Tricyclic imidazole antagonists of the Neuropeptide S Receptor.

A new structural class of potent antagonists of the Neuropeptide S Receptor (NPSR) is reported. High-throughput screening identified a tricyclic imidazole antagonist of NPSR, and medicinal chemistry optimization of this structure was undertaken to improve potency against the receptor as well as CNS penetration. Detailed herein are synthetic and medicinal chemistry studies that led to the identification of antagonists 15 and NPSR-PI1, which demonstrate potent in vitro NPSR antagonism and central exposure in vivo.

Synthesis and evaluation of a new series of Neuropeptide S receptor antagonists.

Administration of Neuropeptide S (NPS) has been shown to produce arousal, that is, independent of novelty and to induce wakefulness by suppressing all stages of sleep, as demonstrated by EEG recordings in rat. Medicinal chemistry efforts have identified a quinolinone class of potent NPSR antagonists that readily cross the blood-brain barrier. We detail here optimization efforts resulting in the identification of a potent NPSR antagonist which dose-dependently and specifically inhibited (125)I-NPS binding in the CNS when administered to rats.

NR2B-selective N-methyl-D-aspartate antagonists: synthesis and evaluation of 5-substituted benzimidazoles.

Two classes of 5-substituted benzimidazoles were identified as potent antagonists of the NR2B subtype of the N-methyl-d-aspartate (NMDA) receptor. Selected compounds show very good selectivity versus the NR2A, NR2C, and NR2D subtypes of the NMDA receptor as well as versus hERG-channel activity and alpha(1)-adrenergic binding. Benzimidazole 37a shows excellent activity in the carrageenan-induced mechanical hyperalgesia assay in rats as well as good pharmacokinetic behavior in dogs.

Generation and characterization of a cell line with inducible expression of Ca(v)3.2 (T-type) channels.

Establishment of stable cell lines that constitutively express Ca(2+) channels at high density and that are useful for in vitro studies may be complicated by problems with seal quality and duration during whole-cell patch-clamp electrophysiology. The current studies describe the generation and characterization of cells that express the human alpha1H T-type Ca(2+) channel under the control of a tetracycline-inducible expression system. Western blot and immunostaining studies revealed that expression of the alpha1H protein occurred only in the presence of tetracycline. Using the whole-cell patch-clamp method, the cells displayed peak inward currents of 1.15 +/- 0.14 nA in response to voltage-clamp steps. The T-type Ca(2+) current was inhibited by the T-type Ca(2+) channel antagonist, mibefradil, with an IC(50) of 160 nM. This cell line, with inducible channel expression, sealed with longer duration during whole-cell patch-clamp recording when compared with a cell line that constitutively expresses the alpha1H Ca(2+) channel. Ca(2+) influx through this channel could also be detected after the addition of extracellular Ca(2+). The amount of Ca(2+) influx was dependent on the [Ca](o) with an EC(50) of 4 mM. The Ca(2+) influx was also inhibited by mibefradil with a potency (IC(50) = 183 nM) similar to that observed in the voltage-clamp studies. Overall, this inducible alpha1H Ca(2+) channel-expressing cell line is useful for the study of human T-type Ca(2+) channel function, and offers advantages over a similar cell line that constitutively expresses the channel.

Cyclic benzamidines as orally efficacious NR2B-selective NMDA receptor antagonists.

A novel series of cyclic benzamidines was synthesized and shown to exhibit NR2B-subtype selective NMDA antagonist activity. Compound 29 is orally active in a carrageenan-induced rat hyperalgesia model of pain.

Orally efficacious NR2B-selective NMDA receptor antagonists.

A novel series of benzamidines was synthesized and shown to exhibit NR2B-subtype selective NMDA antagonist activity. Compound 31 is orally active in a carrageenan-induced rat hyperalgesia model of pain and shows no motor coordination side effects.