EFFECT OF AGMATINE ON SPINAL NOCICEPTIVE REFLEXES - LACK OF INTERACTION WITH ALPHA(2)-ADRENOCEPTOR OR MU-OPIOID RECEPTOR MECHANISMS

Agmatine has been tested i.v. in alpha-chloralose anaesthetised rats f or its effects on spinal nociceptive reflexes evoked by mechanical and electrical stimuli. Agmatine did not affect reflexes until very high doses (200 mg/kg, i.v.) which also caused complex cardiovascular distu rbances. In spinally intact rats agmatine reduced reflexes; it was sli ghtly less potent when there was carrageenan-induced hind paw inflamma tion. The alpha(2)-adrenoceptor antagonist atipamezole (80 mu g/kg) di d not significantly affect these reductions. In spinalised animals, ag matine caused a generalised increase in background firing which in ani mals with a non-inflamed paw was significantly reduced after atipamezo le. There was no significant change in evoked responses once corrected for background activity. In all groups of animals agmatine, when admi nistered at various doses and times prior to the mu-opioid receptor ag onist fentanyl, had no effect on the ID50 of fentanyl. (C) 1997 Elsevi er Science B.V.