The striatal GABA-ergic neurons expressing substance P receptors in the basal ganglia of mice.

By using a double immunofluorescence, we have examined the distribution of striatal GABAergic neurons that expressed substance P receptor (SPR) in the basal ganglia of adult C57 mice. The distribution of GABA-immunoreactive neurons completely or partially overlapped with that of SPR-immunoreactive neurons in the striatum (i.e. the caudate-putamen), globus pallidus, ventral pallidum, and nucleus accumbens. Neurons showing both GABA- and SPR-immunoreactivities were, however, predominantly found in the caudate-putamen, and most of them were characterized by their large-sized aspiny neuronal profile. Semi-quantification indicated that only about 13% of the total GABA-immunoreactive neurons (including large and medium-sized) displayed SPR-immunoreactivity, and these double-labeled neurons constituted about 31% of the total SPR-immunoreactive cells in the striatum. Neurons double-labeled with GABA- and SPR-immunoreactivities were hardly detected in other aforementioned regions of the basal ganglia. In addition, double immunofluorescence also showed co-localization of SPR- with glutamic acid decarboxylase-immunoreactivity, but not with parvalbumin-immunoreactivity, in the striatal neurons. Taken together with previous reports, the present study has suggested that a sub-population of striatal GABA-ergic neurons, most possibly GABA-ergic interneurons, may also receive direct physiological modulation by tachykinins through SPR in the basal ganglia of mammals.