The understanding and treatment of pathological anxiety have long been a prime concern in regard to mental health. Alterations in GABAA function from controls are known to occur in anxiety disorders,6 including panic disorder, epilepsy,7 hypersensitive behavior,7b phobias,6 schizophrenia,8 alcoholism,9 Anglemans syndrome,7b and Rhetts syndrome,10 as well as effects which lead to/or complicate drug abuse.11 The 1,4-benzodiazepines, employed to treat anxiety disorders as well as sleep disorders exhibit anxiolytic, anticonvulsant, muscle relaxant/ataxic and sedative-hypnotic effects.5-12 Despite the clinical effectiveness of these drugs there is a need for selective anxiolytics and anticonvulsants which are devoid of myorelaxant/ataxic and sedative-hypnotic effects.5 Since BzR (benzodiazepine receptor) ligands allosterically modulate this system,1-5 the design of BzR subtype selective ligands5,25 is one means to generate better therapeutic agents.5 The combination of ligand affinities, molecular modeling and CoMFA analysis has been employed to determine the similarities and differences between BzR subtypes.25,26 This approach has permitted the synthesis of the most alpha5beta2gamma2 subtype selective agonist 5a reported to date,29 as well as several potent alpha5 selective inverse agonists 1a and 2a (50-75 fold more selective).25,28 Moreover, BCCt 6a (a neutral antagonist)31,32 and 3PBC 7a have been shown to be selective for alpha1beta2gamma2 subtypes, the former t-butylester is the most alpha1 selective agent in vitro reported to date.31,32 The alpha4/alpha6 """"""""diazepam- insensitive"""""""" ligands 3a,b and 4a,b are again the most potent selective DI ligands reported to date. These ligands serve as lead compounds in the search for BzR subtype specific agents. Based on modeling, variation of the ligand substituents (chiral or achiral; polar or nonpolar) which occupy lipophilic pockets L1, L2, L3, or Ldi of the pharmacophore/receptor model will provide the desired subtype selectivity. The lead compounds are illustrated in Schemes I and II, while the target compounds are depicted in Schemes III-XI. The goal is to develop ligands that are > 150 times more selective for either alpha1,alpha5,alpha4, or alpha6 (later alpha2,alpha3) subtypes in order to determine which biological function is mediated by which subtype(s). Characterization of the pharmacology of BzR at the subtype level is crucial for understanding the physiological processes which underlie anxiety, including panic disorder,6 convulsions,7 sleep disorders and cognition,16 as well as the design of selective agents to treat these disease states with reduced abuse potential.
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