The selective glucocorticoid receptor antagonist CORT 108297 decreases neuroendocrine stress responses and immobility in the forced swim test

Pre-clinical and clinical studies have employed treatment with glucocorticoid receptor (GR) antagonists in an attempt to limit the deleterious behavioral and physiological effects of excess glucocorticoids. Here, we examined the effects of GR antagonists on neuroendocrine and behavioral stress responses, using two compounds: mifepristone, a GR antagonist that is also a progesterone receptor antagonist, and CORT 108297, a specific GR antagonist lacking anti-progestin activity. Given its well-documented impact on neuroendocrine and behavioral stress responses, imipramine (tricyclic antidepressant) served as a positive control. Male rats were treated for five days with mifepristone (10 mg/kg), CORT 108297 (30 mg/kg and 60 mg/kg), imipramine (10 mg/kg) or vehicle and exposed to forced swim test (FST) or restraint stress. Relative to vehicle, imipramine potently suppressed adrenocorticotropin hormone (ACTH) responses to FST and restraint exposure. Imipramine also decreased immobility in the FST, consistent with antidepressant actions. Both doses of CORT 108297 potently suppressed peak corticosterone responses to FST and restraint stress. However, only the higher dose of CORT 108297 (60 mg/kg) significantly decreased immobility in the FST. In contrast, mifepristone induced protracted secretion of corticosterone in response to both stressors, and modestly decreased immobility in the FST. Taken together, the data indicate distinct effects of each compound on neuroendocrine stress responses and also highlight dissociation between corticosterone responses and immobility in the FST. Within the context of the present study, our data suggest that CORT 108297 may be an attractive alternative for mitigating neuroendocrine and behavioral states associated with excess glucocorticoid secretion.     

Differences in degree of trapping between AR-R15896 and other uncompetitive NMDA receptor antagonists

Summary. NMDA antagonists like AR-R15896 have been selected on the basis of their good therapeutic indices. As Dr. Rogawski has pointed out, there may be a number of molecular factors which can improve the therapeutic index of NMDA antagonists. In this paper we will consider three factors; use-dependence, low affinity/fast kinetics, and partial trapping. Received August 31, 1999 Accepted September 3, 1999     

Synthesis and SAR studies of chiral non-racemic dexoxadrol analogues as uncompetitive NMDA receptor antagonists

A series of chiral non-racemic dexoxadrol analogues with various substituents in position 4 of the piperidine ring was synthesized and pharmacologically evaluated. Only the enantiomers having (S)-configuration at the 2-position of the piperidine ring and 4-position of the dioxolane ring were considered. Key steps in the synthesis were an imino-Diels-Alder reaction of enantiomerically pure imine (S)-13, which had been obtained from d-mannitol, with Danishefsky's Diene 14 and the replacement of the p-methoxybenzyl protective group with a Cbz-group. It was shown that (S,S)-configuration of the ring junction (position 2 of the piperidine ring and position 4 of the dioxolane ring) and axial orientation of the C-4-substituent ((4S)-configuration) are crucial for high NMDA receptor affinity. 2-(2,2-Diphenyl-1,3-dioxolan-4-yl)piperidines with a hydroxy moiety ((S,S,S)-5, K(i)=28nM), a fluorine atom ((S,S,S)-6, WMS-2539, K(i)=7nM) and two fluorine atoms ((S,S)-7, K(i)=48nM) in position 4 represent the most potent NMDA antagonists with high selectivity against σ(1) and σ(2) receptors and the polyamine binding site of the NMDA receptor. The NMDA receptor affinities of the new ligands were correlated with their electrostatic potentials, calculated gas phase proton affinities (negative enthalpies of deprotonation) and dipole moments. According to these calculations decreasing proton affinity and increasing dipole moment are correlated with decreasing NMDA receptor affinity.     

Design of subtype selective melatonin receptor agonists and antagonists.

Studies of the physiological actions of melatonin have been hindered by the lack of specific, potent and subtype selective agonists and antagonists. In the present study, we describe the utility of a melanophore cell line from Xenopus laevis for exploring structure-activity relationships among novel melatonin analogues and report a novel MT2-selective agonist (IIK7) and MT2-selective receptor antagonist (K185). IIK7 is a potent melatonin receptor agonist in the melanophore model, and in NIH3T3 cells expressing human mt1 and MT2 receptor subtypes. In radioligand binding experiments IIK7 is 90-fold selective for the MT2 subtype. K185 is devoid of agonist activity, but acts as a competitive melatonin antagonist in melanophores. A low concentration (10(-9) M) antagonizes melatonin inhibition of forskolin stimulation of cyclic AMP in NIH3T3 cells expressing human MT2 receptors, but has no effect in cells expressing mt1 receptors. In binding assays, K185 is 140-fold selective for the MT2 subtype.     

Effect of selective muscarinic receptor agonists and antagonists on active-avoidance learning acquisition in rats

Effect of some selective muscarinic receptor agonists and antagonists was investigated on learning acquisition in an active-avoidance paradigm in rats which records an anticipatory conditioned avoidance apart from the classical conditioned avoidance response. The muscarinic M1 agonists, arecholine, pilocarpine and McN-A-343, facilitated learning acquisition, which was attenuated by the selective M1 antagonist, pirenzepine. On the other hand, M2 receptor agonist, carbachol, and physostigmine, induced a dose-related dual response, with lower doses retarding and higher doses facilitating the learning acquisition. The former effect was attenuated by gallamine, a muscarinic M2 antagonist, while the latter response was inhibited by pirenzepine, indicating that these putative M2 receptor agonist lose their receptor specificity on dose increment. The selective M2 receptor antagonists, gallamine and AF-DX 116, facilitated learning acquisition, which was inhibited by pirenzepine and the acetylcholine synthesis inhibitor hemicholinium. The results support the cholinergic hypothesis of learning and memory and indicate that M1 receptor agonists and M2 receptor antagonists are likely to prove beneficial in memory deficits. The data also indicates that the clinical dose of some drugs, like physostigmine, needs to be carefully established for optimum therapeutic benefit.     

Effects of NMDA receptor antagonists on nociceptive responsesin vivo: Comparison of antagonists acting at the glycine site with uncompetitive antagonists

Summary We have shown that members of a new series of tricyclic pyridophthalazine diones, defined as glycine_B site NMDA antagonistsin vitro, are selective and systemically active NMDA antagonistsin vivo. In electrophysiological tests in -chloralose anaesthetised rats, these compounds reduced nociceptive reflex responses. In conscious rats they displayed analgesic properties. These glycine_B antagonists were compared electrophysiologically with several uncompetitive NMDA channel blockers. The degree of voltage dependence previously reportedin vitro related to the effectiveness of the agents against different amplitude nociceptive responses of spinal cord neuronesin vivo.     

The involvement of NMDA and AMPA receptors in the mechanism of antidepressant-like action of zinc in the forced swim test

Antidepressant-like activity of zinc in the forced swim test (FST) was demonstrated previously. Enhancement of such activity by joint administration of zinc and antidepressants was also shown. However, mechanisms involved in this activity have not yet been established. The present study examined the involvement of the NMDA and AMPA receptors in zinc activity in the FST in mice and rats. Additionally, the influence of zinc on both glutamate and aspartate release in the rat brain was also determined. Zinc-induced antidepressant-like activity in the FST in both mice and rats was antagonized by N-methyl-d-aspartic acid (NMDA, 75 mg/kg, i.p.) administration. Moreover, low and ineffective doses of NMDA antagonists (CGP 37849, L-701,324, d-cycloserine, and MK-801) administered together with ineffective doses of zinc exhibit a significant reduction of immobility time in the FST. Additionally, we have demonstrated the reduction of immobility time by AMPA receptor potentiator, CX 614. The antidepressant-like activity of both CX 614 and zinc in the FST was abolished by NBQX (an antagonist of AMPA receptor, 10 mg/kg, i.p.), while the combined treatment of sub-effective doses of zinc and CX 614 significantly reduces the immobility time in the FST. The present study also demonstrated that zinc administration potentiated a veratridine-evoked glutamate and aspartate release in the rat’s prefrontal cortex and hippocampus. The present study further suggests the antidepressant properties of zinc and indicates the involvement of the NMDA and AMPA glutamatergic receptors in this activity.     

Acute restraint stress produces behavioral despair in weanling rats in the forced swim test

Stressful experiences in the rat during early life increase the vulnerability to later signs of behavioral despair in adulthood, reflected in increased immobility in the forced swim test (FST). However, the possible immediate effects of stress in weanling rats have only been partially described. The present study tested whether a single session of mild restraint stress modifies immobility in the FST in 21-day-old Wistar rats. After evaluating any possible changes in locomotion using the open field test (OFT), the latency and total duration of immobility were assessed in a single FST session. Regardless of gender, mild restraint stress significantly reduced crossings in the OFT, shortened the latency to the first period of immobility, and increased immobility in the FST compared with a control group devoid of stress. We conclude that a single mild physical stress session, as early as postnatal day 21, produces signs of behavioral despair.     

Intracerebroventricular administration of neuronostatin induces depression-like effect in forced swim test of mice

Neuronostatin is a recently discovered endogenous bioactive peptide that is encoded by pro-mRNA of somatostatin. In the present study, we investigated the effect of neuronostatin on mood regulation in the forced swim test of mice. Our results showed intracerebroventricular (i.c.v.) administration of neuronostatin produced an increase in the immobility time, suggesting that neuronostatin induced depression-like effect. In order to rule out the possibility that neuronostatin had increased immobility time by a non-specific reduction in general activity, the effect of neuronostatin on locomotor activity was examined. Neuronostatin had no influence on locomotor activity in mice. In addition, the depression-like effect of neuronostatin was completely reversed by melanocortin 3/4 receptor antagonist SHU9119 or GABAA receptor antagonist bicuculline, but not by opioid receptor antagonist naloxone. These data suggested that the depression-like effect induced by i.c.v. administered neuronostatin was dependent upon the central melanocortin system and GABAA receptor. In conclusion, the results of this study report that neuronostatin induces depression-like effect. These findings reveal that neuronostatin is a new neuropeptide with an important role in regulating depressive behavior.     

Possible involvement of nitric oxide (NO) signaling pathway in the antidepressant-like effect of MK-801(dizocilpine), a NMDA receptor antagonist in mouse forced swim test

L-arginine-nitric oxide (NO)-cyclic guanosine monophosphate (cGMP) is an important signaling pathway involved in depression. With this information, the present study aimed to study the involvement of this signaling pathway in the antidepressant-like action of MK-801 (dizocilpine; N-methyl-d-aspartate receptor antagonist) in the mouse forced-swim test. Total immobility period was recorded in mouse forced swim test for 6 min. MK-801 (5-25 microg/kg., ip) produced a U-shaped curve in reducing the immobility period. The antidepressant-like effect of MK-801 (10 microg/kg, ip) was prevented by pretreatment with L-arginine (750 mg/kg, ip) [substrate for nitric oxide synthase (NOS)]. Pretreatment of mice with 7-nitroindazole (7-NI) (25 mg/kg, ip) [a specific neuronal nitric oxide synthase inhibitor] produced potentiation of the action of subeffective dose of MK-801 (5 microg/kg, ip). In addition, treatment of mice with methylene blue (10 mg/kg, ip) [direct inhibitor of both nitric oxide synthase and soluble guanylate cyclase] potentiated the effect of MK-801 (5 microg/kg, ip) in the forced-swim test. Further, the reduction in the immobility period elicited by MK-801 (10 microg/kg, ip) was also inhibited by pretreatment with sildenafil (5 mg/kg, ip) [phosphodiesterase 5 inhibitor]. The various modulators used in the study and their combination did not produce any changes in locomotor activity per se and in combination with MK-801. MK-801 however, at higher doses (25 microg/kg, ip) produced hyperlocomotion. The results demonstrated the involvement of nitric oxide signaling pathway in the antidepressant-like effect of MK-801 in mouse forced-swim test.     

Individual differences in the elevated plus-maze and the forced swim test

The elevated plus-maze is an apparatus composed of enclosed and open (elevated) arms and time spent in the open arms by a rat can be increased/decreased by anxiolytic/anxiogenic agents. In the forced swim test, floating behavior is used as an index of behavioral despair and can be decreased by antidepressant agents. As the comorbidity between anxiety and depression is a remarkable issue in human behavioral disorders, a possible relationship between the behaviors seen in the cited tests is of great relevance. In the present study, fifty-four male rats (Rattus norvegicus) were submitted to a plus-maze session and to a 2-day forced swim protocol. According to their time in the open arms, they were divided into three groups: Low Open, Medium Open and High Open. Some plus-maze measures were found to be coherent with time in the open arms and are suggested to also be reliable anxiety indexes. In the forced swim test, the Low Open group showed decreases in floating duration from forced swim Session 1 to Session 2, an alteration opposite to that observed in the other groups (particularly, the Medium Open group). The Low Open group also showed increases in floating latency, again in sharp contrast with the alteration found in the other groups. Accordingly, positive and negative correlation were found between time in the open arms and floating duration and latency, respectively. Results are compared to previous studies and mediation of the effect by reactivity to aversive stimulation or alterations induced by open arm exposure is discussed.     

Subtype selective NMDA receptor antagonists: evaluation of some novel alkynyl analogues

A benzylpiperidine analogue with an acetylenic linker, 5-(3-[4-(4-fluorobenzyl)-piperidin-1-yl]-prop-1-ynyl)-1,3-dihydrobenzimidazol-2-one (3), was identified as a chemical lead with excellent activity at the NR1A/2B receptor (IC50=3 nM). Efforts to optimize this activity led to focused modifications around the structural motif of 3. The synthesis and SAR studies are discussed.     

Effect of opiate receptor agonists and antagonists on maternal aggression in rats

The behavioral effects of opiate agonists and antagonists were studied on the female aggression model. Mu-agonist buprenorphine more selectively decreased maternal aggression than kappa-agonist tifluadom. Kappa-agonists (bremazocine, tifluadom) increased passive defence in lactating female rats. Ethopharmacological data shows predominant involvement of brain mu-opiate receptor system in the integrative processes of maternal behavior and maternal aggression in particular.     

In vitro characterization of novel NR2B selective NMDA receptor antagonists

N-Methyl-D-aspartate (NMDA) subunit specific receptor antagonism has potential therapeutic application for multiple CNS pathologies. MERCK 1, MERCK 2, and MERCK 3 are novel NR2B subtype selective NMDA receptor antagonists. The affinity and the kinetic mechanism of inhibition by these antagonists and ifenprodil were investigated using the whole-cell configuration of the patch clamp technique, calcium flux, and radioligand binding on a mouse cell line L(tk-) expressing recombinant human heteromeric NMDA receptors consisting of NR1a/NR2B subunit combinations. The rank order of potency, as determined by electrophysiology, was ifenprodil相似文献   

Changes in progesterone metabolites in the hippocampus can modulate open field and forced swim test behavior of proestrous rats

The purpose of these experiments was to test the hypothesis that attenuating the endogenous increase of the 5alpha-reduced progesterone metabolite 5alpha-pregnan-3alpha-ol-20-one (3alpha,5alpha-THP) in the hippocampus will alter anxiety and depression behavior of proestrous rats. In Experiment 1, anxiety (open field) and depression (forced swim test) behavior was compared of rats that should have high (proestrous) and low (diestrous and male rats) endogenous hippocampal 3alpha,5alpha-THP. Proestrous rats exhibited more anxiolytic-like (increased central entries in the open field) and anti-depressant-like (less immobility in the forced swim test) behavior than diestrous or male rats. In Experiments 2 and 3, respectively, systemic and intrahippocampal finasteride, a 5alpha-reductase inhibitor which attenuates progesterone's metabolism to 3alpha,5alpha-THP, versus vehicle administration to proestrous rats was compared for effects on open field and forced swim test behavior. Systemic or intrahippocampal finasteride decreased central entries in the open field and increased immobility in the forced swim tests compared to vehicle administration. In Experiment 4, the effects of systemic and intrahippocampal finasteride vs vehicle administration on hippocampal 3alpha,5alpha-THP of proestrous rats was examined. Finasteride, SC or intrahippocampally, reduced 3alpha,5alpha-THP in the hippocampus compared to vehicle administration. Together these data suggest that variations in 3alpha,5alpha-THP levels in the hippocampus may mitigate proestrous changes in anxiety and depressive behavior of cycling rats.     

The design and pharmacology of novel selective muscarinic agonists and antagonists

The muscarinic pharmacology of C1-methyl-substituted chiral compounds related to McN-A-343 and of (R)- and (S)-dimethindene has been studied. Among the McN-A-343 analogues, the (S)-enantiomers were more potent and had higher affinity than the (R)-isomers. The quaternary compound (S)-BN 228 was found to be the most potent M1-selective agonist known today (pEC50: M1/rabbit vas deferens = 7.83; M2/guinea-pig atria = 6.35; M3/guinea-pig ileum = 6.29). In both the atria and ileum the tertiary carbamate, (S)-4-F-MePyMcN, was a competitive antagonist (pA2 value = 7.39 and 6.82, respectively). In contrast, in rabbit vas deferens (S)-4-F-MePyMcN was a potent partial agonist (pEC50 = 7.22; apparent efficacy = 0.83). These results indicate that (S)-4-F-MePyMcN might be a useful tool to study M1 receptor-mediated effects involved in central cholinergic function. (S)-Dimethindene was a potent M2-selective antagonist (pA2 = 7.86/atria; pKi = 7.8/rat heart) with lower affinities for the M1 (pA2 = 6.36/rat duodenum; pKi = 7.1/NB-OK 1 cells), M3 (pA2 = 6.92/guinea-pig ileum; pKi = 6.7/rat pancreas) and M4 receptors (pKi = 7.0/rat striatum). It was more potent (up to 41-fold) than the (R)-isomer. In contrast, the stereoselectivity was inverse at ileal H1 receptors (pA2: (R)-isomer = 9.42; (S)-isomer = 7.48). Thus, (S)-dimethindene could be a valuable agent to test the hypothesis that M2 antagonists show beneficial effects in the treatment of cognitive disorders. It might also become the starting point for the development of diagnostic tools for quantifying M2 receptors in the CNS with PET imaging.     

Berberine produces antidepressant-like effects in the forced swim test and in the tail suspension test in mice

This study investigated the effect of berberine (BER) in the mouse forced swim test (FST) and in the tail suspension test (TST), two models predictive of antidepressant activity. We also investigated the antidepressant-like mechanism of BER by the combination of the desipramine [DES, an inhibitor of reuptake of noradrenaline (NA) and serotonin (5-HT)], maprotiline (MAP, selective NA reuptake inhibitor), fluoxetine (FLU, selective 5-HT reuptake inhibitor) and moclobemide [MOC, monoamine oxidase (MAO) A inhibitor). Then we further measured the levels of monoamines [NA, dopamine (DA) and 5-HT) in mice striatum, hippocampus and frontal cortex. The results show that BER (10, 20 mg/kg, p.o.), significantly reduced the immobility time during the FST and the TST. The immobility time after treatment with BER (20 mg/kg, p.o.) in FST was augmented by DES, FLU and MOC, and not affected by MAP. Furthermore, BER (20 mg/kg, p.o.) increased NA and 5-HT levels in the hippocampus and frontal cortex. Our findings support the view that BER exerts antidepressant-like effect. The antidepressant-like mechanism of BER may be related to the increase in NA and 5-HT levels in the hippocampus and frontal cortex.     

Modulation of glutamate-induced uncompetitive blocker binding to the NMDA receptor by temperature and by glycine

The effect of temperature on the binding of [3H]-N-[1-(2-thienyl)cyclohexyl]piperidine [( 3H]TCP) to the ion channel of the N-methyl-D-aspartate (NMDA) receptors was studied in washed rat brain-cortex membranes. Raising the temperature from 5 to 33 degrees C resulted in a significant increase in the association rates of [3H]TCP binding measured in the presence of 1 microM glutamate and 1 microM glycine, but was less effective in the absence of the added agonists. No such effects of temperature on the dissociation rates of [3H]TCP-receptor complexes were observed. In the absence of agonists, neither the association nor the dissociation binding components varied with temperature, suggesting a diffusion-controlled limitation of access of the ligand to its site within the nonactivated NMDA receptor. No evidence was found for a temperature-dependent change in the density of [3H]TCP binding sites or for heterogeneity of [3H]TCP binding sites associated with the NMDA receptor, even though when approaching equilibrium the binding kinetics in the presence of glutamate and glycine deviated from an ordinary bimolecular reaction scheme. The data were fitted instead to a two-exponent binding function, comprising the sum of a fast and a slow binding component. Their corresponding time constants exhibited an increase with temperature, and the increase of each one was correlated significantly with the corresponding decrease in the equilibrium binding constant; however, there was no temperature-related change in the relative proportions of the two components, with the fast binding component (alpha) accounting for 50-70% of the site population.(ABSTRACT TRUNCATED AT 250 WORDS)     

Using the rat forced swim test to assess antidepressant-like activity in rodents

The forced swim test (FST) is one of the most commonly used animal models for assessing antidepressant-like behavior. This protocol details using the FST in rats, which takes place over 48 h and is followed by the video analysis of the behavior. The swim test involves the scoring of active (swimming and climbing) or passive (immobility) behavior when rodents are forced to swim in a cylinder from which there is no escape. There are two versions that are used, namely the traditional and modified FSTs, which differ in their experimental setup. For both versions, a pretest of 15 min (although a number of laboratories have used a 10-min pretest with success) is included, as this accentuates the different behaviors in the 5-min swim test following drug treatment. Reduction in passive behavior is interpreted as an antidepressant-like effect of the manipulation, provided it does not increase general locomotor activity, which could provide a false positive result in the FST.