The influence of clonidine on the naloxone-induced withdrawal signs, escape attempts and precipitated shakes, was studied in morphine-dependent rats. Clonidine injected i.p. or intraventricularly (i. vent.) inhibited precipitated shakes and potentiated escape attempts induced by naloxone in morphine-dependent rats. Under pentobarbital anesthesia, precipitated shakes and ice water-induced wet shakes were inhibited by clonidine and norepinephrine. Clonidine injected i.vent. reduced body temperatures in morphine-implanted rats and in placebo pellet-implanted rats. Naloxone reduced body temperatures only in morphine-dependent rats but not in placebo pellet-implanted rats. We suggest that clonidine modulates morphine withdrawal signs by potentiating the behavior associated with heat dissipation (escape attempts) and inhibiting the behavior associated with heat gain mechanisms (precipitated shakes). These effects may occur via stimulation of central noradrenergic mechanisms.
Bibliographical noteFunding Information:
This work was supported by Grants DA 00091 and DA 00564 from the National Institutes of Health. We are grateful for the generous supply of clonidine from Boehringer Ingel-helm and of naloxone • HC1 from Endo Laboratories. The authors also gratefully acknowledge the excellent technical assistance of Ms. Sheelah Sigel and Mr. J.B. Cunningham and the assistance of Barbara Halperin in preparation of the manuscript.
- Morphine abstinence signs
- Thermoregulatory behavior