TIME COURSE OF ALTERED SENSITIVITY TO FLUROTHYL FOLLOWING CORTICAL ABLATIONS IN RATS

¹ Department of Pharmacology, Temple University School of Medicine,Philadelphia, Pennsylvania

The present experiment was designed to determine the time course of altered sensitivity to flurothyl, a convulsant agent,following cortical ablations. Bilateral frontal cortical or posterior cortical ablations or a sham operation were carried out in 70 rats. Flurothyl was administered to single animals by inhalation as a 10% solution in 95% ethanol infused at a constant rate into a closed jar. Testing was carried out at 1, 4 and 8 weeks postoperatively. Two endpoints were employed; the time necessary to induce preclonic or myoclonic jerks, and the time necessary to induce aclonic convulsion with loss of posture. Animals with frontal ablations had a decreased sensitivity to flurothyl 1 week postoperatively, which gradually reversed to an increased sensitivity.This reversal occurred between 1 and 4 weeks postoperatively for the preclonic endpoint, and between 4 and 8 weeks for the convulsive threshold. Posterior ablations resulted in a similarpicture, but the reversal for both endpoints occurred between 1 and 4 weeks postoperatively.The results of the present study support the concept of denervation supersensitivity in the central nervous system.