Developmental changes in the expression of GABA(A) receptor subunits ((alpha(1),alpha(2),alpha(3)) in the cat visual cortex and the effects of dark rearing

The present study used Western blots and Northern slot blots to determine c hanges in the level of expression of GABA(A) receptor subunits alpha (1), a lpha (2), and alpha (3), in relation to the 'critical period' in cat visual cortex. Levels of the GABA(A) alpha (1) subunit were lowest at 1 week, inc reased four-fold to a maximum at 10 weeks, and declined slightly (35%) into adulthood. Levels of the GABA(A) alpha (2) and alpha (3) subunits were hig hest at 1 week of age, decreased two-fold by 10 weeks of age and were const ant thereafter. Comparison between visual cortex from normal and dark-reare d cats at 5 weeks and 20 weeks showed that alpha (1) and alpha (3) subunit expression was elevated in dark-reared animals by approximately 50% at both ages. alpha (2) expression was not affected. These results implicate the i mportance of a shift from putative immature to mature GABA(A) receptor subu nits during the critical period of visual cortex and in conjunction with pa rallel analysis of NMDA receptor subunit maturation, further support the no tion that a changing excitatory/inhibitory balance is critical for neuronal plasticity. (C) 2001 Elsevier Science BN. All rights reserved.