Different mossy fiber patterns in two inbred strains of mice: a functional hypothesis

Quantitative and qualitative evaluations of the distribution of mossy fiber terminals in the hippocampal region inferior were performed in two inbred strains of mice, SECRe/J and C57BL/6, known to have different learning abilities. The results confirmed previous observations showing that there are fewer mossy fiber terminals along basal dendrites of the CA3 pyramidal cells in the high performer strain (SECRe/J). One additional, qualitative difference between the strains was found near the hilus and in particular at dorsal levels. Thus strands of mossy fiber terminals connecting the infra- and suprapyramidal mossy fiber layers were more significant and more randomly oriented in the C57BL/6 strain than in SECRe/J. In an otherwise laminar structure like the hippocampus this might have a similar functional importance as the quantitative differences.