buprenorphine and Tremor

Electrophysiological studies have demonstrated a physiological interaction between 5-HT2A and mu-opioid receptors in the medial prefrontal cortex. Furthermore, behavioral studies have found that phenethylamine hallucinogens induce head shakes when directly administered into the medial prefrontal cortex. The receptor(s) by which morphine suppresses head shakes induced by serotonin agonists have not been characterized. We administered mu-opioid receptor agonists and antagonists to adult male Sprague-Dawley rats prior to treatment with the phenethylamine hallucinogen 1-(2,5-dimethoxy-4-iodophenyl)-2-aminopropane (DOI), which is known to induce head shakes via 5-HT2A receptors. The suppressant action of the moderately selective mu-opioid receptor agonist, buprenorphine (ID50 approximately 0.005 mg/kg, i.p.; a mu-opioid receptor partial agonist and kappa-opioid receptor antagonist) was blocked by naloxone and pretreatment with the irreversible mu-opioid receptor antagonist clocinnamox. Another mu-opioid receptor agonist fentanyl also suppressed DOI-induced head shakes. In contrast, a delta-opioid receptor agonist was without effect on DOI-induced head shakes. Thus, activation of mu-opioid receptors can suppress head shakes induced by hallucinogenic drugs.

Topics: Amphetamines; Animals; Behavior, Animal; Binding, Competitive; Buprenorphine; Cinnamates; Male; Morphine Derivatives; Rats; Rats, Sprague-Dawley; Receptor, Serotonin, 5-HT2A; Receptors, Opioid, mu; Serotonin Receptor Agonists; Tremor

1. Doses of buprenorphine (0.01, 0.1, 0.5, 1, 5, 10 and 50 mg/kg) were administered to determine buprenorphine's ability to precipitate abstinence symptoms in morphine-dependent mice. 2. When buprenorphine was administered in the fourth day of morphine addiction, the results demonstrate that the administration of the partial agonist opioid produce a bell-shaped dose-response curve. 3. The highest dose (50 mg/kg) was partially inactive while lower doses causing similar percentage than group treated with naloxone with respect to the appearance of the most of the symptoms of abstinence studied (diarrhoea, tremor, shaking-"wet dog shakes"-, jumping and weight loss). 4. Our findings demonstrate the bell-shaped response curve of the antagonist effects of buprenorphine.

Topics: Animals; Behavior, Animal; Buprenorphine; Diarrhea; Dose-Response Relationship, Drug; Male; Mice; Mice, Inbred Strains; Morphine Dependence; Naloxone; Substance Withdrawal Syndrome; Tremor