Functional decortication employing reverberating cortical spreading depression: Experimental evaluation of advantages and limitations

Abstract

Possible use of reverberating cortical spreading depression for inducing functional decortication was studied in rats anesthetised with Allobarbital. In the chronic technique a thermocoagulation lesion 5 mm in diameter was made in the frontal cortex 3–13 days before the actual experiment. Appropriately spaced and timed microinjections of 1.3m KCl elicited 12.6 cycles of reverberating cortical spreading depression (n = 9) in the first week and 3.5 cycles (n = 11) in the second week after surgery. In order to avoid cortical injury functional obstacle (20-min treatment of cerebral cortex with 1.0 m MgCl₂ solution) was used instead of thermocoagulation in another series of experiments. With pharmacological facilitation by a pyrrolopyrimidine derivative BW 58-271 (10 mg/kg) it was possible to elicit 13.3 cycles of reverberating cortical spreading depression (n = 19). Amplitude of the slow potential change was high with the functional obstacle (9.7 mV) and low in the chronic preparation (2.0 mV). Functional decortication by reverberating cortical spreading depression decreases the amount of externally applied KCl but its practical use is limited by long cycle duration (5–6 min), obligatory electrophysiological control and presence of focal lesion (chronic techniques) or preservation of activity in the MgCl₂ treated area.