The Differential Expression Pattern of the mRNAs Encoding β Subunits (β ₁ , β ₂ and β ₃) of GABA_A Receptor in Rat Brain

Abstract

Gamma-aminobutyric acid (GABA) is a well known major inhibitory neurotransmitter in the vertebrate brain. Its inhibitory action is mediated through the activation of the specific receptors: the GABA_A and GABA_B receptors. Binding of GABA with GABA_A receptor (GABA_A-R) causes the chloride channel to open (for reviews see Roberts, 1986; Stephenson, 1988). Recent molecular cloning analysis has revealed that GABA_A-R in the brain has at least five subunits and each subunit is consisted of several variants: α _1–5, β 1–3, γ 1–2, δ, and ε (Schofield et al., 1987; Levi tan et al., 1988; Richards et al., 1989; Schofield, 1989; Shivers et al., 1989; Ymer et al., 1989a, b). On the other hand, there is much evidence suggesting the heterogeneity of GABA_A-R in the brain. For example, using specific oligonucleotide probes for α ₁, α ₂ or α ₃ subunit mRNAs, Wisden et al. (1988) have revealed that the neurons expressing α ₁ and α ₂ subunit mRNAs are most abundant in layers II–IV of the bovine frontal cortex, while those expressing α ₃ subunit mRNA are most abundant in layers V and VI. In addition, recent investigation by Ymer et al.