A COMPARISON OF SOME CENTRAL EFFECTS OF MORPHINE, MORPHINONE AND THEBAINE ON RATS AND MICE

¹ Department of Pharmacology and Experimental Therapeutics, University of California San Francisco Medical Center, San Francisco, California

A combination metabolism chamber and body plethysmograph was used to study the effects of morphinone and thebaine on the respiration and oxygen consumption of rats. Morphinone was found to decrease tidal volume, but at doses of 10 mg/kg and up respiratory rate was increased. Little effect was seen on oxygen consumption. Thebaine at 5 mg/kg decreased tidal volume but had no effect on rate of respiration or oxygen consumption. Morphine, morphinone and thebaine were studied in mice to determine their effects on pentylenetetrazol convulsions and on electroshock convulsions. Morphine had no effect on pentylenetetrazol convulsions at low doses but lowered the convulsive threshold at high doses. Morphinone raised the convulsive threshold for pentylenetetrazol at both low and high doses while thebaine lowered it. Morphine, morphinone and thebaine had no effect on electroshock convulsions.