Neuroanatomy of cerebellum and olfactory bulb in a substrain of C57BL/6J inbred mice carrying a spontaneous mutation.

Mice of the inbred C57BL/6JNmg substrain carry a mutation decreasing the size of the zinc-rich hippocampal intra- and infrapyramidal mossy fibre (IIPMF) terminal fields. In the present experiment, it was investigated whether this neurological mutation has also effects on other characteristics of the brain. No morphological differences were found in two other laminated neural structures, the olfactory bulb, where the accessory granular layer is also rich in zinc terminals, and the cerebellum. However, the mutants had a somewhat inferior performance on a motor function task known to test cerebellar involvement. The present findings confirm that previously found effects of this mutation on different types of behaviour are most probably due to the IIPMF. These substrains provide a powerful tool to localise the gene involved and subsequently investigate the plausible pathways leading from gene to behaviour.