Cholera toxin effects on body temperature changes induced by morphine.

Abstract

The present study evaluates the influence of cholera toxin and its B-subunit on thermic responses to morphine in the rats. The holotoxin (1 microg/rat) and the B-subunit (5 microg) were administered ICV and three days later rats were challenged ICV with morphine and tested for changes of body temperature. Cholera toxin, but not its B-subunit, modified the time course of the hyperthermic response induced by a low dose of morphine (2.5 microg), converted the hypothermia due to a higher dose of morphine (18 microg) to a consistent hyperthermia and only partially reduced the greater hypothermia induced by 36 microg of morphine. Cholera toxin-induced modifications of thermic responses to morphine were paralleled with a decreased Gs(alpha) immunoreactivity and a reduced ability for the toxin to catalyse the "in vitro" ADP-ribosylation of Gs(alpha) in hypothalamic membranes. In contrast, at the same time when morphine-induced effects on body temperature were assessed, no changes in pertussis toxin-mediated ADP-ribosylation of Gi(alpha)/Go(alpha), or basal adenylate cyclase activity, or binding of mu-opioid receptor selective ligand [3H]-DAMGO were observed in hypothalamic areas from rats treated with cholera toxin. These findings suggest that adaptative events secondary to prolonged activation of Gs(alpha) play a role in the modifications of thermic responses to morphine induced by CTX.

• Authors: L Basilico, M Parenti, A Fumagalli, D Parolaro, G Giagnoni
• Journal: Pharmacology, biochemistry, and behavior (Pharmacol Biochem Behav) Vol. 56 Issue 3 Pg. 499-505 (Mar 1997) ISSN: 0091-3057 [Print] United States
• PMID: 9077589 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• Analgesics, Opioid
• Receptors, Opioid, mu
• Adenosine Diphosphate Ribose
• Morphine
• Cholera Toxin
• GTP-Binding Proteins
• Adenylyl Cyclases

Topics

• Adenosine Diphosphate Ribose (metabolism)
• Adenylyl Cyclases (drug effects)
• Analgesics, Opioid (pharmacology)
• Animals
• Body Temperature Regulation (drug effects)
• Catalysis
• Cholera Toxin (pharmacology)
• Drug Evaluation, Preclinical
• Female
• GTP-Binding Proteins (metabolism)
• Injections, Intraventricular
• Morphine (pharmacology)
• Rats
• Rats, Sprague-Dawley
• Receptors, Opioid, mu (drug effects)