Tissue culture analysis of neurogenesis: Myelination and synapse formation are retarded by serum deprivation

Explants from newborn mouse cerebellum were cultured in nutrient media containing either adequate (30%) or low (15% or 7.5%) serum content. By light microscopic observation, delayed and inhibited myelination was detected in cultures fed with low serum media (experimental cultures). Specific activities of two enzymes related to myelin synthesis, 2′,3′-cyclic nucleotide-3′-phosphohydrolase and 3-hydroxy-3-methylglutaryl coenzyme A reductase, were also reduced in experimental cultures. Morphometric analysis of electron micrographs showed that the size of presynaptic endings and total area occupied by synapses in experimental cultures were substantially reduced, while synaptic density per unit area increased. Reflecting the results of synaptic underdevelopment, the levels of two neurotransmitter enzymes, choline acetyltransferase and glutamic acid decarboxylase, were also decreased in experimental cultures.