Preliminary observations on the neuromelanic pigment in the substantia nigra nucleus of the cat.

The AA. study the behaviour of neuromelanic pigment in the substantia nigra of cats' mesencephalon. To this aim they suppress a first group of animals with MgSO4; a second group with a substance whose action is narcotic and curare-like. They carry out the observations on mesencephalon microtomic sections, some stained with hematoxylin, some treated with PAS reaction and some with Sudan Black. The results are: 1)- in the perikaryon of substantia nigra pars compacta neurons of cats suppressed with MgSO4, the pigment, absent in the early age of life, appears in adult age. It is characterized by brownish-yellow granulations, either scattered or clustered together. This finding is substantially similar to that observed in dogs' substantia nigra. 2)- The substantia nigra neurons of the mesencephalon taken from cats suppressed with a curare-like substance, appear instead, almost wholly, without the peculiar neuromelanic granulations. However intracytoplasmic bodies stained with hematoxylin and PAS positive, can be observed. In order to establish the morphological and histochemical events which occur in the substantia nigra neurons in depigmentation induced in this way the AA. consider further investigations absolutely necessary.