Microinfusion of
anticonvulsants into the perirhinal cortex through 1 guide
cannula in each hemisphere only invades a small area of this seizure controlling site in rats exposed to
soman. The purpose of the present study was to examine whether infusions made through 2 cannulas in each perirhinal cortex may produce more efficacious
anticonvulsant action against
soman intoxication than the use of 1
cannula only in rats infused with the ionotropic antagonists
procyclidine and
caramiphen or the metabotropic
glutamate modulators
DCG-IV and MPEP. The results showed that the mere presence of indwelling double cannulas caused proconvulsant effect in response to subsequent systemic administration of
soman. Both the control and
caramiphen groups with double cannulas had significantly shorter latencies to seizure onset than the corresponding groups with single
cannula.
Procyclidine resulted in
anticonvulsant efficacy, even in rats with double cannulas. In rats that received twin infusions of
DCG-IV or MPEP, the
anticonvulsant impact was very high, inasmuch as a majority of the rats in each group was protected against seizure activity. Drugs possessing powerful
anticonvulsant potency can apparently counteract the proconvulsant effect of double cannulas, and some can even gain enhanced
anticonvulsant capacity when invading a larger area of the perirhinal cortex. Perirhinal EEG recordings (
electrodes in indwelling cannulas) in a separate set of rats not exposed to
soman or drugs showed no differences in basal electrical activity (total power 0.5-25Hz or the theta band 4-12Hz) between groups with single or double cannulas. The intrinsic excitability and synaptic connectivity of the perirhinal cortex may be associated with the proconvulsant impact observed in rats with double cannulas when exposed to
soman.