POSTNATAL ONTOGENY OF GABA(A) AND BENZODIAZEPINE RECEPTORS IN INDIVIDUAL LAYERS OF RAT VISUAL-CORTEX AND THE EFFECT OF VISUAL DEPRIVATION

The postnatal development of GABA(A) and benzodiazepine receptors was studied in the rat visual cortex with [H-3]muscimol and [H-3]flunitrazepam, respectively. The studies were performed by quantitative receptor autoradiography in the different cortical layers from normally raised rats and from monocularly deprived animals. In all cortical layers of normal rats there was a sharp (approx 3-fold) increase in [H-3]muscimol binding from days 1 to 10. Between postnatal days 10 and 20 there was a considerable decrease in GABA(A) receptors; thereafter this decline continued until adulthood but at a more moderate rate. In all cortical layers, [H-3]flunitrazepam binding increased sharply, also from day 1 to 10; at this age the adult values were practically attained. Monocular deprivation, by unilateral eyelid suture at the age of 11 days onwards lead to an increase in [H-3]muscimol binding in cortical layers IV-VI. This increase in GABA(A) receptors was detectable at the age of 25 days onwards. In contrast, monocular deprivation did not alter the density of benzodiazepine receptors in any of the cortical layers, and this lack of effects was regardless of the duration of visual deprivation. The present results suggest that the development of GABA(A) receptors in the deeper cortical layers, but not that of benzodiazepine receptors, is seemingly regulated by the visual experience at a critical period of brain maturation.