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Effects of dose on effector mechanisms in morphine-induced hyperthermia and poikilothermia


The effect of a variety of morphine doses on thermoregulatory effector systems was examined in ambient temperatures of 27.0° C and 4.0° C. Rats were given saline or morphine sulfate (5, 15, or 25 mg/kg); their core temperature, oxygen consumption, and activity were monitored for 4 or 6 h post-injection. The results suggest two distinct actions of morphine, possibly mediated by two opiate receptors. Low doses of morphine produce hyperthermia that is the result of a direct activation of activity and whole body heat production. High doses produce effects dependent on ambient temperature: hypermetabolism and hyperthermia in the 27.0° C environment; hypometabolism, vasodilation, and hypothermia in the 4.0° C environment. The findings suggest limitations in current set-point theories of morphine's thermic actions.

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  1. Adler MW, Geller EB, Rosow CE, Cochin J (1988) The opioid system and temperature regulation. Ann Rev Pharmacol Toxicol 28:429–449

  2. Clark WG (1979) Influence of opioids on central thermoregulatory mechanisms. Pharmacol Biochem Behav 10:609–613

  3. Cox B, Ary M, Chesarek W, Lomax P (1976) Morphine hyperthermia in the rat: An action on the central thermostats. Eur J Pharmacol 36:33–39

  4. Cox B, Lee T, Vale J (1979) Effects of morphine and related drugs on core temperature of two strains of rat. Eur J Pharmacol 54:27–36

  5. Eikelboom R, Stewart J (1979) Conditioned temperature effects using morphine as the unconditioned stimulus. Psychopharmacology 61:31–38

  6. Geller EB, Hawk C, Keinath SH, Tallarida RJ, Adler MW (1983) Subclasses of opioids based on body temperature change in rats: acute subcutaneous administration. J Pharm Exp Ther 225:391–398

  7. Jorenby DE, Keesey RE, Baker TB (1988) Characterization of morphine's excitatory effects. Behav Neurosc 102:975–985

  8. Keppel G (1982) Design and analysis 2nd ed, Prentice-Hall, Englewood Cliffs, New Jersey

  9. Lin MT (1982) An adrenergic link in the hypothalamic pathways which mediate morphine- and beta-endorphin-induced hyperthermia in the rat. Neuropharmacology 21:613–617

  10. Lynch TJ, Martinez RP, Furman MB, Geller EB, Adler MW (1987) A calorimetric analysis of body temperature changes produced in rats by morphine, methadone, and U50, 448H. In: Harris L (ed) NIDA Res Monogr 76. Government Printing Office, Washington, DC, p 82

  11. Martin WR (1968) A homeostatic and redundancy theory of tolerance to and dependence on narcotic analgesics. In: Wikler A (ed) The addictive states. Williams and Wilkins, Baltimore, pp 206–225

  12. McDougal JN, Marques PR, Burks TF (1983) Restraint alters the thermic response to morphine by postural interference. Pharmacol Biochem Behav 18:495–499

  13. Mucha RF, Kalant H, Kim C (1987) Tolerance to hyperthermia produced by morphine in the rat. Psychopharmacology 92:452–458

  14. Numan R, Lal H (1981) Effect of morphine on rectal temperature after acute and chronic treatment in the rat. Prog Neuropsychopharmacol 5:363–371

  15. Paolino RM, Bernard BK (1968) Environmental temperature effects on the thermoregulatory response to systemic and hypothalamic administration of morphine. Life Sci 7:857–863

  16. Powell-Jones K, Saunders WS, St Onge RD, Thornhill JA (1987) Skeletal muscle thermogenesis: its role in the hyperthermia of conscious rats given morphine or beta-endorphin. J Pharmacol Exp Ther 243:322–332

  17. Vezina P, Stewart J (1985) Hyperthermia induced by morphine administration to the VTA of the rat brain, an effect dissociable from morphine-induced reward and hyperactivity. Life Sci 36:1095–1105

  18. Zelman DC, Tiffany ST, Baker TB (1985) Influence of stress on morphine-induced hyperthermia: relevance to drug conditioning and tolerance development. Behav Neurosci 1:122–144

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Correspondence to Timothy B. Baker.

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Jorenby, D.E., Keesey, R.E. & Baker, T.B. Effects of dose on effector mechanisms in morphine-induced hyperthermia and poikilothermia. Psychopharmacology 98, 269–274 (1989).

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Key words

  • Morphine
  • Hyperthermia
  • Set-point
  • Oxygen consumption
  • Thermoregulation