Interaction of insecticides with heteromeric GABA-gated chloride channels from zebrafish Danio rerio (Hamilton)

摘要

The ionotropic GABA(A) receptor (GABA(A)R) is the main fast inhibitory post-synaptic receptor and is also an important insecticidal target. Effect of insecticides on fish has attracted intensive attention. However, no systematic study on heteromeric zebrafish GABAAR expressed in oocytes has been reported to date. In this study, the alpha 1 subunit, the beta 2S subunit lacking 47 amino acid residues compared with the beta 2L subunit, and the gamma 2 subunit having five transmembrane domains were isolated from zebrafish Danio rerio. The responses of homomeric and heteromeric (alpha 1, beta 2S and gamma 2) channels to agonists and GABA(A)R-targeted compounds were detected with two electrode voltage clamp. Dose-dependent responses were observed in heteromeric alpha 1 beta 2S, beta 2S gamma 2, and alpha 1 beta 2S gamma 2 GABAR channels with EC50 values at 21.75, 6291, and 33.69 mu M for GABA-induced current and 3.28, 155.5, and 3.79 mM for beta-alanine-induced current, respectively. However, no response was induced by benzamidine in all GABAR channels. Abamectin, dieldrin, fluralaner and fipronil could strongly inhibited GABA-induced inward current = 50% at 10(-6) M, while alpha-endosulfan, flufiprole and ethiprole only inhibited GABA-induced current 50%. This study has clarified the interaction of insecticides with the heteromeric GABA(A)R channel, which could help us further explore the potential function and toxicological importance of GABA(A)Rs from D. rerio.