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Repeated central administration of α-MSH does not alter the antipyretic effect of α-MSH in young and aged rabbits
Peptides. Vol. 10, pp. 697-699. ©Pergamon Press plc, 1989. Printed in the U.S.A.
0196-9781/89 $3.00 + .00
BRIEF COMMUNICATION
Repeated Central Administration of oL-MSH Does not Alter the Antipyretic Effect of oL-MSH in Young and Aged Rabbits L. B. D E E T E R , * L. W . M A R T I N * A N D J. M . L I P T O N * t 1
Departments o f *Physiology and fAnesthesiology The University of Texas Southwestern Medical Center at Dallas 5323 Harry Hines Boulevard, Dallas, TX 75235-9040 R e c e i v e d 4 N o v e m b e r 1988
DEETER, L. B., L. W. MARTIN AND J. M. LIPTON. Repeatedcentral administration of e~-MSHdoes not alter the antipyretic effect of a-MSH in young and aged rabbits. PEPTIDES 10(3) 697-699, 1989.--a-Melanocyte-stimulating hormone is a potent antipyretic when administered centrally or peripherally; however, there are no previous data on development of tolerance to the antipyretic action of this neuropeptide. In previous research, aged rabbits were more sensitive to low doses of c~-MSH than young rabbits. We tested the antipyretic action of oL-MSH in young and old rabbits after twice daily injections of the peptide for 10 days. Neither aged nor younger rabbits showed altered responses to a-MSH. This lack of tolerance underscores the importance of a-MSH to physiological control and survival of the host. a-MSH
Antipyretic
Aging
Fever
Tolerance
the start of experimentation. To measure the febrile response, a thermistor probe (Yellow Springs International, No. 701) was inserted 10 cm into the rectum of each rabbit and secured with tape. Body temperature was recorded at 10-min intervals with a MINC I 1 on-line computer connected to a digital temperature recorder (Datalogger, Digital Electronics). To establish a stable baseline temperature, a minimum of 1 hr was allowed prior to any injections. All doses of et-MSH were given in 50 txl nonpyrogenic saline followed by a 20 1 saline flush, and all saline control injections were 70 p,1 in volume. Five hundred ng ot-MSH was selected in preexperimental trials as the dose needed to reduce interleukin-1 fever 50% in young male rabbits. Crude IL-1 was made by incubating rabbit white blood cells with Salmonella typhosa lipopolysaccharide (5). The rabbits were randomly assigned to one of two groups: old ( 3 - 5 + years) or young ( < 2 years). To establish doses of IL-1 before exposure to oL-MSH, the rabbits were initially made febrile by IV injection of IL-1 in doses sufficient to raise rectal temperature at least 0.7°C, typically 40 to 80 ixl/kg. After an interval of 3 days or more, they were again given IL-1 and 500 ng ct-MSH
et-MELANOCYTE-stimulating hormone (oL-MSH) is a potent antipyretic when administered centrally, intravenously, or intragastrically (5, 6, 12, 13). The concentration of ot-MSH in the septum, an area of the brain involved in thermoregulation, increases during fever (15), and injections of ct-MSH into the septal region reduce fever (6). Since ct-MSH may prove to be a clinically useful antipyretic, it is important to know if repeated central administration of the peptide results in tolerance to its antipyretic effect. Tolerance to the thermoregulatory effects of morphine is reduced in aged rats (10) and this observation led us to investigate the possibility that tolerance to et-MSH is age-dependent as well. METHOD New Zealand white rabbits were housed individually in a 21-23°C environment with a 12-hr light-dark cycle and food and water available ad lib. A stainless steel cannula (David Kopf Instruments, No. 201) was surgically placed into a lateral cerebral ventricle (17). At least 7 days were allowed between surgery and
1Requests for reprints should be addressed to J. M. Lipton, Ph.D.
697
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FIG. 1. ICV administration of (A) 500 ng c~-MSHor (B) saline twice daily for 10 days did not significantly alter the antipyretic effect of a-MSH in young rabbits (<2 years). (%a-MSH injection is indicated by the arrow. Values are means - S.E.M.
FIG. 2. ICV administration of (A) 500 mg a-MSH or (B) saline twice daily for 10 days did not significantly after the antipyretic effect of a-MSH in old rabbits (3-5+ years), a-MSH injection is indicated by the arrow. Values are means _+S.E.M.
was injected intracerebroventricularly (ICV) 30 min later to determine the antipyretic response to the peptide (pretest). The rabbits were then given either saline or 500 ng (x-MSH ICV twice daily at 9 a.m. and 5 p.m. for 10 days, after which the antipyretic response to (x-MSH was reevaluated (posttest). After a 10-day rest period, the pretest was readministered. The rabbits that had previously received saline were then given a-MSH for 10 days, and those animals receiving ot-MSH earlier were given saline. Ten days later, the posttest was given. Wherever possible, the same rabbits were used for saline and o~-MSH injections. The magnitude of the fever was calculated as the area under the fever curve (>°C × hr) over 4 hr (3) and an analysis of variance (F-test) was performed on the pre- and posttest data.
undesirable side-effect of stimulating corticosterone release when administered repeatedly. Repeated administration of a-MSH has no effect on plasma levels of corticosterone (14), so it may be possible to reduce fever with multiple injections of o~-MSH without causing the clinical and metabolic disorders, e.g., Cushing's syndrome, associated with ACTH treatment. There is evidence that chronic administration of et-MSH in large doses does increase aldosterone levels in vivo (11,14), but there is also a report of reduced aldosterone levels following long-term administration of the peptide (4). 13-Endorphin, which shares the proopiomelanocortin precursor with ot-MSH and ACTH, has analgesic, behavioral, and thermoregulatory effects when given ICV. Tolerance to all of these effects has been demonstrated after single dose or long-term administration of f3-endorphin (2, 7, 8, 16). The mechanism of 13-endorphin tolerance appears to be very similar to that of morphine tolerance, and cross-tolerance to morphine has been demonstrated (7, 8, 16). Even though 13-endorphin and a-MSH have a common precursor and both exhibit thermoregulatory effects, the tolerance that is seen with ICV injections of I~endorphin does not occur in either old or young rabbits with repeated ICV administration of o~-MSH. Continued sensitivity despite repeated exposure to the peptide suggests that the ability to respond to central ot-MSH is very important to both young and old animals.
RESULTS AND DISCUSSION
Repeated ICV injections of 500 ng a-MSH or saline did not significantly alter the antipyretic response of either the young or old rabbits to o~-MSH [young, ot-MSH: F(10,10)=0.07, p>0.75; young, saline: F(13,13) = 0.10, p>0.75; old, a-MSH: F(8,8) = 0.45, p>0.50; old, saline: F(8,8)=0.02, p>0.80]. Unlike earlier findings (1,9), in this experiment, old rabbits were not more sensitive to ot-MSH than young rabbits (young, 57% reduction; old, 62% reduction; Student's t-test, p > 0 . 6 ) , possibly because of the relatively large dose of o~-MSH used. Increased sensitivity to et-MSH with aging is more marked with low doses of the peptide (1,9). Although ACTH, which shares the 1-13 amino acid sequence with a-MSH, is a more potent antipyretic than a-MSH, it has the
ACKNOWLEDGEMENTS This research was supported by Grant AG00109 from the National Institute on Aging and Grant NS10046 from the National Institute of Neurological and Communicative Disorders and Stroke.
REPEATED ADMINISTRATION OF tx-MSH
699
REFERENCES 1. Bell, R. E.; Feng, J.; Lipton, J. M. Is the endogenous antipyretic neuropeptide tx-MSH responsible for reduced fever in aged rabbits? Peptides 8:501-504; 1987. 2. Bhargava, H. N. Inhibition of tolerance to the pharmacological effects of human 13-endorphinby prolyl-leucyl-glycinamide and cyclo (leucylglycine) in the rat. J. Pharmacol. Exp. Ther. 218:404--408; 1981. 3. Clark, W. G.; Holdeman, M.; Lipton, J. M. Analysis of the antipyretic action of a-melanocyte-stimulation hormone in rabbits. J. Physiol. 359:459-465; 1985. 4. Gangnly,G.; Hampton, T.; Sumpter, D.; Chiou, S. Impaired aldosterone secretion from dispersed adrenal capsular cells of chronically a-MSH-treated rats. Steroids 47:261-268; 1986. 5. Glyn, J. R.; Lipton, J. M. Hypothermic and antipyretic effects of centrally administered ACTH (1-24) and a-melanotropin. Peptides 2:177-187; 1981. 6. Glyn-Ballinger, J. R.; Bernardini, G. L.; Lipton, J. M. ot-MSH injected into the septal region reduces fever in rabbits. Peptides 4:199-203; 1983. 7. Huidobro-Toro, J. P.; Way, E. L. Rapid development of tolerance to the hyperthermic effect of I~-endorphin, and cross-tolerance between the enkephalins and fl-endorphin. Eur. J. Pharmacol. 65:221-231; 1980. 8. Huidobro-Toro, J. P.; Way, E. L. Single-dose tolerance to antinociception, and physical dependence on 13-endorphin in mice. Eur. J. Pharmacol. 52:179-189; 1978. 9. Lipton, J. M.; Murphy, M. T. Aging enhances the antipyretic effect of a-MSH and the hyperthermic effect of central 13-endorphin. In:
10.
11.
12. 13.
14.
15.
16.
17.
Lomax, P.; Schonbaum, E., eds. Environment, drugs and thermoregulation. Basel: S. Karger; 1983:104-107. McDougal, J. N.; Marques, P. R.; Burke, T. F. Reduced tolerance to morphine thermoregulatory effects in senescent rats. Life Sci. 28(2): 137-145; 1981. Mazzocchi, G.; Malendowicz, L. K.; Gottardo, G.; Nussdorfer, G. G. Evidence that prolonged et-MSH infusion enhances the steroidogesic capacity of rat adrenal zona glomerulosa in vivo. J. Steroid Biochem. 29(4):441-442; 1988. Murphy, M. T.; Lipton, J. M. Peripheral administration of ~t-MSH reduces fever in older and younger rabbits. Peptides 3:775-779; 1982. Murphy, M. T.; Richard, D. B.; Lipton, J. M. Antipyretic potency of centrally administered ct-melanocyte-stimulating hormone. Science 221:192-193; 1983. Robba,C.; Rebuffat, R.; Mazzocchi, G.; Nussadorfer, G. C. Longterm trophic action of tx-melanocyte-stimulating hormone on the zona glomerulosa of the rat adrenal cortex. Acta Endocrinol. 112:404---408; 1986. Samson, W. K.; Lipton, J. M.; Zimmer, J. A.; Glyn, J. R. The effect of fever on central ct-MSH concentration in the rabbit. Peptides 2:419-423; 1981. Tseng, L.; Loh, H. H.; Li, C. H. Human 13-endorphin: development of tolerance and behavioral activity in rats. Biochem. Biophys. Res. Commun. 74(2):390-396; 1977. Williams, D. W., Jr.; Lipton, J. M.; Giesecke, A. H., Jr. Influence of centrally administered peptides on ear withdrawal in the rabbit. Peptides 7:1095-1100; 1986.
0196-9781/89 $3.00 + .00
BRIEF COMMUNICATION
Repeated Central Administration of oL-MSH Does not Alter the Antipyretic Effect of oL-MSH in Young and Aged Rabbits L. B. D E E T E R , * L. W . M A R T I N * A N D J. M . L I P T O N * t 1
Departments o f *Physiology and fAnesthesiology The University of Texas Southwestern Medical Center at Dallas 5323 Harry Hines Boulevard, Dallas, TX 75235-9040 R e c e i v e d 4 N o v e m b e r 1988
DEETER, L. B., L. W. MARTIN AND J. M. LIPTON. Repeatedcentral administration of e~-MSHdoes not alter the antipyretic effect of a-MSH in young and aged rabbits. PEPTIDES 10(3) 697-699, 1989.--a-Melanocyte-stimulating hormone is a potent antipyretic when administered centrally or peripherally; however, there are no previous data on development of tolerance to the antipyretic action of this neuropeptide. In previous research, aged rabbits were more sensitive to low doses of c~-MSH than young rabbits. We tested the antipyretic action of oL-MSH in young and old rabbits after twice daily injections of the peptide for 10 days. Neither aged nor younger rabbits showed altered responses to a-MSH. This lack of tolerance underscores the importance of a-MSH to physiological control and survival of the host. a-MSH
Antipyretic
Aging
Fever
Tolerance
the start of experimentation. To measure the febrile response, a thermistor probe (Yellow Springs International, No. 701) was inserted 10 cm into the rectum of each rabbit and secured with tape. Body temperature was recorded at 10-min intervals with a MINC I 1 on-line computer connected to a digital temperature recorder (Datalogger, Digital Electronics). To establish a stable baseline temperature, a minimum of 1 hr was allowed prior to any injections. All doses of et-MSH were given in 50 txl nonpyrogenic saline followed by a 20 1 saline flush, and all saline control injections were 70 p,1 in volume. Five hundred ng ot-MSH was selected in preexperimental trials as the dose needed to reduce interleukin-1 fever 50% in young male rabbits. Crude IL-1 was made by incubating rabbit white blood cells with Salmonella typhosa lipopolysaccharide (5). The rabbits were randomly assigned to one of two groups: old ( 3 - 5 + years) or young ( < 2 years). To establish doses of IL-1 before exposure to oL-MSH, the rabbits were initially made febrile by IV injection of IL-1 in doses sufficient to raise rectal temperature at least 0.7°C, typically 40 to 80 ixl/kg. After an interval of 3 days or more, they were again given IL-1 and 500 ng ct-MSH
et-MELANOCYTE-stimulating hormone (oL-MSH) is a potent antipyretic when administered centrally, intravenously, or intragastrically (5, 6, 12, 13). The concentration of ot-MSH in the septum, an area of the brain involved in thermoregulation, increases during fever (15), and injections of ct-MSH into the septal region reduce fever (6). Since ct-MSH may prove to be a clinically useful antipyretic, it is important to know if repeated central administration of the peptide results in tolerance to its antipyretic effect. Tolerance to the thermoregulatory effects of morphine is reduced in aged rats (10) and this observation led us to investigate the possibility that tolerance to et-MSH is age-dependent as well. METHOD New Zealand white rabbits were housed individually in a 21-23°C environment with a 12-hr light-dark cycle and food and water available ad lib. A stainless steel cannula (David Kopf Instruments, No. 201) was surgically placed into a lateral cerebral ventricle (17). At least 7 days were allowed between surgery and
1Requests for reprints should be addressed to J. M. Lipton, Ph.D.
697
698
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~'
~
t.0
N=11
pre-test~ l ~ post-test A - - A
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H o u r s After IL-t Injection
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I
I
4
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H o u r s A f t e r IL-I Injection
FIG. 1. ICV administration of (A) 500 ng c~-MSHor (B) saline twice daily for 10 days did not significantly alter the antipyretic effect of a-MSH in young rabbits (<2 years). (%a-MSH injection is indicated by the arrow. Values are means - S.E.M.
FIG. 2. ICV administration of (A) 500 mg a-MSH or (B) saline twice daily for 10 days did not significantly after the antipyretic effect of a-MSH in old rabbits (3-5+ years), a-MSH injection is indicated by the arrow. Values are means _+S.E.M.
was injected intracerebroventricularly (ICV) 30 min later to determine the antipyretic response to the peptide (pretest). The rabbits were then given either saline or 500 ng (x-MSH ICV twice daily at 9 a.m. and 5 p.m. for 10 days, after which the antipyretic response to (x-MSH was reevaluated (posttest). After a 10-day rest period, the pretest was readministered. The rabbits that had previously received saline were then given a-MSH for 10 days, and those animals receiving ot-MSH earlier were given saline. Ten days later, the posttest was given. Wherever possible, the same rabbits were used for saline and o~-MSH injections. The magnitude of the fever was calculated as the area under the fever curve (>°C × hr) over 4 hr (3) and an analysis of variance (F-test) was performed on the pre- and posttest data.
undesirable side-effect of stimulating corticosterone release when administered repeatedly. Repeated administration of a-MSH has no effect on plasma levels of corticosterone (14), so it may be possible to reduce fever with multiple injections of o~-MSH without causing the clinical and metabolic disorders, e.g., Cushing's syndrome, associated with ACTH treatment. There is evidence that chronic administration of et-MSH in large doses does increase aldosterone levels in vivo (11,14), but there is also a report of reduced aldosterone levels following long-term administration of the peptide (4). 13-Endorphin, which shares the proopiomelanocortin precursor with ot-MSH and ACTH, has analgesic, behavioral, and thermoregulatory effects when given ICV. Tolerance to all of these effects has been demonstrated after single dose or long-term administration of f3-endorphin (2, 7, 8, 16). The mechanism of 13-endorphin tolerance appears to be very similar to that of morphine tolerance, and cross-tolerance to morphine has been demonstrated (7, 8, 16). Even though 13-endorphin and a-MSH have a common precursor and both exhibit thermoregulatory effects, the tolerance that is seen with ICV injections of I~endorphin does not occur in either old or young rabbits with repeated ICV administration of o~-MSH. Continued sensitivity despite repeated exposure to the peptide suggests that the ability to respond to central ot-MSH is very important to both young and old animals.
RESULTS AND DISCUSSION
Repeated ICV injections of 500 ng a-MSH or saline did not significantly alter the antipyretic response of either the young or old rabbits to o~-MSH [young, ot-MSH: F(10,10)=0.07, p>0.75; young, saline: F(13,13) = 0.10, p>0.75; old, a-MSH: F(8,8) = 0.45, p>0.50; old, saline: F(8,8)=0.02, p>0.80]. Unlike earlier findings (1,9), in this experiment, old rabbits were not more sensitive to ot-MSH than young rabbits (young, 57% reduction; old, 62% reduction; Student's t-test, p > 0 . 6 ) , possibly because of the relatively large dose of o~-MSH used. Increased sensitivity to et-MSH with aging is more marked with low doses of the peptide (1,9). Although ACTH, which shares the 1-13 amino acid sequence with a-MSH, is a more potent antipyretic than a-MSH, it has the
ACKNOWLEDGEMENTS This research was supported by Grant AG00109 from the National Institute on Aging and Grant NS10046 from the National Institute of Neurological and Communicative Disorders and Stroke.
REPEATED ADMINISTRATION OF tx-MSH
699
REFERENCES 1. Bell, R. E.; Feng, J.; Lipton, J. M. Is the endogenous antipyretic neuropeptide tx-MSH responsible for reduced fever in aged rabbits? Peptides 8:501-504; 1987. 2. Bhargava, H. N. Inhibition of tolerance to the pharmacological effects of human 13-endorphinby prolyl-leucyl-glycinamide and cyclo (leucylglycine) in the rat. J. Pharmacol. Exp. Ther. 218:404--408; 1981. 3. Clark, W. G.; Holdeman, M.; Lipton, J. M. Analysis of the antipyretic action of a-melanocyte-stimulation hormone in rabbits. J. Physiol. 359:459-465; 1985. 4. Gangnly,G.; Hampton, T.; Sumpter, D.; Chiou, S. Impaired aldosterone secretion from dispersed adrenal capsular cells of chronically a-MSH-treated rats. Steroids 47:261-268; 1986. 5. Glyn, J. R.; Lipton, J. M. Hypothermic and antipyretic effects of centrally administered ACTH (1-24) and a-melanotropin. Peptides 2:177-187; 1981. 6. Glyn-Ballinger, J. R.; Bernardini, G. L.; Lipton, J. M. ot-MSH injected into the septal region reduces fever in rabbits. Peptides 4:199-203; 1983. 7. Huidobro-Toro, J. P.; Way, E. L. Rapid development of tolerance to the hyperthermic effect of I~-endorphin, and cross-tolerance between the enkephalins and fl-endorphin. Eur. J. Pharmacol. 65:221-231; 1980. 8. Huidobro-Toro, J. P.; Way, E. L. Single-dose tolerance to antinociception, and physical dependence on 13-endorphin in mice. Eur. J. Pharmacol. 52:179-189; 1978. 9. Lipton, J. M.; Murphy, M. T. Aging enhances the antipyretic effect of a-MSH and the hyperthermic effect of central 13-endorphin. In:
10.
11.
12. 13.
14.
15.
16.
17.
Lomax, P.; Schonbaum, E., eds. Environment, drugs and thermoregulation. Basel: S. Karger; 1983:104-107. McDougal, J. N.; Marques, P. R.; Burke, T. F. Reduced tolerance to morphine thermoregulatory effects in senescent rats. Life Sci. 28(2): 137-145; 1981. Mazzocchi, G.; Malendowicz, L. K.; Gottardo, G.; Nussdorfer, G. G. Evidence that prolonged et-MSH infusion enhances the steroidogesic capacity of rat adrenal zona glomerulosa in vivo. J. Steroid Biochem. 29(4):441-442; 1988. Murphy, M. T.; Lipton, J. M. Peripheral administration of ~t-MSH reduces fever in older and younger rabbits. Peptides 3:775-779; 1982. Murphy, M. T.; Richard, D. B.; Lipton, J. M. Antipyretic potency of centrally administered ct-melanocyte-stimulating hormone. Science 221:192-193; 1983. Robba,C.; Rebuffat, R.; Mazzocchi, G.; Nussadorfer, G. C. Longterm trophic action of tx-melanocyte-stimulating hormone on the zona glomerulosa of the rat adrenal cortex. Acta Endocrinol. 112:404---408; 1986. Samson, W. K.; Lipton, J. M.; Zimmer, J. A.; Glyn, J. R. The effect of fever on central ct-MSH concentration in the rabbit. Peptides 2:419-423; 1981. Tseng, L.; Loh, H. H.; Li, C. H. Human 13-endorphin: development of tolerance and behavioral activity in rats. Biochem. Biophys. Res. Commun. 74(2):390-396; 1977. Williams, D. W., Jr.; Lipton, J. M.; Giesecke, A. H., Jr. Influence of centrally administered peptides on ear withdrawal in the rabbit. Peptides 7:1095-1100; 1986.