Altered neurochemical parameters in the brains of mice (Frings) susceptible to audiogenic seizures

In this study, several biochemical aspects of serotonergic neurons were compared in mice susceptible to audiogenic seizures (Frings) and in mice not susceptible to audiogenic seizures (CF 1). Tryptophan hydroxylase (TPH) activity was significantly lower in brains of Frings mice compared to CF1 mice; however, brain levels of 5-HT were similar in both strains. The significantly lower TPH activity in Frings mice was due to the altered kinetic characteristics of TPH activity in this strain. TPH from Frings mice had a significantly lower apparent maximal velocity and a significantly higher affinity for the substrate, as indicated by a lower apparent Km for tryptophan. The uptake of tryptophan and accumulation of 5-HT (following pargyline) were similar in Frings and CF 1 mice. The levels of 5-HT in selected brain regions of Frings and CF 1 mice were also similar, but NE levels were higher in the cerebral cortex and DA levels were higher in the neostriatum of Frings mice. It is unclear at this point what role, if any, 5-HT plays in susceptibility to audiogenic seizures in brains of Frings mice.