Biochemical, electrophysiological and neurohormonal studies with B-20991, a selective 5-HT1A receptor agonist

New serotonin 5-HT1A receptor agonists endowed with antinociceptive activity in vivo

We report the synthesis of new compounds 4-35 based on two different openings (A and B) of the chromane ring present in the previously identified 5-HT1A receptor (5-HT1AR) ligand 3. The synthesized compounds were assessed for binding affinity, selectivity, and functional activity at the 5-HT1AR. Selected candidates resulting from B opening were also evaluated for their potential antinociceptive effect in vivo and pharmacokinetic properties in vitro. Analogue 19 [2-(4-{[2-(2-ethoxyphenoxy)ethyl]amino}butyl)tetrahydro-1H-pyrrolo[1,2-c]imidazole-1,3(2H)-dione] has been characterized as a high-affinity and potent 5-HT1AR agonist (Ki = 2.3 nM; EC50 = 19 nM). Pharmacokinetic studies indicated that compound 19 displays a good metabolic stability in human liver microsomes (t1/2 ∼ 3 h and CLint = 3.5 mL/min/kg, at 5 μM), and a low level of protein binding (25%, at 5 μM). Interestingly, 19 (3 mg/kg, ip, and 30 mg/kg, po) caused significant attenuation of formalin-induced behavior in early and late phases of the mouse intradermal formalin test of pain, and this in vivo effect was reversed by the selective 5-HT1AR antagonist WAY-100635. Thus, the new 5-HT1AR agonist identified in this work, 19, exhibits oral analgesic activity, and the results herein represent a step toward identifying new therapeutics for the control of pain.

New serotonin 5-HT(1A) receptor agonists with neuroprotective effect against ischemic cell damage

We report the synthesis of new compounds 4-35 based on structural modifications of different moieties of previously described lead UCM-2550. The new nonpiperazine derivatives, representing second-generation agonists, were assessed for binding affinity, selectivity, and functional activity at the 5-HT(1A) receptor (5-HT(1A)R). Computational β(2)-based homology models of the ligand-receptor complexes were used to explain the observed structure-affinity relationships. Selected candidates were also evaluated for their potential in vitro and in vivo neuroprotective properties. Interestingly, compound 26 (2-{6-[(3,4-dihydro-2H-chromen-2-ylmethyl)amino]hexyl}tetrahydro-1H-pyrrolo[1,2-c]imidazole-1,3(2H)-dione) has been characterized as a high-affinity and potent 5-HT(1A)R agonist (K(i) = 5.9 nM, EC(50) = 21.8 nM) and exhibits neuroprotective effect in neurotoxicity assays in primary cell cultures from rat hippocampus and in the MCAO model of focal cerebral ischemia in rats.

Functions of 5-HT2A receptor and its antagonists in the cardiovascular system

The serotonin (5-hydroxytryptamine, 5-HT) receptors have conventionally been divided into seven subfamilies, most of which have several subtypes. Among them, 5-HT(2A) receptor is associated with the contraction of vascular smooth muscle, platelet aggregation and thrombus formation and coronary artery spasms. Accordingly, selective 5-HT(2A) antagonists may have potential in the treatment of cardiovascular diseases. Sarpogrelate, a selective 5-HT(2A) antagonist, has been introduced clinically as a therapeutic agent for the treatment of ischemic diseases associated with thrombosis. Molecular modeling studies also suggest that sarpogrelate is a 5-HT(2A) selective antagonist and is likely to have pharmacological effects beneficial in the treatment of cardiovascular diseases. This review describes the above findings as well as the signaling linkages of the 5-HT(2A) receptors and the mode of agonist binding to 5-HT(2A) receptor using data derived from molecular modeling and site-directed mutagenesis.

LB50053: a 5-hydroxytrypamine(1a) agent with a high binding affinity and a potency evoking a K(+) current

The newly synthesized N-substituted derivative of 3-aryl-pyrrolidine LB50053, 2-[4-[3-(4-fluoro)-phenylpyrrolidine-1-yl] - butyl]-1,2- benzisothiazol -3(2H)-one-1,1-dioxide, was studied in receptor-binding assays and in electrophysiological measurements. Competitive binding experiments with various radioligands to the rat fore-brain revealed that the (S)-enantiomer of LB50053 had a high affinity (Ki 4.2 nmol/l) and a high selectivity for 5-HT(1A) receptors as compared with 5-HT(2A), D(1) dopamine, D(2) dopamine, or (alpha(2)-adrenergic receptor. In Xenopus oocytes, where coupling of the 5-HT(1A) receptor to the G protein activated inwardly rectifying K(+) channel 1(GIRK1) was established, (S)-LB50053 evoked an inward K(+) current through GIRK1 in a manner consistent with a partial agonism. The K(d) value deduced from the dose-response relationships of the 5-HT(1A) receptor full agonist 8-OH-2-(di-n-propylamino)-1,2,3,4-tetrahydronaphthalene and (S)-LB50053 according to Waud analysis was 64.60 nmol/l. These results demonstrate that LB50053 is a 5-HT(1A) receptor partial agonist and thus can be used asa therapeutic or pharmacological research tool for 5-HT(1A) receptor mediated events in the future.