Phenylbenzimidazole derivatives as ligands for GABA receptors

Details Phenylbenzimidazole derivatives as ligands for GABA receptors Phenylbenzimidazole derivatives as ligands for GABA receptors

1999-07-20

2000-06-06

Shah, Mukund J.

Drug, bio-affecting and body treating compositions

Designated organic active ingredient containing

Heterocyclic carbon compounds containing a hetero ring...

544116, 544119, 544370, 544139, 544 584, 544 62, 546199, 5483044, 514394, 514322, 514255, 5142282, C07D23506, C07D40110, C07D40310, A61K 31445, A61K 31415

Patent

active

060719095

DESCRIPTION:

BRIEF SUMMARY
The present invention relates to a class of substituted benzimidazole derivatives and to their use in therapy. More particularly, this invention is concerned with substituted 1-phenylbenzimidazole derivatives which are ligands for GABA.sub.A receptors and are therefore useful in the therapy of deleterious mental states.
Receptors for the major inhibitory neurotransmitter, gamma-aminobutyric acid (GABA), are divided into two main classes: (1) GABA.sub.A receptors, which are members of the ligand-gated ion channel superfamily; and (2) GABA.sub.B receptors, which may be members of the G-protein linked receptor superfamily. Since the first cDNAs encoding individual GABA.sub.A receptor subunits were cloned the number of known members of the mammalian family has grown to include at least six .alpha. subunits, four .beta. subunits, three .gamma. subunits, one .delta. subunit, one .epsilon. subunit and two .rho. subunits.
Although knowledge of the diversity of the GABA.sub.A receptor gene family represents a huge step forward in our understanding of this ligand-gated ion channel, insight into the extent of subtype diversity is still at an early stage. It has been indicated that an .alpha. subunit, a .beta. subunit and a .gamma. subunit constitute the minimum requirement for forming a fully functional GABA.sub.A receptor expressed by transiently transfecting cDNAs into cells. As indicated above, .delta., .epsilon. and .rho. subunits also exist, but are present only to a minor extent in GABA.sub.A receptor populations.
Studies of receptor size and visualisation by electron microscopy conclude that, like other members of the ligand-gated ion channel family, the native GABA.sub.A receptor exists in pentameric form. The selection of at least one .alpha., one .beta. and one .gamma. subunit from a repertoire of seventeen allows for the possible existence of more than 10,000 pentameric subunit combinations. Moreover, this calculation overlooks the additional permutations that would be possible if the arrangement of subunits around the ion channel had no constraints (i.e. there could be 120 possible variants for a receptor composed of five different subunits).
Receptor subtype assemblies which do exist include, amongst many others, .alpha.1.beta.2.gamma.2, .alpha.2.beta.2/3.gamma.2, .alpha.3.beta..gamma.2/3, .alpha.2.beta..gamma.1, .alpha.4.beta..delta., .alpha.5.beta.3.gamma.2/3, .alpha.6.beta..gamma.2 and .alpha.6.beta..delta.. Subtype assemblies containing an .alpha.1 subunit are present in most areas of the brain and are thought to account for over 40% of GABA.sub.A receptors in the rat. Subtype assemblies containing .alpha.2 and .alpha.3 subunits respectively are thought to account for about 25% and 17% of GABA.sub.A receptors in the rat. Subtype assemblies containing an .alpha.5 subunit are expressed predominantly in the hippocampus and cortex and are thought to represent about 4% of GABA.sub.A receptors in the rat.
A characteristic property of all known GABA.sub.A receptors is the presence of a number of modulatory sites, one of which is the benzodiazepine (BZ) binding site. The BZ binding site is the most explored of the GABA.sub.A receptor modulatory sites, and is the site through which anxiolytic drugs such as diazepam and temazepam exert their effect. Before the cloning of the GABA.sub.A receptor gene family, the benzodiazepine binding site was historically subdivided into two subtypes, BZ1 and BZ2, on the basis of radioligand binding studies. The BZ1 subtype has been shown to be pharmacologically equivalent to a GABA.sub.A receptor comprising the .alpha.1 subunit in combination with a .beta. subunit and .gamma.2. This is the most abundant GABA.sub.A receptor subtype, and is believed to represent almost half of all GABA.sub.A receptors in the brain.
Two other major populations are the .alpha.2.beta..gamma.2 and .alpha.3.beta..gamma.2/3 subtypes. Together these constitute approximately a further 35% of the total GABA.sub.A receptor repertoire. Pharmacologically this combination appears to be equivalent to the BZ2

REFERENCES:
patent: 5360809 (1994-11-01), Axelsson et al.
patent: 5466706 (1995-11-01), George et al.
patent: 5554630 (1996-09-01), Teuber et al.
patent: 5554632 (1996-09-01), Teuber et al.
Rose, Chapter 2 in Goodman and Gil's The Tharmacological Basis of Therapeutics, 8th Ed., Pergamon Press, p. 33-35, 1990.
Nagarajan et al. Condesed heterotricycles: Novel Transformation fo Dibenz[b,e][1,4]diazepinones to benzimdidazole derivatives under Vilsmeier-Haack reaction conditions, India J. of Chem., 14, 1-3, Jan. 1976.
CAS Printout for CA 2092211, Sep. 1993.
CAS Printout for EP 563001, Sep. 1993.
K.A. Wafford, et al., Mol. Pharmacol., 50: 670-678 (1996).
G.R. Dawson, et al., Psychopharmacology 121: 109-117 (1995).
Bayley, et al., J. Psychopharmacology 10: 206-213 (1996).
L.J. Bristow, et al., J. Pharmacol. Exp. Ther. 279: 492-501 (1996).

Affiliated with

Also associated with

Rating

Phenylbenzimidazole derivatives as ligands for GABA receptors does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Phenylbenzimidazole derivatives as ligands for GABA receptors, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Phenylbenzimidazole derivatives as ligands for GABA receptors will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-2213763