Delayed postnatal behavioral development in spontaneously epileptic rats and tremor rats, and poor operant performance in spontaneously epileptic rats

Postnatal behavioral development and learning ability of operant performance were examined in spontaneously epileptic rats (SER: zi/zi, tm/tm), and the original tremorous mutant strains of rats, tremor rats (tm/tm) and zitter rats (zi/zi) and their controls. Before the eyes opened, the increase in body weight and the age of achieving the righting reflex on a surface were no significantly different between the SER and their littermates without epileptic seizures (SER-N: zi/zi, tm/+ or zi/zi, +/+), and between tremor rats and the original strain Kyo: Wistar rats. After the eyes opened, the increase in body weight, age of achieving the righting reflex in air and traction performance, and the development of rotarod performance, were delayed in SER and tremor rats in comparison with other groups of rats. The zitter rats were apparently inferior in their development of rotarod performance in comparison with the same zitter homozygous SER-N. Operant performance was more inferior in SER than in SER-N and in tremor rats than in Kyo: Wistar rats. The differences were much more marked between SER and SER-N than between tremor and Kyo: Wistar rats. Thus, homologous tm genes and the coexistence of homologous tm and zi genes have an inhibitory effect on postnatal behavioral development and learning ability.