Naloxone-reversible antinociceptive activity of cathinone, the active principle of khat, in the mouse and rat

The analgesic activity of cathinone, an amphetamine-like agent considered as the major active principle of khat, was studied on three different nociceptive models. In mice, cathinone increased the reaction time when the hot-plate test was used and significantly reduced the number of writhings caused by i.p. administration of acetic acid. In rats, cathinone prolonged the reaction time of the tail-flick test. Surprisingly, this effect appeared to have two maxima, the second lasting several days. α-methyl-p-thyrosine and diethyldithiocarbamate, which affect catecholamine synthesis, and the opiate antagonist naloxone were both able to prevent cathinone antinociceptive actions. These results suggest that besides catecholamines opioid neurotransmitters are involved in the analgesic effect of an amphetamine-like agent.