Morphology and neurochemistry of two striatal neuronal subtypes expressing the GABAA receptor α3-subunit in the rat

The morphological characteristics, distribution and neurochemical phenotype of striatal neuronal subtypes expressing the GABA(A) receptor alpha 3-subunit were investigated using immunocytochemical and immunofluorescent techniques with an antibody specific for this subunit. alpha 3-immunopositive neurons were infrequent in the rat striatum, but two morphologically different subtypes were observed: Cholinergic neurons, and a second cellular type that may correspond to neurogliaform neurons, although it may also be a novel subtype of striatal interneuron. To identify the second cellular subtype, co-localization of the GABA(A) receptor alpha 3-subunit with markers of different classes of striatal interneurons was studied using specific antibodies. It was found that there was a lack of co-localization between all interneuronal markers used in this study and the alpha 3-subunit. Although the alpha 3-subunit immunopositive neurons represent a small percentage of the total of striatal neuronal populations, they may play an important role in the regulation of the microcircuitry of the striatum. (C) 2000 Elsevier Science B.V. All rights reserved.