Depressant effects of suprofen, a new non-steroidal anti-inflammatory drug on thalamic evoked neuronal firing in arthritic rats.
The effects of suprofen, a new non-steroidal anti-inflammatory drug, (NSAID), the activity of which is mainly antinociceptive, were compared with those of aspirin (as a reference drug) in a study of spontaneous and evoked firing of thalamic neurons (nucleus lateralis and ventrobasalis) in rats rendered arthritic by injection of Freund's adjuvant into the paw. Suprofen (3.7 mg/kg, i.v.) induced a marked decrease in the firing evoked in arthritic rats by ankle mobilization. This effect, after a rapid onset, lasted on the average for 60 min. A similar effect was obtained with aspirin, but with 54 mg/kg (i.v.) (14 times more than suprofen). With increasing doses of suprofen, it was possible to obtain an increased long-lasting inhibition of the evoked activity, with a significant dose-effect linear regression. The possibility that there are both CNS and peripheral effects of suprofen is discussed in relation to the possible role of aspirin (the reference standard for NSAIDs) in enhancing presynaptic inhibition, thus reducing the effectiveness of incoming sensory stimuli.