The development of the extracellular space in neonatal rat inferior colliculus: An electron microscopic study,

Rat inferior colliculi were fixed by intracardiac perfusion of 4% methanol-free formalin in an isotonic phosphate-sucrose buffer, dehydrated in ethanol and studied during the first two weeks of postnatal life. The extracellular space during the first week was made up of intercellular gaps about 100–150 Å wide and large intercellular lakes (1–3 μ long) which diminished in size and number as maturation proceeded. Similar intercellular lakes were found in tissue fixed by immersion in glutaraldehyde containing ruthenium red. In these tissues an intense ruthenium red reaction product, distributed extracellularly, suggested an intercellular substance comparable to that described in adult brain. Intercellular lakes were also found in tissue dehydrated in acetone. Morphometric estimations indicated the extracellular space of neuropil during the first week to be about twice that of the adult, which was approached progressively.