An aspect of the organizational principle of the gamma-aminobutyric acidergic system in the cerebral cortex.

The possibility of the colocalization of a Ca2+-binding protein, parvalbumin (PV), with peptides, cholecystokinin (CCK) and somatostatin (SS), all of which are known to be contained gamma-aminobutyric acidergic neurons in the cerebral cortex, was tested in the rat visual cortex by means of immunohistochemistry using the adjacent section technique. No PV immunoreactive (PV-I) neurons showed CCK-like immunoreactivity, and almost none (932 out of 934 PV-I neurons examined) showed SS-like immunoreactivity. These observations suggest that the GABAergic system of the cerebral cortex may consist of some distinct subsystems with different chemical and presumably physiological characteristics.