Our previous studies repeatedly demonstrated that prenatal
methamphetamine (MA) exposure alters seizure susceptibility in adult rats. Both the inhibitory
GABA system and the excitatory
NMDA system play a role in the effect of MA on epileptic
seizures. On the basis of our previous behavioral results, the effect of cross-fostering on seizure susceptibility in adult female rats was examined in the present study.
Bicuculline (
GABA(A) receptor antagonist) and
NMDA (
NMDA receptor agonist) were used to induce
seizures in adult female offspring exposed to MA in the prenatal and/or preweaning periods. Female dams were injected with MA (5mg/kg daily) or physiological saline (S) for approximately 9 weeks [about 3 weeks prior to impregnation, for the entire gestation period (22 days), and in the preweaning period (21 days)]. Absolute controls (C) did not receive any
injections. On postnatal day 1, pups were cross-fostered so that each mother received pups from all three treatments. Thus, nine groups (based on the prenatal and postnatal
drug exposures) of adult female rats were tested in each seizure test: C/C, C/S, C/MA, S/C, S/S, S/MA, MA/C, MA/S, MA/MA. The present study demonstrated that both the excitatory
NMDA system and the inhibitory
GABA system are involved in the proconvulsive effect of MA during prenatal and partially also postnatal development in female rats. However, because our results did not show any improvement in seizure susceptibility in prenatally MA-exposed animals that were fostered by control mothers (MA/C) relative to their siblings fostered by MA-treated mothers (MA/MA), our hypothesis of the cross-fostering effect seems to be incorrect in contrast to our behavioral studies.