Abstract
The analgesic action of aminopyrine was studied by means of the hot-plate method with mice and by the electromyographic method with rabbits.
Aminopyrine in a dose of 0.5∼1.0 mg per 10 g was found to prolong the reaction time of mice to painful heat (at 55°C) stimuli. This analgesic effect of aminopyrine was depressed by the combination of sodium isomytal (sodium amytal) in a dose of 0.3 mg per 10 g, while the duration of the effect was prolonged by the combination of sodium isomytal in a dose of 0.1 mg per 10 g. The combined substance of aminopyrine, sodium isomytal and urethane in the weight ratio of 5: 1∼2: 10, was synergistic in the analgesic effect estimated by the hot-plate method.
By means of the electromyographic method, the nociceptively induced reflex activity of a rabbit's hindlimb was studied to reveal that aminopyrine facilitated the nociceptive reflex in a dose of 5∼30 mg per kg and inhibited in a dose of 40∼100 mg per kg. The inhibitory action of aminopyrine was produced more remarkably in intact rabbits than in spinal rabbits. However, the proprioceptively induced reflex activity in spinal rabbits was facilitated by aminopyrine in a dose of 5∼100 mg per kg.
From the above results, it is considered that the central analgesic action of aminopyrine might be produced by stimulation of the inhibitory center of brain and also by inhibition of spinal afferent synapses.
