title: On the mechanism of potentiation by morphine of thiopental sleeping time.
abstract: Injection of thiopental sodium, 25 or 40 mg/kg, i.p., into normal rats produced a prompt sleep which lasted 8.3 plus or minus 2.9 and 16.8 plus or minus 2.7 min, respectively. Injection of morphine sulphage, 20 mg/kg, i.p., itself produced only mild sedation but prolonged the thiopental induced sleep to 50 and 67.3 min, respectively. At 1 min after onset of sleep the brain thiopental concentration in morphine pretreated animals was significantly lower than in control animals. Furthermore the latter also awoke with higher brain thiopental concentrations; the morphine pretreated animals slept for a longer time despite lower brain thiopental concentration. The t1/2 of brain thiopental was longer in the morphine pretreated animals, 25 min, than in the control animals, 9 min. Distribution of thiopental in several tissues at various time periods following injection of thiopental revealed some time-related quantitative differences between the two groups but a similar qualitative pattern. It is suggested that morphine lowers the brain threshold for thiopental induced sleep.
mesh_terms: D000273:Adipose Tissue / Q000378:metabolism; D000818:Animals; D001798:Blood Proteins / Q000378:metabolism; D001921:Brain / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004347:Drug Interactions; D008297:Male; D009020:Morphine / Q000008:administration & dosage / Q000494:pharmacology*; D009132:Muscles / Q000378:metabolism; D011485:Protein Binding; D051381:Rats; D012890:Sleep / Q000187:drug effects*; D013874:Thiopental / Q000008:administration & dosage / Q000378:metabolism / Q000494:pharmacology*; D013997:Time Factors
chemical_list: D001798:Blood Proteins; D009020:Morphine; D013874:Thiopental