Striatonigral and pallidonigral pathways studied by a combination of retrograde horseradish peroxidase tracing and a pharmacohistochemical method for gamma-aminobutyric acid transaminase.
The pharmacohistochemical neuronal staining method for gamma-aminobutyric transaminase (GABA-T) combined with retrograde horseradish peroxidase (HRP) staining was used to define more precisely the descending striatonigral and pallidonigral pathways. Previous studies have established that GABA-T intensive cells in the basal ganglia and other structures correspond with reported glutamic acid decarboxylase (GAD)-containing cells and are therefore presumed to use GABA as their neurotransmitter. Following injection of HRP into the substantia nigra, many HRP-labeled cells were detected in the caudate-putamen and globus pallidus. Two separate groups of cells were doubly labeled for GABA-T and HRP and seemed to represent two distinct GABA-T-rich descending pathways to the substantia nigra. One component came from medium-sized cells in the lateral aspect of the globus pallidus. It represented a majority of all descending cells from that nucleus. The other came from the lateral aspect of the caudate-putamen and represented only a minority of descending cells from that structure. These data suggest that the majority of striatonigral fibers are non-GABA containing while the majority of pallidonigral fibers are GABA-containing. The precise location of the GABA-T intensive cells making up these two pathways helps to explain much confusing data in the literature on the source of descending GABA fibers to the substantia nigra.
D000612:4-Aminobutyrate Transaminase / Q000378:metabolism*; D000818:Animals; D003342:Corpus Striatum / Q000033:anatomy & histology* / Q000201:enzymology; D005917:Globus Pallidus / Q000033:anatomy & histology / Q000201:enzymology; D005968:Glutamate Decarboxylase / Q000378:metabolism; D008297:Male; D009434:Neural Pathways / Q000033:anatomy & histology / Q000201:enzymology; D051381:Rats; D013378:Substantia Nigra / Q000033:anatomy & histology* / Q000201:enzymology
D000612:4-Aminobutyrate Transaminase; D005968:Glutamate Decarboxylase