title: Meloxicam selectively depresses the afterdischarge of rat spinal dorsal horn neurones in response to noxious stimulation.
abstract: This study examined the effects of the cyclooxygenase-2 (COX-2) inhibitor, meloxicam, on responses of spinal dorsal horn neurones to synaptic inputs in vivo. Experiments were run using male Sprague-Dawley rats (350-375 g) anesthetized with Na-pentobarbital (50 mg/kg, i.p.) and acutely spinalized at T9. Spinal segments L1-4 were exposed for extracellular single unit recording of on-going and stimulation-evoked activity of eight wide dynamic range neurones. On-going activity was unaffected by meloxicam (0.1 mg/kg, i.v.). However, responses to noxious mechanical stimulation (21 N for 3 s) of the cutaneous receptive field of the hind paw were depressed by meloxicam in particular the afterdischarge (34.50 +/- 6.06% inhibition) in all eight neurones studied. The brief initial discharge in response to stimulation was depressed less (15.31 +/- 4.89% inhibition, n = 7/8). The data indicate that the percent inhibition of the afterdischarge was significantly greater than that of the initial discharge (P < 0.05). Given the selectivity of meloxicam for COX-2, the data suggest that COX-2 may be involved in mediating and/or modulating excitatory effects of nociceptive inputs to dorsal horn neurones, in particular the prolonged stimulation-evoked afterdischarge.
authors.affiliation: Department of Physiology, McGill University, 3655 Sir William Osler, Montreal, H3G 1Y6, Quebec, Canada. graham.pitcher@utoronto.ca
authors.forename: G M
authors.initials: GM
authors.lastname: Pitcher
authors.forename: J L
authors.initials: JL
authors.lastname: Henry
mesh_terms: D018712:Analgesics, Non-Narcotic / Q000494:pharmacology*; D000818:Animals; D008297:Male; D000077239:Meloxicam; D009474:Neurons / Q000187:drug effects / Q000502:physiology*; D010146:Pain / Q000473:pathology / Q000503:physiopathology*; D010812:Physical Stimulation; D051381:Rats; D017207:Rats, Sprague-Dawley; D013116:Spinal Cord / Q000187:drug effects / Q000473:pathology / Q000503:physiopathology*; D013843:Thiazines / Q000494:pharmacology*; D013844:Thiazoles / Q000494:pharmacology*
chemical_list: D018712:Analgesics, Non-Narcotic; D013843:Thiazines; D013844:Thiazoles; D000077239:Meloxicam