GAB.sub.A a receptor subtypes and methods for screening drug compounds using imidazoquinoxalines and pyrrolopyrimidines to bind to GABA.sub.a receptor subtypes

A method of screening compounds for potential therapeutic activity comprising;

• (a) adding flumazenil to a preparation containing GABAa receptors to allow the flumazenil to bind to GABAa receptors;
• (b) utilizing the resulting treated preparation from (a) in a reaction mixture for conducting a competition reaction between a compound of Formula (I) or (II) radiolabeled with tritium or an iodine isotope and the compound to be screened for remaining GABAa receptors, to which flumazenil has not bound but which have a specific binding site for a compound of formula I or II;
• (c) separating the GABAa receptor bound radiolabeled compound of formula I or II from the reaction mixture of (b);
• and
• (d) measuring the radioactivity resulting from specific binding of the radiolabeled compound of formula I or II to the remaining GABAa receptors,
• where formulae I and II are ##STR17## and the pharmaceutically acceptable salts thereof wherein:
• R.sub.1, R.sub.2, R.sub.3, R.sub.4 independently represent hydrogen, halogen, straight chain or branched lower alkyl having 1-6 carbon atoms, or straight chain or branched lower alkoxy having 1-6 carbon atoms;
• R.sub.5 is hydrogen or straight chain or branched lower alkyl having 1-6 carbon atoms;
• X and Y are the same or different and represent hydrogen, halogen, straight chain or branched lower alkyl having 1-6 carbon atoms, or straight chain or branched lower alkoxy having 1-6 carbon atoms;
• and
• Z is hydrogen or fluorine.