Ketoprofen: i.c.v. injection and electrophysiological aspects of antinociceptive effect

The direct action of ketoprofen on the CNS was investigated by electrophysiological techniques in rats made arthritic. Between the 10th and 16th days after the administration of the complete Freund's adjuvant the rats were anesthetized and the drug was injected directly into the cerebral ventricles. The changes in spontaneous and evoked firing of thalamic neurons were investigated. Ketroprofen very rapidly inhibited the nociceptive activity induced by ankle mobilization. The inhibitory effects were maximal at the doses of 20 and 40 micrograms within 5 min and spontaneous activity was also reduced. The time courses of the action of the increasing doses were also measured. In view of the site of injection, the doses and the very rapid start of the effects, the inhibition of spontaneous and evoked neuronal firing supports the view of a direct effect of this drug on the electrical behaviour of the neurons.