Abstracts

Profound differences in seizure susceptibility in adult Fast and Slow kindling rat strains are associated with divergent behaviors in several paradigms. The distinct phenotypes of these strains have typically been attributed to genetic influence, yet a potential role for early life experience has not been excluded. Indeed, several conflicting behavioral phenotypes in rodents, similar to those in our strains, have been linked to maternal care in the post-natal period. Thus, maternal care may significantly impact strain-specific behaviors, including seizure predisposition. We examined maternal behavior and pup weights in the strains under 3 conditions: Control Fast and Slow pups raised by birth mother (FC and SC, respectively); Slow pups raised by a Fast mother (SPFM), and Fast pups raised by a Slow mother (FPSM); Slow pups raised by a different Slow mother (SPSM) and Fast pups raised by a different Fast mother (FPFM), i.e., controlling for the effects of fostering pups to a new mother, yet maintaining the same strain of dam. We then assessed seizure susceptibility in adult offspring using the amygdala kindling model. FC mothers exhibited higher frequencies of arched back nursing and [ldquo]with pup[rdquo] behaviors but less blanket posture nursing and [ldquo]no contact[rdquo] behaviors than SC mothers. Some maternal behaviors proved malleable by pup condition indicating pups can dictate those behaviors. Crossfostering impacted weight gain and expected differences in adult strain kindling profiles. Importantly, crossfostering alone influenced measures associated with epileptogenesis making both strains more [quot]Fast-like[quot] than controls. Also, compared to SC rats, crossing Slow rats to either maternal strain reduced the number of stimulations necessary to elicit an afterdischarge (AD) from the contralateral amygdala during primary site stimulation indicating greater seizure spread. FC and crossfostered rats from both strains exhibited AD durations in the contralateral amygdala that were nearly identical to those in the primary site on the first stimulation yet SC rats required approximately 8 stimulations to elicit similar AD durations in both amygdalae. Interestingly, the Slow maternal environment increased resistance to kindling in Fast pups such that kindling rates and cumulative afterdischarge durations to the first stage 5 seizure were indistinguishable from crossed Slow pup groups (SPSM and SPFM) but significantly longer than the FPFM group. Thus, several maternal behaviors differ between the strains. Importantly, however, while crossfostering alone made pups from both strains more seizure-prone it did not disrupt basic strain differences, except in the FPSM group. Clearly, the [apos]stress[apos] of crossfostering significantly affected several aspects of seizure predisposition yet the Slow maternal environment minimized those effects in Fast pups. (Supported by CHIR to DCM.)