Pharmacological analysis of hyperventilation in arthritic rats

The study examined the validity of increased minute volume of ventilation as a measurement of chronic pain in arthritic rats. The opiates morphine and R 62 818 attenuated arthritic hyperventilation, but only at doses which also reduced the ventilatory response to CO2 in normal rats. The non-steroidal anti-inflammatory drugs (NSAIDs), indomethacin and suprofen, the corticosteroids, cortisone and dexamethasone, and the tranquillizers, haloperidol and chlordiazepoxide, were essentially ineffective except at doses that also produced anti-inflammatory and/or toxic effects. A combination of an in itself ineffective dose of R 62 818 with an ineffective dose of suprofen did attenuate arthritic hyperventilation, and the combination constituted the only pharmacological treatment that did so in the absence of anti-inflammatory, toxic or intrinsic respiratory effects. The data are consistent with the hypothesis that pain rather than acidosis mediates arthritic hyperventilation. They also suggest that combinations of an opiate with an NSAID may perhaps be effective in alleviating this pain.