Effects of treatment with GABA(A) receptor subunit antisense oligodeoxynucleotides on GABA-stimulated Cl-36(-) influx in the rat cerebral cortex

GABAA receptor function was studied in cerebral cortical vesicles prepared from rats after intracerebroventricular microinjections of antisense oligod eoxynucleotides (aODNs) for alpha 1, gamma 2, beta 1, beta 2 subunits. GABA A receptor alpha 1 subunit aODNs decreased al subunit mRNA by 59 +/- 10%. S pecific [H-3]GABA binding was decreased by alpha 1 or beta 2 subunit aODNs (to 63 +/- 3% and 64 +/- 9%, respectively) but not changed by gamma 2 subun it aODNs (94 +/- 5%). Specific [H-3]flunitrazepam binding was increased by alpha 1 or beta 2 subunit aODNs (122 +/- 8% and 126 +/- 11%, respectively) and decreased by gamma 2 subunit aODNs (50 +/- 13%). The "knockdown" of spe cific subunits of the GABA(A) receptor significantly influenced GABA-stimul ated Cl-36(-) influx. Injection of alpha 1 subunit aODNs decreased basal Cl -36(-) influx and the GABA E-max; enhanced GABA modulation by diazepam; and decreased antagonism of GABA activity by bicuculline. Injection of gamma 2 subunit aODNs increased the GABA E-max; reversed the modulatory efficacy o f diazepam from enhancement to inhibition of GABA-stimulation; and reduced the antagonist effect of bicuculline. Injection of beta 2 subunit aODNs red uced the effect of diazepam whereas treatment with beta 1 subunit aODNs had no effect on the drugs studied. Conclusions from our studies are: (1) alph a 1 subunits promote, beta 2 subunits maintain, and gamma 2 subunits suppre ss GABA stimulation of Cl-36(-) influx; (2) alpha 1 subunits suppress, wher eas beta 2, and gamma 2 subunits promote allosteric modulation by benzodiaz epines; (3) diazepam can act as an agonist or inverse agonist depending on the relative composition of the receptor subunits; and (4) the mixed compet itive/non-competitive effects of bicuculline result from activity at alpha 1 and gamma 2 subunits and the lack of activity at beta 1 and beta 2 subuni ts. (C) 1999 Elsevier Science Ltd. All rights reserved.