Abstracts

Corticosteroids are frequently administered during the third trimester of pregnancy. While a single course of corticosteroid therapy is without effects in the offspring, the data on the outcome of multiple prenatal courses of corticosteroid therapy is insufficient. Here we determined the effects of two prenatal exposures to betamethasone on the offspring in terms of seizure susceptibility and behavioral development.
Timed pregnant rats were injected with two doses of betamethasone (0.4 mg/kg ip) on day 15 of embryonic development. Offspring were subjected to simple motor and behavioral tests (horizontal bar, elevated plus maze) and tested for seizure susceptibility after kainic acid (KA) challenge. Behavioral tests were also repeated following the KA seizures.
There was no weight difference between prenatally betamethasone- and saline-exposed rats on postnatal day (PN) 15. There was no difference in seizure susceptibility to develop KA-induced (3.5 mg/kg) automatisms and status epilepticus on PN 15. In the horizontal bar walking on PN 15 prior to seizures betamethasone-exposed rats performed significantly better than prenatally saline-exposed controls. However, when retested after KA seizures on PN 20, the difference disappeared. Repeated testing in the elevated plus maze on PN 20-22 indicated that that the betamethasone-exposed rats spent more time in the open arms.
The data suggest that repeated prenatal repeated betamethasone may have beneficial effects on simple motor performance. In the presence of a second, postnatal, insult prenatal betamethasone exposure may have detrimental effects. Prenatal betamethasone exposure may impair the acquisition of the task in the elevated plus maze test in developing rats. Thus, the beneficial and adverse effects of repeated prenatal corticosteroid therapy on the developing brains should be further rigorously studied to provide additional insights on possible outcome in humans.
[Supported by: NS/HD-41366 from NINDS and Heffer Family Medical Foundation.]