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Hormonal effects of high dose naloxone in humans
Neuropeptides 6: 373-380, 1985
HORMONAL EFFECTS OF HIGH DOSE NALOXONE IN HUMANS
Martin R4 Cohen', Robert M.4Cohen2, David Pickar3, Don Kreger3, Cathy McLellan , Dennis L. Murphy 1 The Ensor Foundation Research Lab, The William S. Hall Psychiatric Institute, and the Department of Neuropsychiatry and Behavioral Science, Schoo120f Medicine, University of South Carolina, P.O. Box 202, Columbia, SC, 29202 Section on Clinical Bsain Imaging, Lab of Psychology & Psychopathology, NIMH, Bethesda, MD., Section tn Clinical Studies, Clinical Neuroscience Branch, NIMH, Bethesda, MD., Clinical Neuropharmacology Branch, NIMH, Bethesda, MD. /Reprint requests to MC/
ABSTRACT Utilizing a double-blind crossover design, the hormonal effects of high dose, 2 mg/kg, were compared to low dose, 0.4 mg (approx. 5 ug/kg), naloxone administration in physically healthy humans. A significant naloxone dose effect on plasma cortisol levels was found (pUl.OOl), but no significant effect on plasma or serum levels of prolactin, follicle stimulating hormone, luteinizing hormone, norepinephrine or epinephrine. These results confirm involvement of the endogenous opioid system (EOS) in the tonic regulation of the hypothalamicpituitary-adrenalaxis, but fail to find evidence of EOS involvement in the regulation of adrenal medullary function or the gonadotrophic axis in man. The results are however consistent with a continuing action of naloxone as an EOS antagonist even at high doses in man.
INTRODUCTION The discovery of the endogenous opioid system (EOS) has led to an intensive investigation of its potential importance in human physiology (I-11). Alterations in physiologic parameters following the administration of opioids in humans support this potential (12-17). However, effects following the administration of naloxone, a drug which is assumed to block the functioning of the EOS would provide more direct evidence of the system's current functioning and importance (18). We have noted in greater detail elsewhere that many clinical studies with naloxone may have used an insufficient dose to assure functional blockade of all relevant EOS's (18). In a study utilizing a single-blind design, we reported blood pressure and behavioral effects of naloxone, when administered in the mg/kg range to humans, that were not evident in previous studies using lower doses of naloxone (18,19). With the exception of our preliminary 373
single-blind study, previous studies of hormonal effects of naloxone administration in humans have used low dcses (less than or equal to 0.5 mg/kg) (2, In this study, we evaluate the hormonal consequences of a high 7,16,20,21). dose (2mg/kg) compared to a low dose (approximately 5 ug/kg) of naloxone using a double-blind crossover design. METHODS Hormonal effects were evaluated in eight women and six men (n=14) aged 19 to 56 years, free of systemic physical illness. All gave informed consent prior to their participation; all were free of drugs for at least 3 days prior to their study and free from opiates for at least the 3 preceeding Seven of the volunteers at the time of the study were suffering from weeks. mental disorders, three from major depression and four from schizophrenia (DSM III criteria). Patients who had been on a chronic medication regime had been withdrawn from all drugs at least 2 weeks prior to their study. By exclusion, no subject had a history of drug or alcohol abuse. The study utilized a double-blind, random but balanced crossover design so that each volunteer or patient was administered 2 mg/kg or 0.4 mg. (approximately 5 ugfkg) of naloxone intravenously (iv) on separate days at least 72 hours apart. Each day began at 0830 hours following an overnight A catheter was placed in an arm vein and kept patent with heparin. At fast. 0920, 0.4 mg. naloxone (a test dose) was administered iv to eliminate the possibility of undetected or recent opiate intake by a volunteer. This use could have led to a severe withdrawal reaction following the administration of a high dose of naloxone as well as complicate any conclusions regarding the effect of a high dose of naloxone on the EOS. The 0.4 mg. naloxone should not have added significantly to the following 2 mg/kg dose. Only after this low dose of naloxone failed to produce effects of opiate withdrawal (as was always the case) was an iv infusion (double-blind dose) of 2 mg/kg naloxone dissolved in less than 20 cc normal saline vehicle or a normal saline vehicle of equal volume (placebo) administered over less than 2 Thus, although a placebo was used to blind the minutes at 0930 hours. there was no day during which the administration of high dose naloxone, subject received placebo alone. Subjects were required to lie in a supine position for a brief period of time prior to and following their infusions (from 0915 until 1000 hours) and for 5 minutes prior to the withdrawal of each blood sample. Subjects were not permitted to eat during the testing period; otherwise, activity that was not physically strenuous was permitted. Blood samples were obtained for hormonal evaluations immediately prior and at 0.5, 1 and 2 hours to the 0.4 mg naloxone test infusion (0, baseline) Samples were immediately split for the following the double-blind infusion. Blood for plasma preparation was separate preparation of plasma and serum. placed on ice; within 30 minutes plasma was obtained by centrifugation for 15 minutes at 3,000 rpms (O-4’ C) and aliquots were frozen at (-80” C) for Serum was obtained by allowing the blood to clot at room future assay. subsequent handling was the same as for the plasma preparation. temperature-; Hormone determinations were conducted using commercially supplied reagents were obtained from New England Nuclear; For cortisol, agents. 374
refor
prolactin, follicle stimulating hormone (FSH), and luteinizing hormone (LH) reagents were obtained from Immuno Nuclear. The hormone responses of an individual on both days of the study were always determined within the same assay. Intra-assay coefficients of variation was 6% or less; inter-assay variation was less than 10%. Plasma epinephrine and norepinephrine were measured by high-pressure liquid chromatography with electrochemical detection (22). Statistical analysis of the effect of naloxone dose on plasma or serum hormone levels was accomplished using repeated measures analysis of variance (anovar). The degrees of freedom sometimes varied with the analysis of a given hormone because technical limitations sometimes decreased the study There was no correlation of hormone sample size from N=14 (but always N>9). responses with age, sex or psychiatric diagnosis. However, in the evaluation of the naloxone dose effect on serum prolactin levels, the study sample excluded patients with depression. Previous reports have suggested an abnormal lack of responsiveness of serum prolactin levels to opioid agonists in depression (23,24). Prolactin measurements were accomplished at baseline, 0.5 and 1 hour post infusion since our previous single blind study had suggested that a naloxone dose effect on prolactin would be most likely to occur within this first hour (18). RESULTS The mean + SEM of the measured plasma and serum hormone levels are presented in Table I. Only plasma cortisol levels were found to be significantly affected by naloxone dose. Evaluation of individual cortisol responses established the consistency of the response. Thirteen of fourteen subjects showed a greater maximum change in plasma cortisol levels during the high compared to the low dose naloxone day. In the case of the gonadotrophic hormones, we evaluated the possibility that there might be differences in the hormonal responses of men and women that might obscure a naloxone dose effect but found no significant effect of sex on either the FSH or LH response. DISCUSSION An increase in plasma cortisol levels following high dose naloxone administration is consistent with results from previous human studies of the effects of low doses of naloxone (6,8,21,25) as well as with reports of plasma cortisol suppression following opioid agonist administration (25-28). The data is entirely consistent with the hypothesis that the EOS is actively involved in the tonic regulation of plasma cortisol levels in humans. In contrast to cortisol, serum prolactin was found not to be significantly affected by naloxone dose. This result is consistent with our previous singleblind study of high dose naloxone administration as well as with previous low dose studies in humans which in the great majority have found no alteration of prolactin levels with naloxone administration (6,9, 29). These results are not consistent with EOS involvement in the tonic regulation of serum prolactin levels. Nevertheless, the potential for EOS involvement in the regulation of prolactin secretion under special circumstances is suggested by the increase in serum prolactin levels that is found
375
during human adaptation to stress (30) and following opioid agonist administration in humans (23,24,28).
TABLE I Effect of Naloxone Dose on Serum or Plasma Hormone Concentrations (MeanfSEM)
Hormone (units)
0.4 mg (approx.Sug/kg)
0
2 mg/kg Dose
(Hrs. post-infusion) 0.5 1 2
0
No.of Subjects
Significance
(Hrs. post-infusion) 0.5 1 2
Cortisol (ugX)
11.9 21.1
10.0 21.1
10.3 9.8 +1.5 21.3
12.6 +1.1
18.8 19.4 16.9 21.5 +1.2 +1.8
PRL (r&ml)
12.2 +3.0
10.3 22.1
8.7 t1.6
12.5 +3.0
14.7 24.7
13.3 23.7
LH (mIu/ml)
2.1 20.7
1.6 20.7
3.1 2.4 20.6 to.7
2.0 20.5
2.5 to.6
FSH (mIu/ml)
2.9 to.7
3.4 to.7
3.7 3.7 20.8 20.7
4.0 20.7
3.2 to.8
Epinephrine (pglml)
182 ?56
124 237
145 +46
141 +43
114 226
163 241
149 f42
Norepinephrine(pg/ml)
219 +27
201 +29
213 +35
255 ?45
161 214
140 ?18
168 221
14
&O.OOl*
9
NS+
3.9 3.0 20.7 to.5
14
NS+
4.0 3.2 fl.1 to.9
14
NS
109 ?32
10
NS
157 +18
10
NS
* Significant main effect for dose,F=l9.7 (df=1,13); significant interaction effect for dose x hour, F=ll.S (df=3,39) + NS3p70.1 for main or interaction effects
The results of animal studies have suggested the possible importance of the EOS in the regulation of gonadotrophic hormone secretion in humans (31, 32). In clinical studies opioid agonists have been demonstrated to acutely depress serum gonadotrophic levels (31). However, in this study we have not been able to find evidence to suggest EOS involvement in the regulation of either tonic FSH or LH secretion. In addition, we found no evidence of an effect of sex on the gonadotrophic hormone response to naloxone to explain the previously reported finding of increased serum LH levels in men following naltrexone administration (33). The difference in results may perhaps be attributed to an agonist effect of naltrexone at an opiate receptor subtype or to the more frequent (20x) and longer duration (8 hours) of the blood sampling for this episodically secreted hormone in the latter study. Cur findings suggest that future studies might require a more intensive and perhaps prolonged evaluation of gonadotrophin levels and/or be directed to
376
understanding the possible involvement of the EOS in episodic alterations of gonadotrophic secretion, as for example those that occur during temporal periods of the menstrual cycle or during menarche or menopause. This suggestion is consistent with previous findings that naloxone administration over a 6 hour period produced in young women an increase in episodic LH secretion during the midluteul phase (days 18-21) of the menstrual cycle but had no effect on secretion in the follicular phase or in post menopausal women (34,35). EOS involvement in adrenal medullary function has been suggested in In addition, a recent case report has suggested that animal studies (36). low dose naloxone administration may increase plasma epinephrine and norepinephrine levels in patients suffering from pheochromocytoma (37). We have previously reported an increase in systolic blood pressure in humans following the administration of increasing doses of naloxone in the mg/kg range In this study, however, we were unable to find any evidence to support (19). EOS involvement in the tonic regulation of human plasma norepinephrine or epinephrine levels. In summary, our results confirm an important role for the EOS in the tonic regulation of plasma cortisol levels in humans, but suggest a lack of involvement of the EOS in the tonic regulation of plasma or serum levels of prolactin, FSH, LH, norepinephrine or epinephrine levels in humans. However, although relatively high doses of naloxone were used in this study, higher doses or more prolonged naloxone administration may yet be required to ensure sufficient functional blockade to rule out EOS involvement in the tonic regulation of these hormone levels. The dose chosen for this study was the maximum, however, we felt could be acutely administered with a minimal of somatic complaints that might indirectly effect hormone function and/or break the blind design. The findings of this study support the conclusion that naloxone administration even at high doses in humans is without agonist activity, since the expected effects of an opioid agonist i.e. suppression of serum FSH and LH levels and an increase in serum prolactin levels were not observed. Thus, understanding of EOS involvement in episodic hormone alterations such as during human stress responses may be clarified by using a range of doses of naloxone to include doses in the mg/kg range to assure functional blockade of all relevant EOSs. REFERENCES 1.
D. and Dubois, M. (1983). The role of the Cohen, M.R., Pickar, endogenous opioid system in the human stress response. Psychiatric Clinics of North America 6: 457-471.
2.
N. and Blichert-Toft, M. (1981). Engquist, A., Hicquet, J., Saurbrey, and hemodynamic response to surgery after naloxone Cortisol, glucose, Acta Anaesthesiologica Scandinavica 25: 17-20. administration.
3.
Grevert, P. and Goldstein, A. (1978). experimental pain or mood in humans.
4.
Jones,
R. and Herning,
R.
(1979).
Naloxone fails to alter Science 199: 1093-1095,
Naloxone
377
induced
mood and physiologic
changes in normal volunteers In: Usdin, E., Bunney, W.E. and Kline, N. (eds.) Endorphins in Mental Health Research. Oxford University Press, New York, p. 484-491. 5.
Judd, L., Janowsky, D., Segal, D. and Huey, L.Y. (1980). Naloxoneinduced behavioral and physiological effects in normals and manic subjects. Archives of General Psychiatry 37: 583-586.
6.
Naber, D., Pickar, D., Davis, G., Cohen, R.M., Jimerson, D.C. Elchisak, M.A., Defraites, E.G., Kalin, N.H., Risch, S.C. and Buchsbaum, M.S. (1981). Naloxone effects on beta-endorphin, cortisol, prolactin, growth hormone, HVA & MHPG in plasma of normal volunteers. Psychopharmacology 74: 125-128.
7.
Spiler, I. and Molitch, M. (1980). Lack of modulation of pituitary hormone stress response by neutral pathways involving opiate receptors. Journal of Clinical Endocrinology and Metabalism 50: 516-520.
8.
Volavka, J., James, B., Reker, D., Pollock V. and Cho, D. (1979). Electroencepholographic and other effects of naloxone in normal men. Life Sciences 25: 1267-1272.
9.
Volavka, J., Bauman, J., Pevnick, J., Reker, D., James, B. and Cho., D. (1980). Short-term effects of naloxone in man. Psychoneuroendrocrinology 5: 225-234.
10. Wilier, J.C., Boureau, F., Dauthier C. and Bonora, M. (1979). Study of naloxone in normal awake man: effects on heart rate and respiration. Neuropharmacology 18: 469-572. 11. Zilm, D.H. (1980). Naloxone response in non-dependent man: effect on six physiological variables. Neuropharmacology 19: 591-595. 12. Brandt, M.R., Korshin, J., Hensen, A.P., Hummer, L. and Madsen, S.N. (1978). Influence of morphine anaesthesia on the endocrine-metabolic response to open-heart surgery. Acta Anesthesiologica Scandinavica 2: 400-412. 13.
Dubois, M., Pickar, D., Cohen, M.R., Gadde, P., Macnamara, T.E. and Bunney, W.E. (1982). Effects of fentanyl on the response of plasma beta-endorphin immunoreactivity to surgery. Anesthesiology 57: 468-472.
14.
Foley, K.M., Kourides, I.A., Inturrisi, C.E., Kaiko, R.F., Zaroulis, C.G., Posner, J.B., Houde, R.W. and Li, C.H. (1979). Beta-endorphin: Analgesic and hormonal effects in humans. Proceedings of the National Academy of Sciences of the USA 76: 5377-5381.
15. Jaffe, J. and Martin, W. (1975). Narcotic analgesics and antagonists. In: Goodman, L. and Gilman, A. (eds.) The Pharmacological Basis of Therapeutics. Macmillan, New York, p. 245-283. 16. Martin, W. and Jasinski, D. (1969). Physiological parameters of morphine dependence in man-tolerence, early abstinence protractual abstinence. Journal of Psychiatry Research 7: 9-17.
378
17. Tolis, G., Hickey, J. and Guyda, H. (1975). Effects of morphine on serum growth hormone, cortisol, prolactin and thyroid stimulating hormone in man. Journal of Clinical Endocrinology Metabolism 41: 797-800. 18. Cohen, M.R., Cohen, R.M., Pickar, D., Weingartner, H. and Murphy, D.L. (1983). High dose naloxone infusions in normals: dose-dependent behavioral, hormonal and physiological responses. Archives of General Psychiatry 40: 613-619. 19. Cohen, M.R., Cohen, R.M., Pickar, D., Murphy, D. and Bunney, W. (1982). Physiological effects of high dose naloxone administration to normal adults. Life Sciences 30: 2025-2031. 20.
Janowsky D., Judd, L., Huey, L., Roitman, N., Parker, D. and Segal, D. (1978). Naloxone effects on manic symptoms and growth hormone levels. Lancer 2: 320.
21. Morley, J.E., Baranetsky, N.G., Wingert, T.D., Carlson, H., Hershman, S. Melmed, S., Levin, S., Jamison, K. and Weitzman, R. (1980). Endocrine effects of naloxone-induced opiate receptor blockade. Journal of Clinical Endocrinol Metabolism 50: 251-257. 22.
Chiueh, C., Zukowska-Grojec, K., Kirk, K.L. and Kopin, I.J. (1983). 6-Fluorocatecholamines as false adrenergic neurotransmiters. Journal Pharmacology and Experimental Therapeutics 225: 529-33.
23.
Extein, I., Pottash, A., Gold, M., Sweeney, D., Martin, D. and Goodwin, F. (1980). Deficient prolactin response to morphine in depressed patients. American Journal of Psychiatry 137: 845-846.
24.
Judd, L., Risch, S., Parker, D., Janowsky, D., Segal, D. and Huey, L. (1982). Blunted prolactin response. A neuroendocrine abnormality manifested by depressed patients. Archives of General Psychiatry 39: 1413-1416.
25.
Judd, L. and Janowsky, D.S. (1981). Effects of narcotics and narcotic antagonists on affective disorders, schizophrenia and serum neurohormones. Modern Problems of Pharmacopsychiatry 17: 213-225.
26.
Gold, P., Extein, I,, Pickar, D., Ross, R. and Goodwin, F. (1980). Suppression of plasma cortisol in depressed patients by acute intravenous methadone infusion. American Journal of Psychiatry 137: 862-863.
27.
Judd, L., Parker, D., Janowsky, D., Segal, D., Risen, S. and Huey., L. (1982). The effect of methadone on the behavioral and neuroendocrine responses of manic patients. Psychiatry Research 7: 163-70.
28.
Pickar, D., Davis, G.C., Schulz, C.S., Extein, I., Wagner, R., Naber, D. Gold, P.W., van Kammen, D.P., Goodwin, F.K., Wyatt, R.J., Li, C.H. and Bunney, W.E. (1981). Behavioral and biological effects of acute betaendorphin injection in schizophrenic and depressed subjects. American Journal of Psychiatry 138: 160-166.
379
29.
Janowsky, D., Judd, L., Huey, L., Roitman, N. and Parker, D. (1979). Naloxone effects on serum growth hormone and prolactin in man. Psychopharmacology 65: 95-97.
30.
Boyd, A. and Reichlin, S. (1977). Neural Control of prolactin secretion in man. Psychoneuroendrocrinology 3: 113-130.
31.
Cicero, T. (1980). Effects of exogenous and endogenous opiates on the hypothamalic-pituitary-gonadalaxis in the male. Federation Proceedings 39: 2551-2554.
32.
Van Vugt, D. and Meites., J. (1980). Influence of endogenous opiates on anterior pituitary function. Federation Proceedings 39: 2533-2538.
33. Mendelson, J., Ellingboe, J., Keuhnle J. and Mello, N. (1979). Effects of naltrexone on mood and neuroendocrine function in normal adult males. Psychoneuroendocrinology 3: 231-236. 34.
Reid, E.L., Quigley, M.E. and Yen, S.S. (1983). The disappearance of opioidergic regulation of gonadotropin secretion in postmenopausal women. Journal of Clinical Endocrinology and Metabolism 57: 1107-1110.
35.
Ropert, J.F., Quigley, M.E. and Yen, S.S. (1981). Endogenous opiates modulate pulsatile luteninizing hormone release in humans. Journal of Clinical Endocrinology and Metabolism 52: 583-585.
36.
Amir, S., Brown, 2. and Amit, 2. (1979). The role of endorphins in stress: evidence and speculations. Neuroscience and Biobehavioral Reviews 4: 77-86.
37. Mannelli, M., Maggi, M., Defeo, M.L., Cuomo, S., Forti, G., Moroni, F. and Giusti, G. (1983). Naloxone administration releases catecholamines. New England Journal of Medicine 308: 654-655.
Accepted 7/6/85
380
HORMONAL EFFECTS OF HIGH DOSE NALOXONE IN HUMANS
Martin R4 Cohen', Robert M.4Cohen2, David Pickar3, Don Kreger3, Cathy McLellan , Dennis L. Murphy 1 The Ensor Foundation Research Lab, The William S. Hall Psychiatric Institute, and the Department of Neuropsychiatry and Behavioral Science, Schoo120f Medicine, University of South Carolina, P.O. Box 202, Columbia, SC, 29202 Section on Clinical Bsain Imaging, Lab of Psychology & Psychopathology, NIMH, Bethesda, MD., Section tn Clinical Studies, Clinical Neuroscience Branch, NIMH, Bethesda, MD., Clinical Neuropharmacology Branch, NIMH, Bethesda, MD. /Reprint requests to MC/
ABSTRACT Utilizing a double-blind crossover design, the hormonal effects of high dose, 2 mg/kg, were compared to low dose, 0.4 mg (approx. 5 ug/kg), naloxone administration in physically healthy humans. A significant naloxone dose effect on plasma cortisol levels was found (pUl.OOl), but no significant effect on plasma or serum levels of prolactin, follicle stimulating hormone, luteinizing hormone, norepinephrine or epinephrine. These results confirm involvement of the endogenous opioid system (EOS) in the tonic regulation of the hypothalamicpituitary-adrenalaxis, but fail to find evidence of EOS involvement in the regulation of adrenal medullary function or the gonadotrophic axis in man. The results are however consistent with a continuing action of naloxone as an EOS antagonist even at high doses in man.
INTRODUCTION The discovery of the endogenous opioid system (EOS) has led to an intensive investigation of its potential importance in human physiology (I-11). Alterations in physiologic parameters following the administration of opioids in humans support this potential (12-17). However, effects following the administration of naloxone, a drug which is assumed to block the functioning of the EOS would provide more direct evidence of the system's current functioning and importance (18). We have noted in greater detail elsewhere that many clinical studies with naloxone may have used an insufficient dose to assure functional blockade of all relevant EOS's (18). In a study utilizing a single-blind design, we reported blood pressure and behavioral effects of naloxone, when administered in the mg/kg range to humans, that were not evident in previous studies using lower doses of naloxone (18,19). With the exception of our preliminary 373
single-blind study, previous studies of hormonal effects of naloxone administration in humans have used low dcses (less than or equal to 0.5 mg/kg) (2, In this study, we evaluate the hormonal consequences of a high 7,16,20,21). dose (2mg/kg) compared to a low dose (approximately 5 ug/kg) of naloxone using a double-blind crossover design. METHODS Hormonal effects were evaluated in eight women and six men (n=14) aged 19 to 56 years, free of systemic physical illness. All gave informed consent prior to their participation; all were free of drugs for at least 3 days prior to their study and free from opiates for at least the 3 preceeding Seven of the volunteers at the time of the study were suffering from weeks. mental disorders, three from major depression and four from schizophrenia (DSM III criteria). Patients who had been on a chronic medication regime had been withdrawn from all drugs at least 2 weeks prior to their study. By exclusion, no subject had a history of drug or alcohol abuse. The study utilized a double-blind, random but balanced crossover design so that each volunteer or patient was administered 2 mg/kg or 0.4 mg. (approximately 5 ugfkg) of naloxone intravenously (iv) on separate days at least 72 hours apart. Each day began at 0830 hours following an overnight A catheter was placed in an arm vein and kept patent with heparin. At fast. 0920, 0.4 mg. naloxone (a test dose) was administered iv to eliminate the possibility of undetected or recent opiate intake by a volunteer. This use could have led to a severe withdrawal reaction following the administration of a high dose of naloxone as well as complicate any conclusions regarding the effect of a high dose of naloxone on the EOS. The 0.4 mg. naloxone should not have added significantly to the following 2 mg/kg dose. Only after this low dose of naloxone failed to produce effects of opiate withdrawal (as was always the case) was an iv infusion (double-blind dose) of 2 mg/kg naloxone dissolved in less than 20 cc normal saline vehicle or a normal saline vehicle of equal volume (placebo) administered over less than 2 Thus, although a placebo was used to blind the minutes at 0930 hours. there was no day during which the administration of high dose naloxone, subject received placebo alone. Subjects were required to lie in a supine position for a brief period of time prior to and following their infusions (from 0915 until 1000 hours) and for 5 minutes prior to the withdrawal of each blood sample. Subjects were not permitted to eat during the testing period; otherwise, activity that was not physically strenuous was permitted. Blood samples were obtained for hormonal evaluations immediately prior and at 0.5, 1 and 2 hours to the 0.4 mg naloxone test infusion (0, baseline) Samples were immediately split for the following the double-blind infusion. Blood for plasma preparation was separate preparation of plasma and serum. placed on ice; within 30 minutes plasma was obtained by centrifugation for 15 minutes at 3,000 rpms (O-4’ C) and aliquots were frozen at (-80” C) for Serum was obtained by allowing the blood to clot at room future assay. subsequent handling was the same as for the plasma preparation. temperature-; Hormone determinations were conducted using commercially supplied reagents were obtained from New England Nuclear; For cortisol, agents. 374
refor
prolactin, follicle stimulating hormone (FSH), and luteinizing hormone (LH) reagents were obtained from Immuno Nuclear. The hormone responses of an individual on both days of the study were always determined within the same assay. Intra-assay coefficients of variation was 6% or less; inter-assay variation was less than 10%. Plasma epinephrine and norepinephrine were measured by high-pressure liquid chromatography with electrochemical detection (22). Statistical analysis of the effect of naloxone dose on plasma or serum hormone levels was accomplished using repeated measures analysis of variance (anovar). The degrees of freedom sometimes varied with the analysis of a given hormone because technical limitations sometimes decreased the study There was no correlation of hormone sample size from N=14 (but always N>9). responses with age, sex or psychiatric diagnosis. However, in the evaluation of the naloxone dose effect on serum prolactin levels, the study sample excluded patients with depression. Previous reports have suggested an abnormal lack of responsiveness of serum prolactin levels to opioid agonists in depression (23,24). Prolactin measurements were accomplished at baseline, 0.5 and 1 hour post infusion since our previous single blind study had suggested that a naloxone dose effect on prolactin would be most likely to occur within this first hour (18). RESULTS The mean + SEM of the measured plasma and serum hormone levels are presented in Table I. Only plasma cortisol levels were found to be significantly affected by naloxone dose. Evaluation of individual cortisol responses established the consistency of the response. Thirteen of fourteen subjects showed a greater maximum change in plasma cortisol levels during the high compared to the low dose naloxone day. In the case of the gonadotrophic hormones, we evaluated the possibility that there might be differences in the hormonal responses of men and women that might obscure a naloxone dose effect but found no significant effect of sex on either the FSH or LH response. DISCUSSION An increase in plasma cortisol levels following high dose naloxone administration is consistent with results from previous human studies of the effects of low doses of naloxone (6,8,21,25) as well as with reports of plasma cortisol suppression following opioid agonist administration (25-28). The data is entirely consistent with the hypothesis that the EOS is actively involved in the tonic regulation of plasma cortisol levels in humans. In contrast to cortisol, serum prolactin was found not to be significantly affected by naloxone dose. This result is consistent with our previous singleblind study of high dose naloxone administration as well as with previous low dose studies in humans which in the great majority have found no alteration of prolactin levels with naloxone administration (6,9, 29). These results are not consistent with EOS involvement in the tonic regulation of serum prolactin levels. Nevertheless, the potential for EOS involvement in the regulation of prolactin secretion under special circumstances is suggested by the increase in serum prolactin levels that is found
375
during human adaptation to stress (30) and following opioid agonist administration in humans (23,24,28).
TABLE I Effect of Naloxone Dose on Serum or Plasma Hormone Concentrations (MeanfSEM)
Hormone (units)
0.4 mg (approx.Sug/kg)
0
2 mg/kg Dose
(Hrs. post-infusion) 0.5 1 2
0
No.of Subjects
Significance
(Hrs. post-infusion) 0.5 1 2
Cortisol (ugX)
11.9 21.1
10.0 21.1
10.3 9.8 +1.5 21.3
12.6 +1.1
18.8 19.4 16.9 21.5 +1.2 +1.8
PRL (r&ml)
12.2 +3.0
10.3 22.1
8.7 t1.6
12.5 +3.0
14.7 24.7
13.3 23.7
LH (mIu/ml)
2.1 20.7
1.6 20.7
3.1 2.4 20.6 to.7
2.0 20.5
2.5 to.6
FSH (mIu/ml)
2.9 to.7
3.4 to.7
3.7 3.7 20.8 20.7
4.0 20.7
3.2 to.8
Epinephrine (pglml)
182 ?56
124 237
145 +46
141 +43
114 226
163 241
149 f42
Norepinephrine(pg/ml)
219 +27
201 +29
213 +35
255 ?45
161 214
140 ?18
168 221
14
&O.OOl*
9
NS+
3.9 3.0 20.7 to.5
14
NS+
4.0 3.2 fl.1 to.9
14
NS
109 ?32
10
NS
157 +18
10
NS
* Significant main effect for dose,F=l9.7 (df=1,13); significant interaction effect for dose x hour, F=ll.S (df=3,39) + NS3p70.1 for main or interaction effects
The results of animal studies have suggested the possible importance of the EOS in the regulation of gonadotrophic hormone secretion in humans (31, 32). In clinical studies opioid agonists have been demonstrated to acutely depress serum gonadotrophic levels (31). However, in this study we have not been able to find evidence to suggest EOS involvement in the regulation of either tonic FSH or LH secretion. In addition, we found no evidence of an effect of sex on the gonadotrophic hormone response to naloxone to explain the previously reported finding of increased serum LH levels in men following naltrexone administration (33). The difference in results may perhaps be attributed to an agonist effect of naltrexone at an opiate receptor subtype or to the more frequent (20x) and longer duration (8 hours) of the blood sampling for this episodically secreted hormone in the latter study. Cur findings suggest that future studies might require a more intensive and perhaps prolonged evaluation of gonadotrophin levels and/or be directed to
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understanding the possible involvement of the EOS in episodic alterations of gonadotrophic secretion, as for example those that occur during temporal periods of the menstrual cycle or during menarche or menopause. This suggestion is consistent with previous findings that naloxone administration over a 6 hour period produced in young women an increase in episodic LH secretion during the midluteul phase (days 18-21) of the menstrual cycle but had no effect on secretion in the follicular phase or in post menopausal women (34,35). EOS involvement in adrenal medullary function has been suggested in In addition, a recent case report has suggested that animal studies (36). low dose naloxone administration may increase plasma epinephrine and norepinephrine levels in patients suffering from pheochromocytoma (37). We have previously reported an increase in systolic blood pressure in humans following the administration of increasing doses of naloxone in the mg/kg range In this study, however, we were unable to find any evidence to support (19). EOS involvement in the tonic regulation of human plasma norepinephrine or epinephrine levels. In summary, our results confirm an important role for the EOS in the tonic regulation of plasma cortisol levels in humans, but suggest a lack of involvement of the EOS in the tonic regulation of plasma or serum levels of prolactin, FSH, LH, norepinephrine or epinephrine levels in humans. However, although relatively high doses of naloxone were used in this study, higher doses or more prolonged naloxone administration may yet be required to ensure sufficient functional blockade to rule out EOS involvement in the tonic regulation of these hormone levels. The dose chosen for this study was the maximum, however, we felt could be acutely administered with a minimal of somatic complaints that might indirectly effect hormone function and/or break the blind design. The findings of this study support the conclusion that naloxone administration even at high doses in humans is without agonist activity, since the expected effects of an opioid agonist i.e. suppression of serum FSH and LH levels and an increase in serum prolactin levels were not observed. Thus, understanding of EOS involvement in episodic hormone alterations such as during human stress responses may be clarified by using a range of doses of naloxone to include doses in the mg/kg range to assure functional blockade of all relevant EOSs. REFERENCES 1.
D. and Dubois, M. (1983). The role of the Cohen, M.R., Pickar, endogenous opioid system in the human stress response. Psychiatric Clinics of North America 6: 457-471.
2.
N. and Blichert-Toft, M. (1981). Engquist, A., Hicquet, J., Saurbrey, and hemodynamic response to surgery after naloxone Cortisol, glucose, Acta Anaesthesiologica Scandinavica 25: 17-20. administration.
3.
Grevert, P. and Goldstein, A. (1978). experimental pain or mood in humans.
4.
Jones,
R. and Herning,
R.
(1979).
Naloxone fails to alter Science 199: 1093-1095,
Naloxone
377
induced
mood and physiologic
changes in normal volunteers In: Usdin, E., Bunney, W.E. and Kline, N. (eds.) Endorphins in Mental Health Research. Oxford University Press, New York, p. 484-491. 5.
Judd, L., Janowsky, D., Segal, D. and Huey, L.Y. (1980). Naloxoneinduced behavioral and physiological effects in normals and manic subjects. Archives of General Psychiatry 37: 583-586.
6.
Naber, D., Pickar, D., Davis, G., Cohen, R.M., Jimerson, D.C. Elchisak, M.A., Defraites, E.G., Kalin, N.H., Risch, S.C. and Buchsbaum, M.S. (1981). Naloxone effects on beta-endorphin, cortisol, prolactin, growth hormone, HVA & MHPG in plasma of normal volunteers. Psychopharmacology 74: 125-128.
7.
Spiler, I. and Molitch, M. (1980). Lack of modulation of pituitary hormone stress response by neutral pathways involving opiate receptors. Journal of Clinical Endocrinology and Metabalism 50: 516-520.
8.
Volavka, J., James, B., Reker, D., Pollock V. and Cho, D. (1979). Electroencepholographic and other effects of naloxone in normal men. Life Sciences 25: 1267-1272.
9.
Volavka, J., Bauman, J., Pevnick, J., Reker, D., James, B. and Cho., D. (1980). Short-term effects of naloxone in man. Psychoneuroendrocrinology 5: 225-234.
10. Wilier, J.C., Boureau, F., Dauthier C. and Bonora, M. (1979). Study of naloxone in normal awake man: effects on heart rate and respiration. Neuropharmacology 18: 469-572. 11. Zilm, D.H. (1980). Naloxone response in non-dependent man: effect on six physiological variables. Neuropharmacology 19: 591-595. 12. Brandt, M.R., Korshin, J., Hensen, A.P., Hummer, L. and Madsen, S.N. (1978). Influence of morphine anaesthesia on the endocrine-metabolic response to open-heart surgery. Acta Anesthesiologica Scandinavica 2: 400-412. 13.
Dubois, M., Pickar, D., Cohen, M.R., Gadde, P., Macnamara, T.E. and Bunney, W.E. (1982). Effects of fentanyl on the response of plasma beta-endorphin immunoreactivity to surgery. Anesthesiology 57: 468-472.
14.
Foley, K.M., Kourides, I.A., Inturrisi, C.E., Kaiko, R.F., Zaroulis, C.G., Posner, J.B., Houde, R.W. and Li, C.H. (1979). Beta-endorphin: Analgesic and hormonal effects in humans. Proceedings of the National Academy of Sciences of the USA 76: 5377-5381.
15. Jaffe, J. and Martin, W. (1975). Narcotic analgesics and antagonists. In: Goodman, L. and Gilman, A. (eds.) The Pharmacological Basis of Therapeutics. Macmillan, New York, p. 245-283. 16. Martin, W. and Jasinski, D. (1969). Physiological parameters of morphine dependence in man-tolerence, early abstinence protractual abstinence. Journal of Psychiatry Research 7: 9-17.
378
17. Tolis, G., Hickey, J. and Guyda, H. (1975). Effects of morphine on serum growth hormone, cortisol, prolactin and thyroid stimulating hormone in man. Journal of Clinical Endocrinology Metabolism 41: 797-800. 18. Cohen, M.R., Cohen, R.M., Pickar, D., Weingartner, H. and Murphy, D.L. (1983). High dose naloxone infusions in normals: dose-dependent behavioral, hormonal and physiological responses. Archives of General Psychiatry 40: 613-619. 19. Cohen, M.R., Cohen, R.M., Pickar, D., Murphy, D. and Bunney, W. (1982). Physiological effects of high dose naloxone administration to normal adults. Life Sciences 30: 2025-2031. 20.
Janowsky D., Judd, L., Huey, L., Roitman, N., Parker, D. and Segal, D. (1978). Naloxone effects on manic symptoms and growth hormone levels. Lancer 2: 320.
21. Morley, J.E., Baranetsky, N.G., Wingert, T.D., Carlson, H., Hershman, S. Melmed, S., Levin, S., Jamison, K. and Weitzman, R. (1980). Endocrine effects of naloxone-induced opiate receptor blockade. Journal of Clinical Endocrinol Metabolism 50: 251-257. 22.
Chiueh, C., Zukowska-Grojec, K., Kirk, K.L. and Kopin, I.J. (1983). 6-Fluorocatecholamines as false adrenergic neurotransmiters. Journal Pharmacology and Experimental Therapeutics 225: 529-33.
23.
Extein, I., Pottash, A., Gold, M., Sweeney, D., Martin, D. and Goodwin, F. (1980). Deficient prolactin response to morphine in depressed patients. American Journal of Psychiatry 137: 845-846.
24.
Judd, L., Risch, S., Parker, D., Janowsky, D., Segal, D. and Huey, L. (1982). Blunted prolactin response. A neuroendocrine abnormality manifested by depressed patients. Archives of General Psychiatry 39: 1413-1416.
25.
Judd, L. and Janowsky, D.S. (1981). Effects of narcotics and narcotic antagonists on affective disorders, schizophrenia and serum neurohormones. Modern Problems of Pharmacopsychiatry 17: 213-225.
26.
Gold, P., Extein, I,, Pickar, D., Ross, R. and Goodwin, F. (1980). Suppression of plasma cortisol in depressed patients by acute intravenous methadone infusion. American Journal of Psychiatry 137: 862-863.
27.
Judd, L., Parker, D., Janowsky, D., Segal, D., Risen, S. and Huey., L. (1982). The effect of methadone on the behavioral and neuroendocrine responses of manic patients. Psychiatry Research 7: 163-70.
28.
Pickar, D., Davis, G.C., Schulz, C.S., Extein, I., Wagner, R., Naber, D. Gold, P.W., van Kammen, D.P., Goodwin, F.K., Wyatt, R.J., Li, C.H. and Bunney, W.E. (1981). Behavioral and biological effects of acute betaendorphin injection in schizophrenic and depressed subjects. American Journal of Psychiatry 138: 160-166.
379
29.
Janowsky, D., Judd, L., Huey, L., Roitman, N. and Parker, D. (1979). Naloxone effects on serum growth hormone and prolactin in man. Psychopharmacology 65: 95-97.
30.
Boyd, A. and Reichlin, S. (1977). Neural Control of prolactin secretion in man. Psychoneuroendrocrinology 3: 113-130.
31.
Cicero, T. (1980). Effects of exogenous and endogenous opiates on the hypothamalic-pituitary-gonadalaxis in the male. Federation Proceedings 39: 2551-2554.
32.
Van Vugt, D. and Meites., J. (1980). Influence of endogenous opiates on anterior pituitary function. Federation Proceedings 39: 2533-2538.
33. Mendelson, J., Ellingboe, J., Keuhnle J. and Mello, N. (1979). Effects of naltrexone on mood and neuroendocrine function in normal adult males. Psychoneuroendocrinology 3: 231-236. 34.
Reid, E.L., Quigley, M.E. and Yen, S.S. (1983). The disappearance of opioidergic regulation of gonadotropin secretion in postmenopausal women. Journal of Clinical Endocrinology and Metabolism 57: 1107-1110.
35.
Ropert, J.F., Quigley, M.E. and Yen, S.S. (1981). Endogenous opiates modulate pulsatile luteninizing hormone release in humans. Journal of Clinical Endocrinology and Metabolism 52: 583-585.
36.
Amir, S., Brown, 2. and Amit, 2. (1979). The role of endorphins in stress: evidence and speculations. Neuroscience and Biobehavioral Reviews 4: 77-86.
37. Mannelli, M., Maggi, M., Defeo, M.L., Cuomo, S., Forti, G., Moroni, F. and Giusti, G. (1983). Naloxone administration releases catecholamines. New England Journal of Medicine 308: 654-655.
Accepted 7/6/85
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