Paternal care paradoxically increases offspring seizure susceptibility in the El mouse model of epilepsy

The El mouse is a model of idiopathic epilepsy in which seizures emerge on Postnatal Days (PNDs) 80–90, although time to first seizure can be modified by experiential factors including handling during development and history of past seizures. This study tested the hypothesis that a significant increase in the amount of parental investment would impact seizure susceptibility in adult El offspring. The study used a single dam control, in which the litter was reared by a female biological parent, and a biparental experimental group, in which both biological parents reared the litter. Components of parental care and pup body weights were quantified on PNDs 2–21, and adult offspring were examined using a handling-induced seizure susceptibility (HISS) test on PNDs 80–90 to assess the long-term impact of alterations in the perinatal environment. As expected, presence of both parents did increase parental/pup contact time by 350% relative to single-mother parenting and also reduced body weight, an index of perinatal stressor exposure, in already underweight El offspring. Accordingly, HISS testing of adult El offspring revealed a deleterious effect of biparental rearing, which increased seizure incidence to 30% relative to 0% for the single dam condition. These results suggest that the presence of a second care provider in addition to the dam constitutes a form of stressor exposure in El pups and, as a consequence, reduces the time to first seizure in genetically susceptible offspring.