Postnatal development of the GABA system in the rat spinal cord.

To assess the postnatal development of the GABA system in the rat spinal cord, GABA levels and GAD activity, as well as specific [3H]-muscimol binding, were determined in the dorsal and ventral areas. GABA levels and GAD activities did not vary in parallel from 1 to 8 postnatal days since the former decreased and the latter increased. After 8 days, however, increases in GABA levels and GAD activities were observed in tissues from the dorsal area and decreases were observed in tissues from the ventral area. Specific [3H]muscimol binding was unexpectedly high in both areas at 1 and 8 days but decreased linearly up to 22 days. Our findings show that there are distinct differences in the development of the GABA system in the rat spinal cord and brain.