Reduced uptake and release of 5-hydroxytryptamine and taurine in the cerebral cortex of epileptic El mice.

Inbred mutant El mice are highly susceptible to convulsive seizures upon 'throwing' stimulation, and the inhibition of 5-hydroxytryptamine (5-HT) and taurine activities appears to be involved in the El mouse seizures. Uptake and release of [3H]5-HT and [3H]taurine into and from cerebral neurocortical slices using a superfusion system were investigated in both non-stimulated and stimulated El mice [El(-), El(+)] and in ddY mice, which do not have a convulsive disposition. Release was defined as 40 mM K+-stimulated release. 5-HT and taurine uptake in El(+) was lower than El(-) but no difference in either uptake was found between ddY and El(-). Release of 5-HT and taurine in El(-) was higher than in ddY whereas their release in El(+) was lower than in El(-). The taurine level in the cerebral neocortex of El(-) and El(+) was higher than in ddY. These results suggest that the synaptic function of the 5-HT and taurine containing neurons is suppressed and that dysfunction of these inhibitory neurons is involved in the seizure susceptibility in the El mice.