Characteristic of analgesia induced by noncatecholic phenylethylamines in mice.

Using hot plate method, analgesia induced by noncatecholic phenylethylamines, phenethylamine, phenylethanolamine and amphetamine, was inhibited by naloxone, reserpine, apomorphine and p-chlorophenylalanine, while potentiated by haloperidol. These results suggest that phenylethylamines induced analgesia involves central dopaminergic and serotonergic neurons and endogenous opioid peptides. The blockade of dopaminergic neurons enhanced and the inhibition of serotonergic neuron activity or the stimulation of dopaminergic neurons attenuated the phenylethylamines induced analgesia. Using rat hind paw pressing or tail flick test, analgesia induced by electroacupuncture in which Hoku points were electrically stimulated through stainless steel needles was enhanced by phenylethylamines, haloperidol while attenuated by naloxone, reserpine, apomorphine and p-chlorophenylalanine. Thus the analgegic characteristic of phenylethylamines closely resembles that of electroacupuncture.