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CSF monoamine metabolites in chronic pain
189
Pain, 31 (1987) 189-198 Elsevier
PA1 01107
CSF monoamine metabolites in chronic pain
Clinton
’
Randal D. France *, Bruno J. Urban * * , Susan Pelton * , D. Kilts * , Jau-Shyong Hong * * * and Charles B. Nemeroff
*
Departments of * Psychiatry and * * Anesthesiology, Duke University Medical Center, and * * * Laboratoty of Behavioral and Neurological Toxicology, National Institute ofenvironmental Health Services, Durham, NC (U.S.A.) (Received
22 January
1987, revised received and accepted
2 April 1987)
summary
Metabolites of selected neurotransmitters (5-H&A, HVA and DOPAC) and beta-endorphin were measured in the CSF of 39 chronic pain patients and compared to controls. Twelve of the pain patients also fulfilled criteria for major depression. The con~ntration of 5-HIAA was increased in female but not male pain patients; there was no significant difference in the CSF concentrations of HVA and DOPAC. The presence of depression did not influence the concentrations of nemotransmitters. No correlation was found between the concentrations of monoamine metabolites and beta-endorphin. However, there was a positive correlation between 5-HIAA and HVA in controls and chronic pain patients without depression but not in depressed patients. It is concluded: chronic pain states are associated with elevation of CSF 5-HIAA in female patients; depression abolishes a positive correlation between 5-HIAA and HVA. Key words: Neurotransmitters;
Depression;
CSF; Chronic
pain states
Intmduetion
Many chronic pain states are characterized by a pain complaint out of proportion to evidence for ongoing nociception and by affective and behavioral responses which may often progress to a psychiatric illness. Indeed, it has been proposed that clinical depression inv~ably follows chronic pain [8,24]. Both, pain and depression, are thought to be associated with alterations of endogenous opioid substances and biogenic amines in the central nervous system
’ Monoamine metabolite analysis MH-4019 and AG-05128.
was partially
supported
by NIMH
Correspondence to: Randal D. France, M.D., Assistant Medical Center, Box 3903, Durham, NC 27710, U.S.A.
03043959/87/$03.50
0 1987 Elsevier Science Publishers
Professor
Grants
MH-40542,
of Psychiatry,
B.V. (Biomedical
Division)
Duke
MH-39415,
University
190
(CNS). There is evidence that opioid-like substances excite specific neural structures which in turn produce antinociception by inhibiting transmission of noxious evoked impulses at the spinal level. A negative feedback loop of endogenous pain control has been postulated involving various neurotransmitters, most notably serotonin and norepinephrine [7]. The same endogenous opioid substances and neurotransmitters have also been reported to be altered in depression [3,17]. The elevated pain threshold in certain depressed patients has been linked to elevated concentrations of endorphins [lo]. Subtypes of depression have been associated with CNS deficiencies in serotonin and norepinephrine [21]. Studies of CNS biogenic amines in chronic pain patients are scanty and equivocal. One group reported elevated concentrations of cerebral spinal fluid (CSF) 5-hydroxyindoleacetic acid (5-H&4), a metabolite of serotonin in chronic pain patients but also in patients with acute pain [13]. There was no relationship between concentrations of 5-HIAA and pain or degree of depressive symptomatology. Another group described a wide variation in CSF 5-HIAA concentrations which were interpreted as ‘abnormal’ and ‘skewed towards lower levels’ [2]. There was no difference in CSF levels of 5-HIAA and homovanillic acid (HVA), a metabolite of dopamine, between patients with ‘organic’ pain and those with ‘psychogenic’ pain. A positive correlation was reported between CSF 5-HIAA and fraction I endorphins, an uncharacterized opioid. Neither study utilized concomitant controls. The paucity and discrepant nature of these data prompted us to investigate CSF monoamine metabolites in chronic pain patients and explore their relationship to beta-endorphin and depression.
Methods Description of patients A total of 39 patients (14 male, 25 females; mean age: 44 years, range 29968 years) with chronic low back pain/sciatica were studied. They had failed to improve with extensive medical and surgical treatments. They had undergone an average of 2.4 + 1.4 (range O-7) operations for their pain complaint. All patients experienced continuous daily pain for at least 6 months (mean 73.9, range 6-24 months). Severity of pain as measured by the mean total McGill Pain Questionnaire [18] score was 35.8 + 12.5 (range 14-73). Medical evaluation provided evidence of neurological dysfunction explaining location but not intensity of pain; there was no indication for further etiological treatment. Psychiatric evaluation by structured interview arrived at the diagnosis of Major Depressive Disorder (MDD) in 12 patients (31%). The remainder were diagnosed as No Diagnosis, Somatoform Disorder, Dysthymic Disorder or Adjustment Disorder (DSM-III criteria [4]). Since MDD has biological components which the other diagnoses lack, we felt justified in grouping these latter diagnoses together under the heading of No MDD. In no case was there evidence of Dementia, Personality and Substance Abuse Disorders, or obvious secondary gains.
191
Controls Twenty-two patients (9 male, 13 females, mean age: 25.9 years, range: years) free of chronic pain and MDD who underwent elective operation spinal anesthesia served as controls.
20-39 under
CSF sampling CSF samples were obtained after the pain patients had been free of psychoactive medications for a minimum of 1 week. With the patient in the lateral position, a spinal tap was performed at the L,_, or L,-, interspace. Sampling was performed in pain patients between 11.00 and 14.00 h, and at various times during the day in controls. Five ml of CSF were collected passively in 1 ml aliquots and immediately stored at -70°C. CSF was always clear and without evidence of contamination with blood. CSF analysis CSF concentrations of 5-H&%, HVA and DOPAC (3,4_dihydroxyphenylacetic acid), another metabolite of dopamine, were determined in the first aliquot by on-line tracer enrichment high performance liquid chromatography (HPLC) with electrochemical detection. To 500 ~1 aliquots of CSF was added 5 ~1 concentrated glacial acetic acid and 10 ng of 5-hydroxyindole-2-carboxylic acid (5-HICA, 5-HICA internal standard). Following centrifugation (10,000 X g for 5 min at 4” C) the entire sample was injected into the HPLC apparatus. The DOPAC, HVA, 5-HIAA and 5-HICA were on-line enriched on short octadecyl bonded HPLC enrichment columns (4 (I.D.) x 30 mm, Alltech Ass., Dearfield, IL) and subsequently separated by anion exchange HPLC (4 X 250 mm, SAX on 5 pm microparticulate silica, Chromanetics, Kensington, MD). The enrichment mobile consisted of 0.075 M KH PO (pH 3.0) and the analytical mobile phase consisted of 0.075 M KH PO (pH 4.5) with 5% acetonitrile. Both mobile phases were degassed by vacuum filtration and ultrasonic agitation prior to their isocratic delivery at 1.25 ml/mm. DOPAC, HVA, 5-HIAA and 5-HICA were detected amperometrically following electrochemical oxidation at a glassy carbon working electrode potential of +750 mV vs. an Ag/AgCl reference electrode (Bioanalytical Systems, Inc., Lafayette, IN). Calibration curves were generated by assaying 500 ~1 volumes of artificial CSF to which varying amounts (0, 2-40 ng) of DOPAC, HVA and 5-HIAA and a fixed amount (10 ng) of 5-HICA were added. The concentrations of DOPAC, HVA and 5-HIAA in human CSF samples were calculated from their peak height ratio relative to 5-HICA, using the slope and intercept of the appropriate calibration curve. Samples from pain patients and controls were analyzed concomitantly. In 21 patients, CSF was also analyzed for beta-endorphin using a radioimmunoassay described in detail elsewhere [15]. Prior to RIA, proteins were separated by a microbandpak CA,, column. The method has a 100% cross-reactivity with beta-lipotropin, less than 0.01% with enkephalins and is without a detectable cross-reactivity with dynorphin. The absolute sensitivity of the assay is 1 pg per tube; the interassay reliability is less than 5%.
192
Data analysis Statistical analyses were performed with non-parametric and parametric tests (~uskal-Wallis and ANOVA, corrected alpha level using Bonferroni correction followed by post hoc test using Tukey). Correlations were analyzed by Spearman’s rank correlation test. Beta-endorphin data were only used for correlational analysis and intergroup comparison since simultaneous control data were not available. We applied multivariant analysis (MANOVA) when looking at the influence of gender and depression (MDD, No MDD).
Results
Patients and control groups were not significantly different in regard to gender, height and weight. There was a significant difference (P = 0.0001) between the mean ages of patients (44.2 + 10.6 years) and controls (26.9 * 5.3 years). There was no significant correlation between monoamine metabolites and age, height, and weight in patients or in controls. This held true when controlling for gender in both groups and for MDD and gender in the patient group. 5-HIAA was significantly higher in pain patients than in controls regardless of presence or absence of MDD. There was no significant difference in CSF levels of HVA and DOPAC between patients and controls (Table I). There was a large spread in values for DOPAC, with the majority of determinations (19 for controls and 26 for patients) approaching or falling below the analytic sensitivity of the method. For this reason, we decided to forego further statistical analysis of the DOPAC results. Influence of gender and clepression When analyzing the pain and control groups separately, 5-HIAA was significantly higher in all female pain patients when compared with male pain patients (Table II). There was no gender difference in the control groups (Table II). HVA levels were generally evaluated in females. This elevation was only significant when comparing female pain patients with male pain patients (Table III). Again, there was no gender difference in the control groups.
TABLE
i
CSF MONOAMINE
METABOLITES
All pain patients
IN CHRONIC
PAIN
22.6+
HVA DOPAC
40.1+ 18.89 1.4+ 2.49
8.46
PATIENTS P
Groups
5-HIAA
* P -z 0.05 (Tukey).
@g/m{)
1. Pain with MDD
2. Pain with no MDD
23.0+
22.Si
7.54
43.4 * 15.40 1.21 1.84
8.97
38.7 i 20.35 1.5+ 2.76
3. Controls l&3*
5.05
32.0 i 10.55 0.6i 1.44
0.01 NS NS
ANR
CONTROLS
Group
comparisons
l-2
2--3
1-3
*
*
193 TABLE
II
5-HIAA (q/ml): ANALYSIS AGNOSTIC GROUPS
OF
VARIANCE
Male (jzk S.D.) 17.2+5.07 n=14 17.4 f 2.55 n=3 17.2 f 5.67 n=ll 15.3*5.74 n=9
Total pain patients Pain with MDD Pain no MDD Controls
TABLE
ANALYSIS
Total pain patients Pain with MDD Pain no MDD Controls
CONTROLLING
FOR
Female (X+S.D.)
KruskalWaIIis (P)
ANOVA
25.6 + 8.54 n = 25 24.8 f 7.82 n=9 26.1 f 8.13 n=16 17.0 f 4.6 n=13
0.002
0.0018
NS
NS
0.008
0.008
NS
NS
DI-
(P)
OF VARIANCE
ACROSS
GENDER
CONTROLLING
FOR
DIAGNOS-
Male (X f SD.)
Female (X+S.D.)
KruskaIWallis (P)
ANOVA
31.7 n=l4 36.6 n=3 30.3 n=ll 29.9 n=9
f 13.75
44.9 + 19.32 n = 25
0.03
0.034
f 19.02
45.7 f 14.59 n=9
NS
NS
f 12.80
44.47 f 27.83 n=16 33.7+ 9.42 n=13
NS
NS
NS
NS
f 12.1
(P)
IV
5-HIAA (ng/ml): FOR GENDER
ANALYSIS
OF VARIANCE
ACROSS
Pain patients 1. MDD (X f S.D.)
2. No MDD (X f S.D.)
3. Controls (X+ S.D.)
Total pain patients
23.0 f 7.54 n=12
22.5 f 8.97 n = 27
Male
17.4*2.55 n=3 24.8 + 7.82
17.2 + 5.67 n=ll 26.lk9.13
16.3 n = 15.3 n=9 17.0
n=9
n=16
n=13
Female
GENDER
III
HVA (ng/ml): TIC GROUPS
TABLE
ACROSS
* P < 0.05 (Tukey).
DIAGNOSTIC
GROUPS
KruskalWallis (P)
ANOVA
(P)
f 5.05 22 + 5.74
-
0.01
NS
NS
f 4.62
0.006
0.007
CONTROLLING
Group
comparisons
l-2
2-3
1-3
*
*
*
194
VVIH-9
VVIH-S
VVIH-S
VVIH-S
195
When comparing across gender and controlling for diagnostic groups (MDD, No MDD), 5-HIAA remained significantly elevated in female pain patients without MDD when compared to male pain patients without MDD (Table II). A similar comparison between male and female pain patients with MDD showed a difference of similar magnitude that was not statistically significant. There was no interaction between diagnostic groups and gender. In contrast, the earlier differences found in HVA levels between male and female pain patients were no longer significant when controlling for diagnostic groups and comparing across gender. We further investigated the influence of MDD on 5-HIAA by comparing pain patients with and without MDD to controls of the same sex (Table IV). S-HIAA in male patients with MDD was not significantly different from male patients without MDD or from male controls. In female pain patients, 5-HIAA was significantly elevated in patients without MDD compared to female controls. In female patients with MDD, a similar elevation of 5-HIAA was not significant. Correlations Correlational analysis demonstrated a significant positive relationship between 5-HIAA and HVA (r = 0.62, P = 0.002) for the control group (Fig. 1). When controlling for gender, this relationship failed to reach significance in female controls although the slopes were similar. All pain patients combined showed a strong positive correlation between 5-H&4 and HVA (r = 0.55, P = 0.0003). When controlling for gender and MDD, this correlation was only seen in chronic pain patients, male or female, without MDD. In depressed patients, this relationship did not hold (Fig. 1). Beta-endorphin did not correlate with 5-HIAA and HVA in pain patients. This also held true when controlling for gender or MDD. There was no difference in beta-endorphin between patients with and without MDD. Likewise, there was no gender difference in pain patients without MDD; the number of patients with MDD was too small for meaningful gender comparison.
Discussion Neurotransmitters have been located throughout the neuraxis; beta-endorphins and dopamine more in supraspinal levels while serotonin had been found in spinal locations as well. Chemical analysis of CSF for these substances is thought to reflect CNS changes [14]; alterations have been described in pain patients and depressives. The mechanism for interaction of neurotransmitters and reason for change are unknown. Nevertheless, neurochemical analysis may be used to correlate with treatment effect [l]. Alterations of CNS neurotransmitters in chronic pain patients may be an independent phenomenon or they may occur as a reaction to pain. Changes in CSF biogenic amines have previously been reported to occur in deviant behaviors. Abnormally low concentrations of 5-HIAA were observed in depressed and non-depressed patients who had attempted violent suicides; concentrations of HVA were
196
also lowered but only in the depressed patients [20]. These data were interpreted as reflecting a possibly genetically increased vulnerability to a range of psychiatric disturbances and to suicidal behavior. In a similar manner it is conceivable that a chronic pain state is more likely to occur in patients who are biologically susceptible. This hypothesis would explain the occurrence of a chronic pain syndrome in a subgroup of patients while other patients with a similar medical condition undergo uneventful recovery. It would further explain the high incidence of major depression in chronic pain patients and the positive response of both conditions to antidepressants [11,22]. From the literature, CNS biogenic amines seem the most likely substances to reflect abnormalities associated with pain and depression. In this study, we tried to minimize the effects of other variables on CSF biogenic amines. All patients were free of psychoactive medications. To control for diurnal variation and for a gradient of CSF metabolites within the spinal fluid column, we performed spinal taps at the same time of day, at the same interspace, and with the patient in the same position. We found no correlation between monoamine metabolites and weight, age, or height in pain patients and controls: these latter two findings are in contrast to the literature [5]. We did find that chronic pain patients show a general elevation in concentrations of CSF 5-HIAA regardless of the presence or absence of major depression. This confirms previous observations [13]. However, when analyzing our data across gender we found elevated levels of CSF 5-HIAA only in female patients. CSF 5-HIAA levels in male pain patients were not significantly different from controls. There was no difference in CSF HVA and beta-endorphins regardless of grouping; specifically we could not confirm lowered HVA concentrations in depressed patients. In general, HVA was increased though this reached only significance when comparing all female to all male pain patients. Analysis of CSF DOPAC did not provide any useful information. These data do not support the hypothesis that chronic pain patients are characterized by primary abnormalities in CSF biogenic amines - at least not in the ones examined. The striking finding of elevated CSF 5-HIAA levels is only present in female patients. Thus, it is unlikely to reflect a general vulnerability of all pain patients but is suggestive of a different reaction of females to pain. The concept that CSF 5-HIAA is elevated in response to pain is supported by elevations of similar magnitude measured in patients with acute pain [13]. The reason for a gender difference in CSF 5-HIAA response to pain is unknown. Gender differences in CSF 5-HIAA have been inconsistently reported; one study described consistently higher levels in females than in males [6], while another reported the opposite [9]. Nevertheless, the elevation of 5-HIAA only in our female pain patients was so surprising that we rechecked both CSF and statistical analyses. We arranged a subset (n = 22 patients) of CSF samples from the same aliquot to be analyzed for 5-HIAA and HVA by a different laboratory (C.C. Chiueh, Laboratory of Clinical Science, National Institute of Mental Health, Bethesda, MD). Between laboratories there was a consistent difference in the same direction in both patient samples and laboratory controls; this did not affect statistical significance. We then applied multivariant analysis of data to account for dependency on biological
197
variables. No dependency was found that could not be explained by gender. The general elevation of 5-HIAA in pain patients reported in the literature may be explained by failure to control for gender similar to the elevation seen in the first analysis of our pooled data. We conclude that there is a strong gender influence on CSF 5-HIAA in pain patients. Stated in other terms, female patients respond biochemically to pain differently than males. This finding may have therapeutic implications. Certainly, future CSF neurotransmitter studies in pain patients will have to control for gender. Our patients were matched for pain, but only a portion - though a large one showed evidence of Major Depressive Disorder. Originally it was thought that depression invariably follows chronic pain. Recent studies do not confirm such an inevitable relationship but describe an independent incidence of depression when examining chronic pain patients with standardized criteria [12,16,19]. However, this incidence is 2-4 times higher than would be expected for a general population [23]. This is also seen in our patients. Depressed pain patients were indistinguishable in CSF 5-HIAA, HVA, and beta-endorphins from their non-depressed counterparts and we did not find a correlation between endogenous opioids and the investigated neurotransmitters. However, the presence of depression abolished a positive correlation between CSF 5-HIAA and HVA which is present in non-depressed pain patients and controls. The underlying mechanism for this phenomenon is not known.
References 1 Almay, B.G.L., Johansson, E., von Knorring, L., Sakurada, T. and Terenius, L., Long-term high freouency transcutaneous electrical nerve stimulation (hi-TNS) in chronic pain. Clinical response and effects on CSF-endorphins, monoamine metabolites, substance P-like immunoreactivity (SPLI) and pain measures, J. psychosom. Res., 29 (1985) 247-257. 2 Almay, G.L., Johansson, F., von Rnorring, L., Sedvall, G. and Terenius, L., Relationship between CSF levels of endorphins and monoamine metabolites in chronic pain patients, Psychopharmacologia (Berl.), 67 (1980) 139-142. 3 Almay, B.G.L., Johansson, F., von Knorring, L., Terenius, L. and Wahlstriim, A., Endorphins in chronic pain. I. Differences in CSF endorphin levels between organic and psychogenic pain syndromes, Pain, 5 (1978) 153-162. 4 American Psychiatric Association, Diagnostic and Statistical Manual of Mental Disorders, 3rd edn, APA, Washington, DC, 1980. 5 Asberg, M., Bert&son, L., Martensson, B., Scalia-Tomba, G.P., Thoren, P. and Traskman-Bendz, L., CSF monoamine metabolites in melancholia, Acta psychiat. scand., 69 (1984) 201-219. 6 Asberg, M., Bertilsson, L., Tuck, D., Cronholm, B. and Sjtiqvist, F., Indolamine metabolites in the cerebrospinal fluid of depressed patients before and during treatment with nortriptyline, Clin. Pharmacol. Ther., 14 (1973) 277-286. 7 Basbaum, AI. and Fields, H.L., Endogenous pain control mechanism: review and hypothesis, Ann. Neurol., 4 (1978) 451-462. 8 Blumer, D. and Heilbromr, M., The pain-prone disorder: a clinical and psychological profile, Psychosomatics, 22 (1981) 395-402. 9 Coppen, A., Prange, A.J., Whybrow, P.C. and Noguera, R., Abnormalities of indolamines in affective disorders, Arch. gen. Psychiat., 26 (1972) 474-478.
198 10 Davis, G.C., Buchsbaum, MS. and Bunney, W.E., Analgesics to painful stimuli in affective illness, Amer. J. Psychiat., 136 (1979) 1148-1151. 11 France, R.D., Houpt, J.L. and Ellingwood, E.H., Therapeutic effects of antidepressants in chronic pain, Gen. Hosp. Psychiat., 6 (1984) 55-63. 12 France, R.D., Houpt, J.L.. Skott, A., Krishnan, K.R.R. and Varia, I.M., Depression as a psychopathological disorder in chronic low back pain patients, J. psychosom. Res., 30 (1986) 127-133. 13 Ghia, J.N., Mueller, R.A., Duncan, G.H., Scott, D.S. and Mao, W., Serotonergic activity in man, as a function of pain, pain mechanisms, and depression, Anesth. Analg., 60 (1981) 854-861. 14 ~a~ond, D., Ph~macoIo~ of central pan-m~uiating networks (biogenic amines and nonopioid analgesics). In: H.L. Fields et al. (Eds.), Advances in Pain Research and Therapy, Vol. 9, Raven Press, New York, 1985. 15 Hong, J.S., Yoshikawa, K. and Hendren, R.W., Measurement of beta-endorphin and enkephalins in biologica tissues and fluids, Meth. Enzymol., 103 (1983) 547-564. 16 Krishnan, K.R.R., France, R.D., Pelton, S., McCann, U.D., Davidson, J. and Urban, B.J.. Chronic pain and depression. I. Classification of depression in chronic low back pain patients, Pain, 22 (1985) 279-287. 17 Lindstrom, L.H., Widerlov, E., Geinse, L.M., Wahlstrom, A. and Terenius, L., Endorphins in human cerebrospinal fluid: clinical correlations to some psychiatric states. Acta psychiat. stand., 57 (1978) 153-164. 18 Melzack, R., The McGill Pain Questionnaire: major properties and scoring methods, Pain. 1 (1975) 277-299. 19 Pilowsky, I., Chapman, CR. and Bonica, J.J.. Pain. depression, and ilness behavior in a pain clinic population, Pain, 4 (1977) 183-192. 20 Traskman, L., Asberg, M., Bertilsson, L. and Sjostrand, L., Monoamine metabolites in CSF and suicidal behavior, Arch. gen. Psychiat., 38 (1981) 31-36. 21 Van Praag, H.M., Significance of biochemical parameters in the diagnosis, treatment and prevention of depressive disorders, Biol. Psychiat.. I2 (1977) 101-131. 22 Walsh, T.D., Antidepressants in chronic pain, Clin. Neuropharmacol., 6 (1983) 271-295. 23 Weissman, M.M. and Boyd, J.H., Epidemiology of affective disorders: a re-examination and future directions, Arch. gen. Psychiat., 38 (1981) 103991046. 24 Wilson, W.P., Blazer. D.G. and Nashold, B.S., Observation on pain and suffering Psychosomatics, 17 (1976) 73-76.
Pain, 31 (1987) 189-198 Elsevier
PA1 01107
CSF monoamine metabolites in chronic pain
Clinton
’
Randal D. France *, Bruno J. Urban * * , Susan Pelton * , D. Kilts * , Jau-Shyong Hong * * * and Charles B. Nemeroff
*
Departments of * Psychiatry and * * Anesthesiology, Duke University Medical Center, and * * * Laboratoty of Behavioral and Neurological Toxicology, National Institute ofenvironmental Health Services, Durham, NC (U.S.A.) (Received
22 January
1987, revised received and accepted
2 April 1987)
summary
Metabolites of selected neurotransmitters (5-H&A, HVA and DOPAC) and beta-endorphin were measured in the CSF of 39 chronic pain patients and compared to controls. Twelve of the pain patients also fulfilled criteria for major depression. The con~ntration of 5-HIAA was increased in female but not male pain patients; there was no significant difference in the CSF concentrations of HVA and DOPAC. The presence of depression did not influence the concentrations of nemotransmitters. No correlation was found between the concentrations of monoamine metabolites and beta-endorphin. However, there was a positive correlation between 5-HIAA and HVA in controls and chronic pain patients without depression but not in depressed patients. It is concluded: chronic pain states are associated with elevation of CSF 5-HIAA in female patients; depression abolishes a positive correlation between 5-HIAA and HVA. Key words: Neurotransmitters;
Depression;
CSF; Chronic
pain states
Intmduetion
Many chronic pain states are characterized by a pain complaint out of proportion to evidence for ongoing nociception and by affective and behavioral responses which may often progress to a psychiatric illness. Indeed, it has been proposed that clinical depression inv~ably follows chronic pain [8,24]. Both, pain and depression, are thought to be associated with alterations of endogenous opioid substances and biogenic amines in the central nervous system
’ Monoamine metabolite analysis MH-4019 and AG-05128.
was partially
supported
by NIMH
Correspondence to: Randal D. France, M.D., Assistant Medical Center, Box 3903, Durham, NC 27710, U.S.A.
03043959/87/$03.50
0 1987 Elsevier Science Publishers
Professor
Grants
MH-40542,
of Psychiatry,
B.V. (Biomedical
Division)
Duke
MH-39415,
University
190
(CNS). There is evidence that opioid-like substances excite specific neural structures which in turn produce antinociception by inhibiting transmission of noxious evoked impulses at the spinal level. A negative feedback loop of endogenous pain control has been postulated involving various neurotransmitters, most notably serotonin and norepinephrine [7]. The same endogenous opioid substances and neurotransmitters have also been reported to be altered in depression [3,17]. The elevated pain threshold in certain depressed patients has been linked to elevated concentrations of endorphins [lo]. Subtypes of depression have been associated with CNS deficiencies in serotonin and norepinephrine [21]. Studies of CNS biogenic amines in chronic pain patients are scanty and equivocal. One group reported elevated concentrations of cerebral spinal fluid (CSF) 5-hydroxyindoleacetic acid (5-H&4), a metabolite of serotonin in chronic pain patients but also in patients with acute pain [13]. There was no relationship between concentrations of 5-HIAA and pain or degree of depressive symptomatology. Another group described a wide variation in CSF 5-HIAA concentrations which were interpreted as ‘abnormal’ and ‘skewed towards lower levels’ [2]. There was no difference in CSF levels of 5-HIAA and homovanillic acid (HVA), a metabolite of dopamine, between patients with ‘organic’ pain and those with ‘psychogenic’ pain. A positive correlation was reported between CSF 5-HIAA and fraction I endorphins, an uncharacterized opioid. Neither study utilized concomitant controls. The paucity and discrepant nature of these data prompted us to investigate CSF monoamine metabolites in chronic pain patients and explore their relationship to beta-endorphin and depression.
Methods Description of patients A total of 39 patients (14 male, 25 females; mean age: 44 years, range 29968 years) with chronic low back pain/sciatica were studied. They had failed to improve with extensive medical and surgical treatments. They had undergone an average of 2.4 + 1.4 (range O-7) operations for their pain complaint. All patients experienced continuous daily pain for at least 6 months (mean 73.9, range 6-24 months). Severity of pain as measured by the mean total McGill Pain Questionnaire [18] score was 35.8 + 12.5 (range 14-73). Medical evaluation provided evidence of neurological dysfunction explaining location but not intensity of pain; there was no indication for further etiological treatment. Psychiatric evaluation by structured interview arrived at the diagnosis of Major Depressive Disorder (MDD) in 12 patients (31%). The remainder were diagnosed as No Diagnosis, Somatoform Disorder, Dysthymic Disorder or Adjustment Disorder (DSM-III criteria [4]). Since MDD has biological components which the other diagnoses lack, we felt justified in grouping these latter diagnoses together under the heading of No MDD. In no case was there evidence of Dementia, Personality and Substance Abuse Disorders, or obvious secondary gains.
191
Controls Twenty-two patients (9 male, 13 females, mean age: 25.9 years, range: years) free of chronic pain and MDD who underwent elective operation spinal anesthesia served as controls.
20-39 under
CSF sampling CSF samples were obtained after the pain patients had been free of psychoactive medications for a minimum of 1 week. With the patient in the lateral position, a spinal tap was performed at the L,_, or L,-, interspace. Sampling was performed in pain patients between 11.00 and 14.00 h, and at various times during the day in controls. Five ml of CSF were collected passively in 1 ml aliquots and immediately stored at -70°C. CSF was always clear and without evidence of contamination with blood. CSF analysis CSF concentrations of 5-H&%, HVA and DOPAC (3,4_dihydroxyphenylacetic acid), another metabolite of dopamine, were determined in the first aliquot by on-line tracer enrichment high performance liquid chromatography (HPLC) with electrochemical detection. To 500 ~1 aliquots of CSF was added 5 ~1 concentrated glacial acetic acid and 10 ng of 5-hydroxyindole-2-carboxylic acid (5-HICA, 5-HICA internal standard). Following centrifugation (10,000 X g for 5 min at 4” C) the entire sample was injected into the HPLC apparatus. The DOPAC, HVA, 5-HIAA and 5-HICA were on-line enriched on short octadecyl bonded HPLC enrichment columns (4 (I.D.) x 30 mm, Alltech Ass., Dearfield, IL) and subsequently separated by anion exchange HPLC (4 X 250 mm, SAX on 5 pm microparticulate silica, Chromanetics, Kensington, MD). The enrichment mobile consisted of 0.075 M KH PO (pH 3.0) and the analytical mobile phase consisted of 0.075 M KH PO (pH 4.5) with 5% acetonitrile. Both mobile phases were degassed by vacuum filtration and ultrasonic agitation prior to their isocratic delivery at 1.25 ml/mm. DOPAC, HVA, 5-HIAA and 5-HICA were detected amperometrically following electrochemical oxidation at a glassy carbon working electrode potential of +750 mV vs. an Ag/AgCl reference electrode (Bioanalytical Systems, Inc., Lafayette, IN). Calibration curves were generated by assaying 500 ~1 volumes of artificial CSF to which varying amounts (0, 2-40 ng) of DOPAC, HVA and 5-HIAA and a fixed amount (10 ng) of 5-HICA were added. The concentrations of DOPAC, HVA and 5-HIAA in human CSF samples were calculated from their peak height ratio relative to 5-HICA, using the slope and intercept of the appropriate calibration curve. Samples from pain patients and controls were analyzed concomitantly. In 21 patients, CSF was also analyzed for beta-endorphin using a radioimmunoassay described in detail elsewhere [15]. Prior to RIA, proteins were separated by a microbandpak CA,, column. The method has a 100% cross-reactivity with beta-lipotropin, less than 0.01% with enkephalins and is without a detectable cross-reactivity with dynorphin. The absolute sensitivity of the assay is 1 pg per tube; the interassay reliability is less than 5%.
192
Data analysis Statistical analyses were performed with non-parametric and parametric tests (~uskal-Wallis and ANOVA, corrected alpha level using Bonferroni correction followed by post hoc test using Tukey). Correlations were analyzed by Spearman’s rank correlation test. Beta-endorphin data were only used for correlational analysis and intergroup comparison since simultaneous control data were not available. We applied multivariant analysis (MANOVA) when looking at the influence of gender and depression (MDD, No MDD).
Results
Patients and control groups were not significantly different in regard to gender, height and weight. There was a significant difference (P = 0.0001) between the mean ages of patients (44.2 + 10.6 years) and controls (26.9 * 5.3 years). There was no significant correlation between monoamine metabolites and age, height, and weight in patients or in controls. This held true when controlling for gender in both groups and for MDD and gender in the patient group. 5-HIAA was significantly higher in pain patients than in controls regardless of presence or absence of MDD. There was no significant difference in CSF levels of HVA and DOPAC between patients and controls (Table I). There was a large spread in values for DOPAC, with the majority of determinations (19 for controls and 26 for patients) approaching or falling below the analytic sensitivity of the method. For this reason, we decided to forego further statistical analysis of the DOPAC results. Influence of gender and clepression When analyzing the pain and control groups separately, 5-HIAA was significantly higher in all female pain patients when compared with male pain patients (Table II). There was no gender difference in the control groups (Table II). HVA levels were generally evaluated in females. This elevation was only significant when comparing female pain patients with male pain patients (Table III). Again, there was no gender difference in the control groups.
TABLE
i
CSF MONOAMINE
METABOLITES
All pain patients
IN CHRONIC
PAIN
22.6+
HVA DOPAC
40.1+ 18.89 1.4+ 2.49
8.46
PATIENTS P
Groups
5-HIAA
* P -z 0.05 (Tukey).
@g/m{)
1. Pain with MDD
2. Pain with no MDD
23.0+
22.Si
7.54
43.4 * 15.40 1.21 1.84
8.97
38.7 i 20.35 1.5+ 2.76
3. Controls l&3*
5.05
32.0 i 10.55 0.6i 1.44
0.01 NS NS
ANR
CONTROLS
Group
comparisons
l-2
2--3
1-3
*
*
193 TABLE
II
5-HIAA (q/ml): ANALYSIS AGNOSTIC GROUPS
OF
VARIANCE
Male (jzk S.D.) 17.2+5.07 n=14 17.4 f 2.55 n=3 17.2 f 5.67 n=ll 15.3*5.74 n=9
Total pain patients Pain with MDD Pain no MDD Controls
TABLE
ANALYSIS
Total pain patients Pain with MDD Pain no MDD Controls
CONTROLLING
FOR
Female (X+S.D.)
KruskalWaIIis (P)
ANOVA
25.6 + 8.54 n = 25 24.8 f 7.82 n=9 26.1 f 8.13 n=16 17.0 f 4.6 n=13
0.002
0.0018
NS
NS
0.008
0.008
NS
NS
DI-
(P)
OF VARIANCE
ACROSS
GENDER
CONTROLLING
FOR
DIAGNOS-
Male (X f SD.)
Female (X+S.D.)
KruskaIWallis (P)
ANOVA
31.7 n=l4 36.6 n=3 30.3 n=ll 29.9 n=9
f 13.75
44.9 + 19.32 n = 25
0.03
0.034
f 19.02
45.7 f 14.59 n=9
NS
NS
f 12.80
44.47 f 27.83 n=16 33.7+ 9.42 n=13
NS
NS
NS
NS
f 12.1
(P)
IV
5-HIAA (ng/ml): FOR GENDER
ANALYSIS
OF VARIANCE
ACROSS
Pain patients 1. MDD (X f S.D.)
2. No MDD (X f S.D.)
3. Controls (X+ S.D.)
Total pain patients
23.0 f 7.54 n=12
22.5 f 8.97 n = 27
Male
17.4*2.55 n=3 24.8 + 7.82
17.2 + 5.67 n=ll 26.lk9.13
16.3 n = 15.3 n=9 17.0
n=9
n=16
n=13
Female
GENDER
III
HVA (ng/ml): TIC GROUPS
TABLE
ACROSS
* P < 0.05 (Tukey).
DIAGNOSTIC
GROUPS
KruskalWallis (P)
ANOVA
(P)
f 5.05 22 + 5.74
-
0.01
NS
NS
f 4.62
0.006
0.007
CONTROLLING
Group
comparisons
l-2
2-3
1-3
*
*
*
194
VVIH-9
VVIH-S
VVIH-S
VVIH-S
195
When comparing across gender and controlling for diagnostic groups (MDD, No MDD), 5-HIAA remained significantly elevated in female pain patients without MDD when compared to male pain patients without MDD (Table II). A similar comparison between male and female pain patients with MDD showed a difference of similar magnitude that was not statistically significant. There was no interaction between diagnostic groups and gender. In contrast, the earlier differences found in HVA levels between male and female pain patients were no longer significant when controlling for diagnostic groups and comparing across gender. We further investigated the influence of MDD on 5-HIAA by comparing pain patients with and without MDD to controls of the same sex (Table IV). S-HIAA in male patients with MDD was not significantly different from male patients without MDD or from male controls. In female pain patients, 5-HIAA was significantly elevated in patients without MDD compared to female controls. In female patients with MDD, a similar elevation of 5-HIAA was not significant. Correlations Correlational analysis demonstrated a significant positive relationship between 5-HIAA and HVA (r = 0.62, P = 0.002) for the control group (Fig. 1). When controlling for gender, this relationship failed to reach significance in female controls although the slopes were similar. All pain patients combined showed a strong positive correlation between 5-H&4 and HVA (r = 0.55, P = 0.0003). When controlling for gender and MDD, this correlation was only seen in chronic pain patients, male or female, without MDD. In depressed patients, this relationship did not hold (Fig. 1). Beta-endorphin did not correlate with 5-HIAA and HVA in pain patients. This also held true when controlling for gender or MDD. There was no difference in beta-endorphin between patients with and without MDD. Likewise, there was no gender difference in pain patients without MDD; the number of patients with MDD was too small for meaningful gender comparison.
Discussion Neurotransmitters have been located throughout the neuraxis; beta-endorphins and dopamine more in supraspinal levels while serotonin had been found in spinal locations as well. Chemical analysis of CSF for these substances is thought to reflect CNS changes [14]; alterations have been described in pain patients and depressives. The mechanism for interaction of neurotransmitters and reason for change are unknown. Nevertheless, neurochemical analysis may be used to correlate with treatment effect [l]. Alterations of CNS neurotransmitters in chronic pain patients may be an independent phenomenon or they may occur as a reaction to pain. Changes in CSF biogenic amines have previously been reported to occur in deviant behaviors. Abnormally low concentrations of 5-HIAA were observed in depressed and non-depressed patients who had attempted violent suicides; concentrations of HVA were
196
also lowered but only in the depressed patients [20]. These data were interpreted as reflecting a possibly genetically increased vulnerability to a range of psychiatric disturbances and to suicidal behavior. In a similar manner it is conceivable that a chronic pain state is more likely to occur in patients who are biologically susceptible. This hypothesis would explain the occurrence of a chronic pain syndrome in a subgroup of patients while other patients with a similar medical condition undergo uneventful recovery. It would further explain the high incidence of major depression in chronic pain patients and the positive response of both conditions to antidepressants [11,22]. From the literature, CNS biogenic amines seem the most likely substances to reflect abnormalities associated with pain and depression. In this study, we tried to minimize the effects of other variables on CSF biogenic amines. All patients were free of psychoactive medications. To control for diurnal variation and for a gradient of CSF metabolites within the spinal fluid column, we performed spinal taps at the same time of day, at the same interspace, and with the patient in the same position. We found no correlation between monoamine metabolites and weight, age, or height in pain patients and controls: these latter two findings are in contrast to the literature [5]. We did find that chronic pain patients show a general elevation in concentrations of CSF 5-HIAA regardless of the presence or absence of major depression. This confirms previous observations [13]. However, when analyzing our data across gender we found elevated levels of CSF 5-HIAA only in female patients. CSF 5-HIAA levels in male pain patients were not significantly different from controls. There was no difference in CSF HVA and beta-endorphins regardless of grouping; specifically we could not confirm lowered HVA concentrations in depressed patients. In general, HVA was increased though this reached only significance when comparing all female to all male pain patients. Analysis of CSF DOPAC did not provide any useful information. These data do not support the hypothesis that chronic pain patients are characterized by primary abnormalities in CSF biogenic amines - at least not in the ones examined. The striking finding of elevated CSF 5-HIAA levels is only present in female patients. Thus, it is unlikely to reflect a general vulnerability of all pain patients but is suggestive of a different reaction of females to pain. The concept that CSF 5-HIAA is elevated in response to pain is supported by elevations of similar magnitude measured in patients with acute pain [13]. The reason for a gender difference in CSF 5-HIAA response to pain is unknown. Gender differences in CSF 5-HIAA have been inconsistently reported; one study described consistently higher levels in females than in males [6], while another reported the opposite [9]. Nevertheless, the elevation of 5-HIAA only in our female pain patients was so surprising that we rechecked both CSF and statistical analyses. We arranged a subset (n = 22 patients) of CSF samples from the same aliquot to be analyzed for 5-HIAA and HVA by a different laboratory (C.C. Chiueh, Laboratory of Clinical Science, National Institute of Mental Health, Bethesda, MD). Between laboratories there was a consistent difference in the same direction in both patient samples and laboratory controls; this did not affect statistical significance. We then applied multivariant analysis of data to account for dependency on biological
197
variables. No dependency was found that could not be explained by gender. The general elevation of 5-HIAA in pain patients reported in the literature may be explained by failure to control for gender similar to the elevation seen in the first analysis of our pooled data. We conclude that there is a strong gender influence on CSF 5-HIAA in pain patients. Stated in other terms, female patients respond biochemically to pain differently than males. This finding may have therapeutic implications. Certainly, future CSF neurotransmitter studies in pain patients will have to control for gender. Our patients were matched for pain, but only a portion - though a large one showed evidence of Major Depressive Disorder. Originally it was thought that depression invariably follows chronic pain. Recent studies do not confirm such an inevitable relationship but describe an independent incidence of depression when examining chronic pain patients with standardized criteria [12,16,19]. However, this incidence is 2-4 times higher than would be expected for a general population [23]. This is also seen in our patients. Depressed pain patients were indistinguishable in CSF 5-HIAA, HVA, and beta-endorphins from their non-depressed counterparts and we did not find a correlation between endogenous opioids and the investigated neurotransmitters. However, the presence of depression abolished a positive correlation between CSF 5-HIAA and HVA which is present in non-depressed pain patients and controls. The underlying mechanism for this phenomenon is not known.
References 1 Almay, B.G.L., Johansson, E., von Knorring, L., Sakurada, T. and Terenius, L., Long-term high freouency transcutaneous electrical nerve stimulation (hi-TNS) in chronic pain. Clinical response and effects on CSF-endorphins, monoamine metabolites, substance P-like immunoreactivity (SPLI) and pain measures, J. psychosom. Res., 29 (1985) 247-257. 2 Almay, G.L., Johansson, F., von Rnorring, L., Sedvall, G. and Terenius, L., Relationship between CSF levels of endorphins and monoamine metabolites in chronic pain patients, Psychopharmacologia (Berl.), 67 (1980) 139-142. 3 Almay, B.G.L., Johansson, F., von Knorring, L., Terenius, L. and Wahlstriim, A., Endorphins in chronic pain. I. Differences in CSF endorphin levels between organic and psychogenic pain syndromes, Pain, 5 (1978) 153-162. 4 American Psychiatric Association, Diagnostic and Statistical Manual of Mental Disorders, 3rd edn, APA, Washington, DC, 1980. 5 Asberg, M., Bert&son, L., Martensson, B., Scalia-Tomba, G.P., Thoren, P. and Traskman-Bendz, L., CSF monoamine metabolites in melancholia, Acta psychiat. scand., 69 (1984) 201-219. 6 Asberg, M., Bertilsson, L., Tuck, D., Cronholm, B. and Sjtiqvist, F., Indolamine metabolites in the cerebrospinal fluid of depressed patients before and during treatment with nortriptyline, Clin. Pharmacol. Ther., 14 (1973) 277-286. 7 Basbaum, AI. and Fields, H.L., Endogenous pain control mechanism: review and hypothesis, Ann. Neurol., 4 (1978) 451-462. 8 Blumer, D. and Heilbromr, M., The pain-prone disorder: a clinical and psychological profile, Psychosomatics, 22 (1981) 395-402. 9 Coppen, A., Prange, A.J., Whybrow, P.C. and Noguera, R., Abnormalities of indolamines in affective disorders, Arch. gen. Psychiat., 26 (1972) 474-478.
198 10 Davis, G.C., Buchsbaum, MS. and Bunney, W.E., Analgesics to painful stimuli in affective illness, Amer. J. Psychiat., 136 (1979) 1148-1151. 11 France, R.D., Houpt, J.L. and Ellingwood, E.H., Therapeutic effects of antidepressants in chronic pain, Gen. Hosp. Psychiat., 6 (1984) 55-63. 12 France, R.D., Houpt, J.L.. Skott, A., Krishnan, K.R.R. and Varia, I.M., Depression as a psychopathological disorder in chronic low back pain patients, J. psychosom. Res., 30 (1986) 127-133. 13 Ghia, J.N., Mueller, R.A., Duncan, G.H., Scott, D.S. and Mao, W., Serotonergic activity in man, as a function of pain, pain mechanisms, and depression, Anesth. Analg., 60 (1981) 854-861. 14 ~a~ond, D., Ph~macoIo~ of central pan-m~uiating networks (biogenic amines and nonopioid analgesics). In: H.L. Fields et al. (Eds.), Advances in Pain Research and Therapy, Vol. 9, Raven Press, New York, 1985. 15 Hong, J.S., Yoshikawa, K. and Hendren, R.W., Measurement of beta-endorphin and enkephalins in biologica tissues and fluids, Meth. Enzymol., 103 (1983) 547-564. 16 Krishnan, K.R.R., France, R.D., Pelton, S., McCann, U.D., Davidson, J. and Urban, B.J.. Chronic pain and depression. I. Classification of depression in chronic low back pain patients, Pain, 22 (1985) 279-287. 17 Lindstrom, L.H., Widerlov, E., Geinse, L.M., Wahlstrom, A. and Terenius, L., Endorphins in human cerebrospinal fluid: clinical correlations to some psychiatric states. Acta psychiat. stand., 57 (1978) 153-164. 18 Melzack, R., The McGill Pain Questionnaire: major properties and scoring methods, Pain. 1 (1975) 277-299. 19 Pilowsky, I., Chapman, CR. and Bonica, J.J.. Pain. depression, and ilness behavior in a pain clinic population, Pain, 4 (1977) 183-192. 20 Traskman, L., Asberg, M., Bertilsson, L. and Sjostrand, L., Monoamine metabolites in CSF and suicidal behavior, Arch. gen. Psychiat., 38 (1981) 31-36. 21 Van Praag, H.M., Significance of biochemical parameters in the diagnosis, treatment and prevention of depressive disorders, Biol. Psychiat.. I2 (1977) 101-131. 22 Walsh, T.D., Antidepressants in chronic pain, Clin. Neuropharmacol., 6 (1983) 271-295. 23 Weissman, M.M. and Boyd, J.H., Epidemiology of affective disorders: a re-examination and future directions, Arch. gen. Psychiat., 38 (1981) 103991046. 24 Wilson, W.P., Blazer. D.G. and Nashold, B.S., Observation on pain and suffering Psychosomatics, 17 (1976) 73-76.