Types and distribution of glutamic acid decarboxylase (GAD)-immunoreactive neurons in mouse motor cortex

Neuronal structures in mouse motor cortex that contain γ-aminobutyric acid (GABA), were identified by an immunocytochemical method, using an antiserum to glutamic acid decarboxylase (GAD). GAD-positive cell bodies occurred in all layers of the motor cortex, but were more concentrated in layers III and VI. GAD-positive puncta, presumably axon terminals, were also distributed throughout the cortical layers; a high density of puncta occurred in layer III, whereas a somewhat lower density characterized layer VI. Based on the shapes of their somata and dendritic trees we concluded that all GAD-positive cells were of the non-pyramidal type.