naproxen and verapamil
The results of the comparison of the pain-alleviating
effect of “mode of choice” stimulation as compared
with naproxen or verapamil are presented in Table 11.
Out of 17 patients experiencing pain relief, 5 patients
treated with hf-TENS rated the pain-relieving effect
of stimulation (“mode of choice”) as better than that
of naproxen. Four of the patients, 2 women treated
with hf-TENS (“mode of choice”) and 2 treated with
If-TENS (“mode of choice”) reported that naproxen
and the “mode of choice” were about equally effective in relieving their pain. Eight patients, 6 of whom
treated with hf-TENS (“mode of choice”), one patient treated with If-TENS (“mode of choice”), and
one patient with p-TENS (“mode of choice”) rated
500 mg of naproxen as most effective. Four out of the
5 patients who did not obtain relief of pain when
treated with TENS reported pain relief from taking
naproxen. Out of 17 patients experiencing pain relief,
7 (6 treated with hf-TENS and one patient treated
DURATION O F RELIEF
HIGH TENS
In
W
z
F
n
%
a
m
s
z
10
5
PLACEBO-TENS
LOW TENS
t
i
10
1,
I
5
O-V2 v2-3
3-6
6-12
10
>lZ
Acto Obstet Gynecol Scand 64 (198s)
-
00
>12
6-12
>12
Fig. 5. Duration of pain relief
after treatment.
Electrical nerve stimulation for dysmenorrhea
495
Table 11. Comparison of “mode of choice” stimulation vs. naproxen and vs. verapamil.
No. of
pats.
“Mode of choice”
stimulaton
13
High TENS
Low TENS
Placebo-TENS
Acta Obstet Gynecol Scand Downloaded from informahealthcare.com by (ACTIVE) Karolinska Institutet University Library on 03/20/11
For personal use only.
3
1
2
2
5
Effect of naloxone
During the previous treatment cycles the 6 volunteer
patients had experienced relief of pain with both
high- and low-frequency TENS. During the additional cycles they were treated with hf-TENS or If-TENS
and subjected to naloxone. The results from the 6 patients when receiving hf-TENS and naloxone can be
seen in Fig. 6 . Here the patients’ reactions to test
doses of naloxone are denoted by open circles and the
reactions to saline or naloxone administered in
double-blind fashion are illustrated as filled circles.
Equal
Poorer
6
6
4
3
1
1
1
1
INHIBITION
YES
-
UNCERTAIN
-
NO
1
The reactions to saline are shown in the left part of
the diagram and those to naloxone are shown on the
right-hand side. It can be seen that none of these patients consistently experienced any inhibition of pain
reduction from naloxone. However, one patient (No.
3) reported inhibition of pain alleviation from four
out of six injections, containing either saline or naloxone. In Fig. 6 the corresponding results are shown for
If-TENS treatment. Patients 1, 2, 4, and 5 systematically experienced inhibition of pain relief from naloxone, but not from saline. Patient No. 3 indicated inhibition of pain alleviation both from naloxone and
saline administration. Patient No. 6 , on the other
hand, did not experience any changes in the pain
relief after If-TENS from naloxone or saline injections.
DISCUSSION
Transcutaneous electrical nerve stimulation has been
extensively used in recent years for the relief of a
variety of pain syndromes. Although it has been
known that TENS can effectively suppress pain, this
method appears not to have been widely used in clinical practice for the alleviation of dysmenorrhea.
However, recent observations on the pain-suppressive effect of hf-TENS in patients suffering from dys-
INFLUENCE OF NALOXONE
hf-TENS and with If-TENS.
Reactions to saline (NaCI)
and naloxone given separately
for each patient. Inhibition of
pain relief scored on the
graphic rating scale and described in Methods.
Better
1
with If-TENS) rated the pain-relieving effect of stimulation (“mode of choice”) as more pronounced
than that of verapamil. Six of the patients, 4 women
treated with hf-TENS (“mode of choice”), one woman with If-TENS (“mode of choice”) and one with
p-TENS (“mode of choice”) reported that verapamil
and the “mode of choice” were about equally effective in relieving their pain. Four patients, 3 of whom
were treated with hf-TENS (“mode of choice”) and
one treated with If-TENS (“mode of choice”) rated
120 mg of verapamil as most effective. Two out of the
5 patients who did not obtain any relief of pain when
treated with TENS reported pain relief when taking
verapamil .
Fig. 6. Influence of naloxone
on pain relief obtained with
Compared wih verapamil
Compared with naproxen
Better
Equal
Poorer
- INHIBITION OF PAIN RELIEF
INHIBITION
-
YES
.. .. .. .. .........
............
0
0
0
0 0 0
0
0
UNCERTAIN
NO
’
-
.....
.....
.....
0
0
0 0 0 0
......
...
......
0
D O
I
,
I
I
I
I
PATIENT NO.
1 2 3 4 5 6
NOlOlonb
Acta Obstet Gynecol Scand 64 (198s)
Acta Obstet Gynecol Scand Downloaded from informahealthcare.com by (ACTIVE) Karolinska Institutet University Library on 03/20/11
For personal use only.
496
T. Lundeberg et ai.
menorrhea have focused attention on this mode of
treatment as an alternative pain-alleviating measure
in dysmenorrhea (13).
In the present study we have compared the pain-reducing effects of hf-TENS, If-TENS and p-TENS
with that of naproxen and verapamil. Each patient
was subjected in random order to the various TENS
modes of treatment. About 70% of the patients experienced pain reduction when treated with hf-TENS.
Low-frequency TENS was clearly less effective and
relieved only about 45% of the patients. Moreover,
even though 9 out of the 21 patients experienced pain
relief from If-TENS, only 3 rated it as “mode of
choice”. This would seem to imply that the pain relief
scores should be interpreted with caution as to which
mode of treatment to use. In all, about 75% of the
patients (16 women) reported that they experienced
some relief of pain during one or several of the sessions of peripheral stimulation. Of these 16 patients,
5 treated with naproxen and 7 treated with verapamil
rated TENS as more effective than naproxen/verapamil, whereas 8 patients treated with naproxen and 4
patients with verapamil rated the effect of naproxedverapamil as superior to TENS. This would appear to suggest that in the choice between naproxen
and verapamil the latter mode of treatment is to be
preferred for the treatment of dysmenorrhea. Howver, TENS appears to be more effective than verapamil in relieving patients from dysmenorrhea and
about equally effective with naproxen. This would
appear to suggest that TENS can be used for the
symptomatic treatment of dysmenorrhea and especially in patients suffering from the side effects of the
drugs used. In the choice of treatment of dysmenorrhea, both hf-TENS and naproxen and verapamil
therefore merit consideration. Also,TENS can be administered by paramedical personnel once the appropriate point or area of stimulation has been located and can even be self-administered by the patients.
The present results indicate that a non-opioid pathway mediates the relief of pain obtained with hfTENS, whereas the relief of pain obtained with lfTENS appears to involve endogenous opioids. This is
in agreement with previous results of SjOlund &
Eriksson (22). On what basis then is the pain-suppressive effects obtained by hf-TENS? Since the presentation of the gate control theory, the neurophysiological basis of the theory has been questioned. Still, evidence is available (10) that activity in pain-carrying
fibers is subjected to modulation from other sensory
inputs and from descending influences from supraActa Obstet Gynecol Scand 64 (1985)
spinal areas. Furthermore, there is increasing evidence that non-opioid pathways, especially descending
serotonergic pathways, suppress pain in animals (1,
11, 21, 25).
ACKNOWLEDGEMENTS
The authors are greatly indebted to Dr David Ottoson for
his unfailing help and valuable criticism during this study.
The technical assistance of Ms Ulla Lindgren is greatly
acknowledged. This work has been supported by grants
from the funds of Karolinska Institutet. The study was approved of by the Ethics Committee of Karolinska Institutet
and all patients gave informed consent to take part in the
study.
REFERENCES
1 . Akil H, Mayer DJ. Antagonism of stimulation-produced analgesia by p-CPA, a serotonin synthesis inhibitor.
Brain Res 1972;44:692- 7.
2. Anderson K-E, Ulmsten U. Effects of nifedipine on
myometrial activity and lower abdominal pain in women with primary dysmenorrhea. Br J Obstet Gynaecol
1978;85:142- 8.
3. Augustinsson L-E, Bohlin P, Bundsen P, Carlsson
C-A, Forssman L, SjBberg P, Tyremann NO. Pain relief during delivery by transcutaneous electrical nerve
stimulation. Pain 1977;4:59-65.
4. Aydar CK, Coleman BP. Treatment of primary dysmenorrhea: a double blind study. J Amer Med Ass 1965;
192:1OO3 - 5 .
5 . Bishop PMF. A new oral progestogen in the treatment
of dysmenorrhea. Proc Roy SOCMed 1961;54:752-4.
6. Eriksson MBE, Sjolund BH. Acupuncture-like electroanalgesia in TENS-resistant chronic pain. In Sensory
Function of the Skin (Ed. Zotterman Y), pp. 575-81.
Pergamon Press, Oxford and New York, 1976.
7. Eriksson MBE, SjBlund BH, Nielzen S. Long term results of peripheral conditioning stimulation as an analgesic measure in chronic pain. Pain 1979;6:335-47.
8. Fdrin J. Hypoestrogenic amenorrhea and/or sterility
induced by lynestrenol. Int J Fertil 1964;9:29- 34.
9. Fleckenstein A, Griin G. Reversible Blockierung der
elektromechanischen Koppelungsprozesse in der glatten
Muskulatur des Rattenuterus mittels organischer Ca2 Antagonisten (Ipoveratril, D - 600, Prenylamin). Pfluegers Arch 1969;307:1226.
0. Handwerker HO, Iggo A, Zimmerman M. Segmental
and supraspinal actions on dorsal horn neurons responding to noxious and non-noxious skin stimuli. Pain 1975;l :147 - 65.
1 . Hosobuchi Y. Tryptophan reversal of tolerance to analgesia induced by central gray stimulation. Lancet
1978;ii:47.
2. Lundeberg T. Vibratory stimulation for the alleviation
of chronic pain. Acta Phys Scand 1984;Suppl. 523:
1-51.
3. Lundeberg T, L u n d s t r h V. Transcutaneous electrical
nerve stimulation (TENS) in primary dysmenorrhea.
Int Symp September 1983.
+
Acta Obstet Gynecol Scand Downloaded from informahealthcare.com by (ACTIVE) Karolinska Institutet University Library on 03/20/11
For personal use only.
Electrical nerve stimulation for dysmenorrhea
497
14. LundstrBm V, Green K. Endogenous levels of prosta-
23. Sjdlund B, Terenius L, Eriksson M. Increased cerebro-
glandin F, and its main metabolites in plasma and endometrium of normal and dysmenorrheic women.
Amer J Obstet Gynecol 1978;130:640-6.
15. Melzack R. The McGill Pain Questionnaire: Major
properties and scoring methods. Pain 1975;I :277 - 99.
16. Melzack R. Prolonged relief of pain by brief intense
transcutaneous electrical stimulation. Pain 1975; 1 :
spinal fluid levels of endorphins after electroacupuncture. Acta Physiol Scand 1977;100:383-4.
24. Sturgis SH, Albright F. Mechanism of estrogen therapy
in relief of dysmenorrhea. Endocrinology 1940;26:
68 - 72.
25. Vogt M. The effect of lowering the 5-hydroxytryptamine content of the rat spinal cord on analgesia produced by morphine. J Physiol, London 1974;236:
357-73.
17. Nathan PW. The gate control theory of pain. A critical
review. Brain 1976;99:123 - 58.
18. Ottoson D, Ekblom A, Hansson P. Vibratory stimulation for the relief of pain of dental origin. Pain 1981;
10:37 - 45.
19. Ray CD. Control of pain by electrical stimulation. A
clinical follow-up review. In Advances in Neurosurgery, Vol. 3, pp. 216-24. (Eds. Penzholz H et al.).
Springer Verlag, Heidelberg, 1975.
20. Reiner 0, Marchall JM. Action of prostaglandin,
PGF,,, on the uterus of the pregnant rat. Naunyn
Schmiedebergs Arch. Pharmacol 1976;292:243 - 50.
21. Saarnivara L. Effect of 5-hydroxytryptamine on morphine analgesia in rabbits. Med Exp Fenn 1969;47:
113-23.
22. SjBlund B, Eriksson M. The influence of naloxone on
analgesia produced by peripheral conditioning stimulation. Brain Res 1979;173:295- 301.
483 - 98.
26. Wall PD, Sweet H. Temporary abolition of pain in
man. Science 1967;155: 108 - 9.
27. Ylikorkala 0, Dawood MY. New concepts in dysmenorrhea. Amer J Obstet Gynecol 1978;130:833 -47.
Submitted for publication March I , I984
Accepted June 21, I984
Lundeberg T, M.D.
Department of Physiology I1
Karolinska Institutet
104 01 Stockholm 60
Sweden
Acta Obstet Gynecol S a n d 64 (1985)