Abstract
The effect of autonomic drugs on the analgesic action of morphine has been studied by many investigators. Some of them have attributed the analgesic properties of morphine, in part at least, to its adrenergic action, while the others to its cholinergic action.
In our laboratory Fujimura (1), using a modification of Hardy's radiant heat technique in man, has shown that the pain threshold elevating effect of morphine is potentiated by l-ephedrine or d-desoxymethylephedrine. Yanai (2) has tested the influence of autonomic drugs upon the pain reflex inhibitory action of morphine using the methods of D'Amour & Smith and Haffner, and reported that adrenaline, ephedrine, pilocarpine and methamphetamine potentiated the morphine action.
Ever since Fujita et al. (3, 4) introduced the electrophysiological technique into our laboratory, precise analysis on the sites of action of morphine has been made in cats.
In the present experiment, we have investigated the synergetic action of morphine with methamphetamine on several afferent pathways of the central nervous system by means of the electrophysiological method.
