Cell loss and class distribution of TH-I cells in the substantia nigra of the neurological mutant, weaver.

Eight-week-old homozygous weaver mutant mice and littermate wildtype controls were perfused with a buffered acrolein and paraformaldehyde solution. The brains were subsequently removed, blocked and sectioned on a vibratome. Representative sections through the midbrain were incubated overnight with an antibody for tyrosine hydroxylase. Visualization of the antibody was achieved using the peroxidase-antiperoxidase technique. The immunoreactive cells in the substantia nigra were examined to determine the subclasses of cells that are affected when dopaminergic neurons are lost in these mutants. Class distributions were determined and the data were subjected to chi 2 analyses. The results indicate a significant loss of tyrosine hydroxylase-immunoreactive cells in both the pars compacta and pars lateralis that is dependent upon the group and the region being studied. In addition, distributional shifts within the classes of labeled neurons suggest that there is an increase in the small neurons over the expected numbers in both divisions of the substantia nigra.