A phylogenetic tree of GABA_A receptor subunits. Amino acid sequences of GABA_A receptor subunits from humans, mice, and zebrafish were used to create a phylogenetic tree. This phylogenetic tree detected the subfamilies of α, γ/ ε, β/ θ, δ/π, and ρ. H: human; M: mouse; Z: zebrafish.

Spatial expression of zebrafish GABA_A receptor subunits. Whole-mount in situ hybridization of 5 dpf zebrafish larvae using antisense probes for gabra1 (a), gabra2a (b), gabra3 (c), gabra4 (d), gabra5 (e), gabra6a (f), gabra6b (g), gabrb1 (h), gabrb2 (i), gabrb3 (j), gabrb4 (k), gabrg1 (l), gabrg2 (m), gabrg3 (n), gabrd (o), gabrp (p), gabrz (q), gabrr1 (r), gabrr2a (s), gabrr2b (t), gabrr3a (u), and gabrr3b (v). Negative control without probe showing no signals (w). Regions of the olfactory bulb, forebrain, midbrain, hindbrain, and eye are indicated in the image (x). Each labeling image is composed of a whole lateral view (left top), a whole dorsal view (right top), a magnified lateral view of the head region (left bottom), and a magnified dorsal view of the head region (right bottom). The scale bars in the whole and magnified views are 1 mm and 200 μm, respectively. OB: olfactory bulb; FB: forebrain; MB: midbrain; HB: hindbrain.

Electrophysiological sensitivities of zebrafish GABA_A receptors to GABA. (a) Cumulative dose–response relationship of GABA-evoked currents recorded from Xenopus oocytes expressing the ρ2a subunit. (b) Cumulative dose–response relationship of GABA currents by the recombinant expression of the α subunit with the β3 subunit. (c) Cumulative dose–response relationship of GABA currents by the expression of the α subunit with the β3 and γ2 subunits. (d) Cumulative dose–response relationship of GABA currents by the expression of the β subunit with the α1 subunit. (e) Cumulative dose–response relationship of GABA currents by the expression of the β subunit with the α1 and γ2 subunits. (f) Cumulative dose–response relationship of GABA currents by the expression of γ or π subunits with α1 and β3 subunits. The amplitude of each GABA-evoked response was normalized to the maximally evoked current for each oocyte.