Synthesis and Evaluation of Analogues of the Partial Agonist 6-(Propyloxy)-4-(methoxymethyl)-β-carboline-3-carboxylic Acid Ethyl Ester (6-PBC) and the Full Agonist 6-(Benzyloxy)-4-(methoxymethyl)-β- carboline-3-carboxylic Acid Ethyl Ester (Zk 93423) at Wild Type and Recombinant GABA_A Receptors

Citations Over TimeTop 10% of 1998 papers

Abstract

A pharmacophore and an alignment rule have previously been reported for BzR agonist ligands. The design and synthesis of 6-(propyloxy)-4-(methoxymethyl)-beta-carboline-3-carboxylic acid ethyl ester (6-PBC, 24, IC50 = 8.1 nM) was based on this pharmacophore. When evaluated in vivo this ligand exhibited anticonvulsant/anxiolytic activity but was devoid of the muscle relaxant/ataxic effects of "classical" 1,4-benzodiazepines (i.e., diazepam). Significantly, 6-PBC 24 also reversed diazepam-induced muscle relaxation in mice. The 3-substituted analogues 40-46 and 48 of 6-PBC 24 and Zk 93423 27(IC50 = 1 nM) were synthesized and evaluated in vitro to determine what affect these modifications would have on the binding affinity at recombinant BzR subtypes. With the exception of the 3-amino ligands 40 and 41, all the beta-carbolines were found to exhibit high binding affinity at BzR sites. The 3-propyl ether derivative 45 was also evaluated in vivo and found to be devoid of any proconvulsant or anticonvulsant activity at doses up to 40 mg/kg. The 6-(1-naphthylmethyloxy) and 6-octyloxy analogues 25, 26, 28, and 29 of 6-PBC 24 were synthesized to further evaluate the proposed alignment of agonists vs inverse agonists in the pharmacophore of the BzR. In addition, ligands 26 and 29 were designed to probe the dimensions of lipophilic pocket L3 at the agonist site. The activity of 29 was evaluated in vivo; however, this analogue elicited no pharmacological effects at doses up to 80 mg/kg. These and other related beta-carbolines were also examined in five recombinant GABAA receptor subtypes. Ligands 52-61 all exhibited moderate to high affinity at GABAA receptors containing alpha1 subunits. These ligands will be useful in further defining the pharmacophore at alpha1 beta3 gamma2 receptors.

Related Papers

• → Time-dependent reduction in the anticonvulsant effectiveness of diazepam against soman-induced seizures in guinea pigs(2010)74 cited
• → Crystal Structure and Subsequent Ligand Design of a Nonriboside Partial Agonist Bound to the Adenosine A_2A Receptor(2021)40 cited
• → Synthetic and computer assisted analysis of the pharmacophore for agonists at benzodiazepine receptors(1991)56 cited
• → Benzodiazepine antagonist Ro 15-1788 (flumazepil) attenuates the anticonvulsant activity of diazepam in epileptic fowl(1987)4 cited
• → Effect of the anticonvulsant denzimol on the disposition of diazepam in the rat(1986)2 cited