Postnatal development of forebrain regions in the autoimmune NZB-mouse. A model for degeneration in neuronal systems.

NZB-mice are known to have impaired cognitive functions. The aim of the present study is the analysis of the volume growth of different brain regions in NZB/NBOM-mice, because the functional impairment increases postnatally. The regions analysed include brain structures which are important for learning and memory functions. The comparison between NZB-mice and controls (CFW- and Balb/c-mice) shows that the hippocampal volume in NZB-mice is larger than in controls. However, ectopic neurons are found in the dentate gyrus of NZB-mice, indicating a changed connectivity in this region. The septum and the amygdala show no difference in volume in NZB-mice compared to controls. The adult volume of the entorhinal cortex of the NZB-mice is the smallest of the three strains. The development of this brain region is characterized by an overshooting growth in all strains. The caudate-putamen complex and the globus pallidus of NZB-mice undergo a reduction in volume during the postnatal period. This is not found in the controls. An overshooting growth is seen in the mamillary bodies of the three strains, and in the anterior thalamic nucleus of NZB-mice. However, only the NZB-mice show a prolonged reduction of the volume of the mamillary bodies, which is not finished during the observed time period. Both regions are important relay stations in the Papez-circuit, a neuronal system associated with learning and memory functions. The prolonged postnatal reduction in volume of the mamillary bodies and the anterior thalamic nucleus of NZB-mice may be the structural correlate of the impaired cognition and memory in this strain.