THE USE OF IN-VIVO ANTISENSE OLIGONUCLEOTIDE TECHNOLOGY FOR THE INVESTIGATION OF BRAIN GABA(A) RECEPTORS

Antisense oligodeoxynucleotides (ODN) can be used as selective inhibit ors of in vivo gene expression in the central nervous system (CNS) of experimental animals. The gamma-aminobutyric acid type A (GABA(A)) rec eptor is a member of the ligand-gated ion channel superfamily of neuro transmitter receptors. GABA(A) receptor function is allosterically mod ulated by several clinically important compounds, e.g. 1,4-benzodiazep ines, barbiturates and certain neurosteroids, which recognize binding sites within the receptor complex. GABA(A) receptor chloride channel c omplexes are probably pentamers of different polypeptide subunits. The number of known subunit families and isoforms (six alpha s, four beta s, three gamma s, one delta and two rho s) indicates an extensive het erogeneity of GABA(A) receptors. The gamma 2 subunit is a functionally integral part of the GABA(A) receptor, necessary for the high affinit y binding of benzodiazepines. The infusion of phosphorothioate ODN ant isense to the gamma 2 subunit mRNA, but not control sense or mismatch ODN, into the lateral cerebral ventricle or into the hippocampus of ra ts leads to significant decreases in benzodiazepine receptor radioliga nd binding. In the hippocampus this is accompanied by a decrease in th e number of GABA(A) receptors and by a loss of neurones, the latter po ssibly being due to reduced GABAergic inhibitory neurotransmission. Au toradiographic analysis following continuous intrahippocampal infusion of antisense ODN shows the regional extent of the effect on [H-3]flun itrazepam binding. The continuous infusion of antisense ODN, but not o f mismatch control ODN, into the right lateral cerebral ventricle indu ced a significant decrease in benzodiazepine binding and [H-3]muscimol binding to membranes of the right cortex. Antisense ODN infused into the striatum decreased benzodiazepine binding and binding to the GABA binding site of the GABA(A) receptor to an extent similar to that foun d in the hippocampus. It is concluded that the preferred route of admi nistration of antisense ODN for in vivo studies of the GABA(A) recepto r may be by infusion into defined rat brain regions. The reported data support the idea that antisense ODN can be used as a valuable tool fo r the investigation of the contribution of individual GABA(A) receptor subunits to the properties of the receptor complex and of mechanisms of receptor subunit assembly. (C) 1997 Elsevier Science Ltd.