ABSTRACT
Noncompetitive N-methyl-D-aspartate (NMDA) blockers induce schizophrenic-like symptoms in humans, presumably by impairing glutamatergic transmission. Therefore, a compound potentiating this neurotransmission, by increasing extracellular levels of glycine (a requisite co-agonist of glutamate), could possess antipsychotic activity. Blocking the glycine transporter-1 (GlyT1) should, by increasing extracellular glycine levels, potentiate glutamatergic neurotransmission. SSR504734, a selective and reversible inhibitor of human, rat, and mouse GlyT1 (IC50=18, 15, and 38 nM, respectively), blocked reversibly the ex vivo uptake of glycine (mouse cortical homogenates: ID50: 5 mg/kg i.p.), rapidly and for a long duration. In vivo, it increased (minimal efficacious dose (MED): 3 mg/kg i.p.) extracellular levels of glycine in the rat prefrontal cortex (PFC). This resulted in an enhanced glutamatergic neurotransmission, as SSR504734 potentiated NMDA-mediated excitatory postsynaptic currents (EPSCs) in rat hippocampal slices (minimal efficacious concentration (MEC): 0.5 microM) and intrastriatal glycine-induced rotations in mice (MED: 1 mg/kg i.p.). It normalized activity in rat models of hippocampal and PFC hypofunctioning (through activation of presynaptic CB1 receptors): it reversed the decrease in electrically evoked [3H]acetylcholine release in hippocampal slices (MEC: 10 nM) and the reduction of PFC neurons firing (MED: 0.3 mg/kg i.v.). SSR504734 prevented ketamine-induced metabolic activation in mice limbic areas and reversed MK-801-induced hyperactivity and increase in EEG spectral energy in mice and rats, respectively (MED: 10-30 mg/kg i.p.). In schizophrenia models, it normalized a spontaneous prepulse inhibition deficit in DBA/2 mice (MED: 15 mg/kg i.p.), and reversed hypersensitivity to locomotor effects of d-amphetamine and selective attention deficits (MED: 1-3 mg/kg i.p.) in adult rats treated neonatally with phencyclidine. Finally, it increased extracellular dopamine in rat PFC (MED: 10 mg/kg i.p.). The compound showed additional activity in depression/anxiety models, such as the chronic mild stress in mice (10 mg/kg i.p.), ultrasonic distress calls in rat pups separated from their mother (MED: 1 mg/kg s.c.), and the increased latency of paradoxical sleep in rats (MED: 30 mg/kg i.p.). In conclusion, SSR504734 is a potent and selective GlyT1 inhibitor, exhibiting activity in schizophrenia, anxiety and depression models. By targeting one of the primary causes of schizophrenia (hypoglutamatergy), it is expected to be efficacious not only against positive but also negative symptoms, cognitive deficits, and comorbid depression/anxiety states.
Subject(s)
Benzamides/pharmacology , Brain Chemistry/drug effects , Enzyme Inhibitors/pharmacology , Glycine Plasma Membrane Transport Proteins/antagonists & inhibitors , Neurons/drug effects , Piperidines/pharmacology , Acetylcholine/metabolism , Action Potentials/drug effects , Amphetamine/pharmacology , Analysis of Variance , Animals , Animals, Newborn , Behavior, Animal/drug effects , Carbon Isotopes/metabolism , Cells, Cultured , Cerebral Cortex/cytology , Circadian Rhythm/drug effects , Dopamine Uptake Inhibitors/pharmacology , Dose-Response Relationship, Drug , Drug Interactions , Enzyme Inhibitors/chemistry , Excitatory Amino Acid Antagonists/pharmacology , Excitatory Postsynaptic Potentials/drug effects , Female , Glycine/metabolism , Hippocampus/cytology , Humans , In Vitro Techniques , Inhibitory Concentration 50 , Male , Mice , Motor Activity/drug effects , Neural Inhibition/drug effects , Neurons/physiology , Patch-Clamp Techniques/methods , Rats , Rats, Sprague-Dawley , Reflex, Startle/drug effectsABSTRACT
The biochemical and pharmacological properties of a novel non-peptide antagonist of the bradykinin (BK) B(1) receptor, SSR240612 [(2R)-2-[((3R)-3-(1,3-benzodioxol-5-yl)-3-[[(6-methoxy-2-naphthyl)sulfonyl]amino]propanoyl)amino]-3-(4-[[2R,6S)-2,6-dimethylpiperidinyl]methyl]phenyl)-N-isopropyl-N-methylpropanamide hydrochloride] were evaluated. SSR240612 inhibited the binding of [(3)H]Lys(0)-des-Arg(9)-BK to the B(1) receptor in human fibroblast MRC5 and to recombinant human B(1) receptor expressed in human embryonic kidney cells with inhibition constants (K(i)) of 0.48 and 0.73 nM, respectively. The compound selectivity for B(1) versus B(2) receptors was in the range of 500- to 1000-fold. SSR240612 inhibited Lys(0)-desAr(9)-BK (10 nM)-induced inositol monophosphate formation in human fibroblast MRC5, with an IC(50) of 1.9 nM. It also antagonized des-Arg(9)-BK-induced contractions of isolated rabbit aorta and mesenteric plexus of rat ileum with a pA(2) of 8.9 and 9.4, respectively. Antagonistic properties of SSR240612 were also demonstrated in vivo. SSR240612 inhibited des-Arg(9)-BK-induced paw edema in mice (3 and 10 mg/kg p.o. and 0.3 and 1 mg/kg i.p.). Moreover, SSR240612 reduced capsaicin-induced ear edema in mice (0.3, 3 and 30 mg/kg p.o.) and tissue destruction and neutrophil accumulation in the rat intestine following splanchnic artery occlusion/reperfusion (0.3 mg/kg i.v.). The compound also inhibited thermal hyperalgesia induced by UV irradiation (1 and 3 mg/kg p.o.) and the late phase of nociceptive response to formalin in rats (10 and 30 mg/kg p.o.). Finally, SSR240612 (20 and 30 mg/kg p.o.) prevented neuropathic thermal pain induced by sciatic nerve constriction in the rat. In conclusion, SSR240612 is a new, potent, and orally active specific non-peptide bradykinin B(1) receptor antagonist.
Subject(s)
Analgesics/pharmacology , Bradykinin B1 Receptor Antagonists , Dioxoles/pharmacology , Ileum/drug effects , Sulfonamides/pharmacology , Administration, Oral , Analgesics/therapeutic use , Animals , CHO Cells , Cricetinae , Disease Models, Animal , Edema/chemically induced , Edema/drug therapy , Formaldehyde , Humans , Ileum/metabolism , Male , Mice , Rabbits , Rats , Rats, Sprague-Dawley , Reperfusion Injury/drug therapyABSTRACT
SSR240600 [(R)-2-(1-[2-[4-[2-[3,5-bis(trifluoromethyl)phenyl]acetyl]-2-(3,4-dichlorophenyl)-2-morpholinyl]ethyl]-4-piperidinyl)-2-methylpropanamide], a new nonpeptide tachykinin neurokinin 1 (NK1) receptor antagonist, was evaluated against the neurochemical, electrophysiological, and behavioral effects provoked by direct activation of brain tachykinin NK1 receptors or by stress in guinea pigs. SSR240600 (0.1-10 mg/kg i.p. or p.o.) antagonized the excitatory effect of i.c.v. infusion of [Sar(9),Met(O2)(11)]substance P (SP) on the release of acetylcholine in the striatum of anesthetized and awake guinea pigs. This antagonistic action was still observed after repeated administration of SSR240600 (5 days, 10 mg/kg p.o., once a day). SSR240600 (10 mg/kg i.p.) inhibited the phosphorylation of the cAMP response element-binding protein in various brain regions induced by i.c.v. administration of [Sar9,Met(O2)(11)]SP. In slice preparations, neuronal firing of the locus coeruleus (LC) neurons elicited by the application of [Sar9,Met(O2)(11)]SP was suppressed by SSR240600 at 100 nM. Norepinephrine release in the prefrontal cortex, elicited either by an intra-LC application of [Sar9,Met(O2)(11)]SP or by an i.c.v administration of corticotropin-releasing factor, was reduced by SSR240600 (0.3-1 mg/kg and 1-10 mg/kg i.p., respectively). SSR240600 (1-10 mg/kg i.p.) inhibited vocalizations induced in adult guinea pigs by an i.c.v. administration of the NK1 receptor agonist, GR73632 [D-Ala-[L-Pro9,Me-Leu8]substance P(7-11)]. Furthermore, SSR240600 (1-10 mg/kg i.p.) inhibited distress vocalizations produced in guinea pig pups by maternal separation. SSR240600 also reduced maternal separation-induced increase in the number of neurons displaying NK1 receptor internalization in the amygdala. Finally, SSR240600 counteracted the increase in body temperature induced by isolation stress. In conclusion, SSR240600 is able to antagonize various NK1 receptor-mediated as well as stress-mediated effects in the guinea pig.
