Prenatal alcohol exposure in the second trimester-equivalent increases the seizure susceptibility in developing rats

We have previously reported that prenatal alcohol exposure (PAE) in the 2nd trimester-equivalent of gestation is associated with increased N-methyl-d-aspartate (NMDA)-induced generalized tonic-clonic seizures (GTCSs) prevalence in postpartum developing rats. Whether the 1st trimester-equivalent of gestation is also a vulnerable period for developing GTCSs following PAE is unknown. Here, we investigated the effects of a single episode of PAE at embryonic day 8 (E8, in the 1st trimester-equivalent) or E18 (in the 2nd trimester-equivalent) on NMDA-induced seizures in developing rats at postnatal day 7 (P7, the equivalent of preterm newborns) and P15 (the equivalent of term infants). Pregnant Sprague-Dawley rats were given a single oral dose of ethanol (5 g/kg body weight) at E8 or E18 and the postpartum rats were tested for the susceptibility to NMDA-induced seizures at either P7 or P15. NMDA-induced seizures consisted of wild running-like behavior (WRLB), flexion seizures (FSs), clonic seizures (CSs), GTCSs, and tonic seizures (TSs); these seizures were observed in both control-treated and PAE-treated, male and female, P7 and P15 rats. Quantification reveals that the overall prevalence of CSs, GTCSs and TSs occurrence were significantly increased in the E18-PAE group compared to E8-PAE group, adjusting for sex and postnatal day. Furthermore, the overall prevalence of FSs and TSs occurrence was significantly increased in PAE-treated males compared to females, adjusting for embryonic stage and postnatal day. The overall prevalence of WRLB and FSs occurrence was also increased in PAE-P7 rats compared to PAE-P15 rats, adjusting for sex and embryonic stage. We conclude that the susceptibility to develop GTCSs was higher when PAE occurred in the 2nd rather than in the 1st trimester-equivalent of gestation.