[Stereological analysis of GABAergic neurons and calcium binding protein parvalbumin-containing neurons in the rat somatosensory cortex]

Abstract

The number of neuronal cells in the rat somatosensory cortex (barrel area) has been estimated by a stereological method, disector, using pairs of toluidine-blue stained plastic embedded 0.5 microns thick sections, 3.0 microns distant from each other. Chemical properties of those disector-counted cells were further revealed by applying postembedding immunocytochemical methods on adjacent semithin sections. Thus we analysed quantitatively the number, distribution and proportion of three types of neurons: 1) GABA negative neurons, 2) GABA-like immunoreactive (GABA-LIR) neurons and 3) a specific calcium binding protein parvalbumin (PV) immunoreactive (PV-IR) neurons, which are a subpopulation of GABA-LIR neurons. The densities of total neurons in the rat somatosensory cortex were 55 x 10(3)/mm3. Of neurons 24% and 12% were GABA-LIR and PV-IR, respectively; almost all PV-IR neurons are GABA-LIR and thus about 50% GABA-LIR neurons are PV positive. The number of total neurons under a unit surface area 1mm2 through the thickness of the somatosensory cortex is 85 x 10(3). GABA-LIR neurons were 20 x 10(3) and PV-IR neurons and PV negative GABA-LIR neurons were 10 x 10(3) and 10 x 10(3), respectively. The laminar distribution of each group of neurons shows prominent differences, indicating that the neuronal composition was different from layer to layer. The density of GABA-LIR neuron was highest in layer IV and especially PV-IR neurons were 2-3 times more numerous in layer IV than in layer II/III, V and VI.