Inhibition of ganglionic transmission by narcotic analgesics; an effect antagonized by naloxone, nalorphine and calcium.

Methadone, azidomorphine, oxycodone and fentanyl inhibit synaptic transmission in isolated sympathetic ganglia of the frog and rat, just as did morphine and pethidine in our previous investigations. This inhibitory effect can be antagonized not only by naloxone and nalorphine but also by increasing calcium concentration of the perfusion fluid of the ganglia. The inhibitory effect on transmission of narcotic analgesics takes place on specific opiate receptors of the peripheral ganglia.