Effect of agmatine on spinal nociceptive reflexes: lack of interaction with alpha2-adrenoceptor or mu-opioid receptor mechanisms.
Agmatine has been tested i.v. in alpha-chloralose anaesthetised rats for 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 disturbances. In spinally intact rats agmatine reduced reflexes; it was slightly less potent when there was carrageenan-induced hind paw inflammation. The alpha2-adrenoceptor antagonist atipamezole (80 microg/kg) did not significantly affect these reductions. In spinalised animals, agmatine caused a generalised increase in background firing which in animals with a non-inflamed paw was significantly reduced after atipamezole. There was no significant change in evoked responses once corrected for background activity. In all groups of animals agmatine, when administered at various doses and times prior to the mu-opioid receptor agonist fentanyl, had no effect on the ID50 of fentanyl.
Bradley
K J
KJ
Department of Physiology, School of Medical Sciences, University Walk, Bristol, UK.
Headley
P M
PM
D000317:Adrenergic alpha-Antagonists / Q000494:pharmacology; D000376:Agmatine / Q000494:pharmacology*; D000701:Analgesics, Opioid / Q000494:pharmacology; D000818:Animals; D001794:Blood Pressure / Q000187:drug effects; D004558:Electric Stimulation; D005283:Fentanyl / Q000494:pharmacology; D006614:Hindlimb / Q000294:innervation; D008297:Male; D009046:Motor Neurons / Q000187:drug effects; D018482:Muscle, Skeletal / Q000187:drug effects / Q000294:innervation; D009619:Nociceptors / Q000187:drug effects*; D010812:Physical Stimulation; D051381:Rats; D017208:Rats, Wistar; D018341:Receptors, Adrenergic, alpha-2 / Q000187:drug effects*; D017450:Receptors, Opioid, mu / Q000819:agonists / Q000187:drug effects*; D012018:Reflex / Q000187:drug effects*; D013116:Spinal Cord / Q000187:drug effects / Q000502:physiology*
D000317:Adrenergic alpha-Antagonists; D000701:Analgesics, Opioid; D018341:Receptors, Adrenergic, alpha-2; D017450:Receptors, Opioid, mu; D000376:Agmatine; D005283:Fentanyl