ABSTRACT
Young adult cats were subjected to unilateral ablation of the frontal and prefrontal cerebral cortex and were allowed to survive for 4 to 5 days. Routine electron microscopic technique was employed to examine orthograde degenerative changes in the ipsilateral and contralateral substantia nigra (Ni). A moderate number of degenerating synaptic boutons (d. s. b.) were observed in the ipsilateral Ni-pars comacta, and only very few d.s.b. were observed in the ipsilateral Ni-pars reticulata. The d. s. b. exhibited features attributed to the dark degeneration type, and might be referred to two main categories; "small-round-vesicle bouton" and "large-round-vesicle bouton" (Hajdu et al., 1973; Hassler et al. 1975). The d. s. b. performed asymmetrical synapses with dendrites of varying size, much more rarely -- with the neuronal perikarya, and extremely rarely -- with initial axonal segments. No degeneration was observed in the contralateral Ni.
Subject(s)
Frontal Lobe/anatomy & histology , Substantia Nigra/anatomy & histology , Animals , Axons/ultrastructure , Cats , Dendrites/ultrastructure , Dominance, Cerebral/physiology , Microscopy, Electron , Nerve Degeneration , Neural Pathways/anatomy & histology , Synapses/ultrastructureABSTRACT
Modifications of the selective silver impregnation methods of Nauta and Fink-Heimer are described. Both procedures were tested in wide variety of species: from reptiles to carnivores, as well as in human autoptic cases. The modified Nauta procedure is recommended as a method of choice for tracing axonal trajectories due to an improved impregnation selectivity of the degenerating axoplasm. Its use for the demonstration of monoaminergic (NA, DA, 5-HT) pathways, however, remains limited. The modified Fink-Heimer procedure demonstrates successfully the degeneration of axons, and especially--the thin preterminal arborizations, as well as the terminal boutons in many fiber systems studied, including the nigrostriatal, raphe-nigral, and coerulocortical tracts. Both methods provide an additional cytoarchitectonic orientation due to a counterstain of nerve cell bodies with cresylechtviolett.
