Postnatal development of GABA(A) receptor beta(1), beta(2/3), and gamma(2)immunoreactivity in the rat retina

GABA (gamma-aminobutyric acid) is the major inhibitory neurotransmitter in the mammalian central nervous system and plays an important role in neurona l physiology during ontogenesis, The distribution of the beta(1)-, beta(2/3 )-, and gamma(2)-subunit of the GABA(A) receptor in the rat retina was stud ied during postnatal development using immunohistochemical methods. All sub units were found at birth. However, each subunit showed a unique staining p attern with a different local distribution. The immunoreactivity pattern ch anged during the time course of postnatal development for each of the prote ins investigated. A clustered distribution at presumptive synaptic sites as indicated by a punctate staining pattern of the inner plexiform layer was detected as early as the second day of postnatal development. However, diff use staining of presumptive extrasynaptic sites was found throughout develo pment. The typical adult layering of immunoreactivity into distinctive band s appeared later in development, characteristically in the second postnatal week. The results of the present study suggest that GABA(A) receptor expre ssion precedes the formation of functional synapses and changes along with cellular differentiation of the rat retina. Developmentally regulated chang es in GABA(A) receptor composition and distribution indicate possible funct ions for this receptor during retinal ontogeny, J. Neurosci, Res. 57:185-19 4, 1999, (C) 1999 Wiley-Liss, Inc.