1.A.9.5.6
Gamma-aminobutyric acid receptor, LCCH3 (β) of 496 aas and 4 TMSs/ GRD of 686 aas and 4 TMSs.  LCCH3 combines with the ligand-gated ion channel subunit, GRD, to form cation-selective GABA-gated ion channels.  The heteromultimeric receptor is activated by GABA (EC50=4.5 microm), muscimol (EC50=4.8 microm) and trans-4-aminocrotonic acid (EC50=104.5 microm), and partially by cis-4-aminocrotonic acid (EC50=106.3 microm). Picrotoxin effectively blocked the GABA-gated channel (IC50=0.25 microm), but bicuculline, TPMTA, dieldrin and lindane did not. The benzodiazepines flunitrazepam and diazepam did not potentiate the GABA-evoked current (Gisselmann et al. 2004). The system has been partially characterized from the small brown planthopper, Laodelphax striatellus (Fallen), a major insect pest of crop systems in East Asia (Wei et al. 2017). Isocycloseram is a "GABA-gated chloride channel allosteric modulator (Blythe et al. 2022). A GABA-gated chloride channel mutation (Rdl) induces cholinergic physiological compensation resulting in cross resistance in Drosophila melanogaster (Xie et al. 2024).