REGIONAL DIFFERENCES IN THE CRITICAL PERIOD NEURODEVELOPMENT IN THE MOUSE - IMPLICATIONS FOR NEONATAL SEIZURES

The voltage-sensitive calcium channel probe I-125-omega-GVIA conotoxin has been shown to be a developmental marker in whole brain preparatio ns of Swiss Webster mice. The present study looks more carefully at re gional dissections of the mouse brain (cerebrum, cerebellum, and brain stem) at postnatal day 8 and postnatal day 16. I-125-omega-GVIA. cono toxin binding, thought to be presynaptic, showed a dramatic increase b etween postnatal days 8 and 16 in the cerebral cortex, a decrease in t he cerebellum, and no change in the brain stem. The dramatic cerebral cortex increases indicated by these binding data correspond to a criti cal period between postnatal day 11 and postnatal day 14 in Swiss Webs ter mice; during this critical period, dendrites exhibit rapid outgrow th, sensory modalities come on line, electroencephalographic patterns mature, and the cortex reaches adult proportions. This period parallel s a similar initiation of electrical maturation in the 28- to 32-week neonatal human brain. We conclude from these data that the unusual cli nical presentation of neonatal seizures is not just the result of imma ture myelin formation. It includes incomplete synapse formation linkin g the cortex to the brain stem.