Anticonvulsant enaminone E139 suppresses epileptiform activity in rat hippocampal slices

Some enaminones are reported to have in vivo anticonvulsant activity. We asked if methyl 4-(4'-bromophenyl)aminocyclohex-3-en-6-methyl-2-oxo-1-oate (E139), one of such enaminones produced in vitro effects that may underlie or explain these in vivo anticonvulsant actions by testing if E139 suppressed in vitro seizures. In vitro seizures were generated chemically in hippocampal slices using picrotoxin and zero Mg(2+) buffer and electrically by high frequency stimulation (HFS). E139 (10 microM) depressed evoked field population spike (PS) amplitude by -28.6+/-4.5% (n=5), an effect that was blocked by 1 microM CGP55845 (2.7+/-5.5%, n=6). Picrotoxin (100 microM) transformed single PS into multiple PS (4.5+/-0.2, n=5) and E139 reversibly reduced the number of these multiple PS by -23.4+/-1.8% (n=5). Similarly, zero Mg(2+) buffer produced multiple spikes (3.6+/-0.6, n=5) that were suppressed by E139 (-54.8+/-9.7%, n=5). This effect was also blocked by CGP55845 (2.3+/-5.7%, n=6). Furthermore, E139 suppressed the frequency of spontaneous bursts (SB) that were recorded in zero Mg(2+) by -65.8+/-10.5% (n=12). CGP55845 significantly reduced this E139-induced SB suppression (-21.7+/-9.6%, n=6). In the electrical model, afterdischarges (AD) and SB recorded in area CA3 after a pattern of HFS (100Hz) were suppressed by E139 (-48.6+/-14.3% and -66.7+/-6.7%, respectively, n=6). These E139 effects on AD and SB were reduced, but not completely blocked, by CGP55845 (-32.1+/-5.3% and -44.4+/-9.7%, respectively, n=7). Finally, pretreatment of slices with E139 did not prevent zero Mg(2+)-induced multiple spikes and SB. We conclude that E139 suppresses in vitro seizures in the hippocampus by synaptic and non-synaptic mechanisms. These actions on network activity may underlie their reported in vivo anticonvulsant effects.