(R)-ketamine attenuates neurodevelopmental disease-related phenotypes in a mouse model of maternal immune activation.

Infections during pregnancy are associated with an increased risk of neuropsychiatric disorders with developmental etiologies, such as schizophrenia and autism spectrum disorders (ASD). Studies have shown that the animal model of maternal immune activation (MIA) reproduces a wide range of phenotypes relevant to the study of neurodevelopmental disorders. Emerging evidence shows that (R)-ketamine attenuates behavioral, cellular, and molecular changes observed in animal models of neuropsychiatric disorders. Here, we investigate whether (R)-ketamine administration during adolescence attenuates some of the phenotypes related to neurodevelopmental disorders in an animal model of MIA. For MIA, pregnant Swiss mice received intraperitoneally (i.p.) lipopolysaccharide (LPS; 100 µg/kg/day) or saline on gestational days 15 and 16. The two MIA-based groups of male offspring received (R)-ketamine (20 mg/kg/day; i.p.) or saline from postnatal day (PND) 36 to 50. At PND 62, the animals were examined for anxiety-like behavior and locomotor activity in the open-field test (OFT), as well as in the social interaction test (SIT). At PND 63, the prefrontal cortex (PFC) was collected for analysis of oxidative balance and gene expression of the cytokines IL-1ß, IL-6, and TGF-ß1. We show that (R)-ketamine abolishes anxiety-related behavior and social interaction deficits induced by MIA. Additionally, (R)-ketamine attenuated the increase in lipid peroxidation and the cytokines in the PFC of the offspring exposed to MIA. The present work suggests that (R)-ketamine administration may have a long-lasting attenuation in deficits in emotional behavior induced by MIA, and that these effects may be attributed to its antioxidant and anti-inflammatory activity in the PFC.

Psychopharmacological effects and safety of styryl-2-pyrones and dihydrostyryl-2-pyrones-rich fraction from Polygala sabulosa: absence of withdrawal syndrome and tolerance to anxiolytic-like and anticonvulsant effects.

OBJECTIVES: To investigate whether mice develop tolerance to the anxiolytic-like and anticonvulsant effects of subchronic treatment with EA (the styryl-2-pyrones and dihydrostyryl-2-pyrones-rich fraction of Polygala sabulosa), as well as any withdrawal symptoms after abrupt discontinuation; to compare the effects of EA with those of diazepam (DZP) on withdrawal-induced anxiety; and to evaluate the toxicity of EA according to OECD guidelines. METHODS: Male or female mice were acutely or subchronically treated with EA or DZP, and their tolerance to anxiolytic (evaluated in the elevated plus maze, EPM) and anticonvulsant effects (measured against pentylenetetrazole (PTZ)-induced convulsions) were investigated. Other groups received EA or DZP for 28 days followed by withdrawal, being the anxiety-like behaviour evaluated in the EPM. KEY FINDINGS: Both acute and subchronic treatments with EA induced an anxiolytic effect in the EPM. The anticonvulsant activity of DZP, but not EA, was reduced by protracted treatment. EA withdrawal retained the anxiolytic profile, while DZP withdrawal induced anxiogenesis. EA counteracted the anxiogenic-like actions of DZP withdrawal. EA has low toxicity as it did not cause any changes in the biochemical, haematological and histopathological markers. CONCLUSIONS: EA avoids the development of tolerance to its anxiolytic-like and anticonvulsant actions, and does not promote withdrawal syndrome. EA does not cause relevant toxic effects in rodents.

Evidence for involvement of NK3 receptors in the anxiogenic-like effect of SP6-11(C-terminal), a metabolite of substance P, in rats evaluated in the elevated plus-maze.

INTRODUCTION: Substance P (SP) is a neuropeptide widely expressed throughout the fear-processing pathways of the brain. SP is cleaved by several proteolytic enzymes in amino (N-) and carboxy (C-) terminal sequences, which can have biological activities per se. We have previously shown that the anxiogenic-like effects elicited by SP6-11(C-terminal), a specific metabolite of SP, are mediated via NK1 and NK2 receptors. Nevertheless, there are evidences that C-terminal fragments may have a greater affinity for NK3 receptors. OBJECTIVES: The aim of the present study was to further investigate the possible involvement of NK3 receptors in the anxiogenic-like effects induced by SP6-11(C-terminal). METHODS: Adult male Wistar rats were intracerebroventricularly (i.c.v.) treated with SR142801 (NK3 receptors antagonist) or vehicle one minute to prior SP6-11(C-terminal) or vehicle. Other experimental groups received SP6-11(C-terminal) or vehicle i.c.v. one minute prior to senktide (NK3 receptors agonist) or vehicle. After five minutes, the animals were behaviorally evaluated in the elevated plus-maze test (EPM). RESULTS: SR142801 (100 pmol) or SP6-11(C-terminal) (10 pmol) reduced all the parameters of open-arms exploration and increased the number of protected stretch-attend postures in the EPM, indicating an anxiogenic-like effect. Senktide (10 pmol) promoted an opposite effect on these behavioral parameters, characterizing an anxiolytic-like profile. Pretreatment with SR142801, in an ineffective dose, potentiated the SP6-11-induced anxiety, especially in the unprotected head-dipping and protected stretch-attend postures behaviors. Moreover, the anxiolytic-like effect induced by senktide (1 pmol) was prevented by SP6-11. CONCLUSIONS: Our results give support to the involvement of NK3 receptors in the anxiogenic-like actions of SP6-11(C-terminal), where this metabolite seems to behave as an antagonist, in a way similar to SR142801.

NK1 receptors antagonism of dorsal hippocampus counteract the anxiogenic-like effects induced by pilocarpine in non-convulsive Wistar rats.

Recent evidence supports a role for the substance P (SP) in the control of anxiety and epilepsy disorders. Aversive stimuli alter SP levels and SP immunoreactivity in limbic regions, suggesting that changes in SP-NK1 receptor signaling may modulate the neuronal excitability involved in seizures and anxiogenesis. The involvement of NK1 receptors of the dorsal hippocampus and lateral septum in the anxiogenic-like effects induced by a single injection of pilocarpine (PILO) was examined in non-convulsive rats evaluated in the elevated plus-maze (EPM). Male Wistar rats were systemically injected with methyl-scopolamine (1mg/kg) followed 30 min later by saline or PILO (350 mg/kg) and only rats that did not present status epilepticus were used. One month later, vehicle or FK888 (100 pmol) - an NK1 receptor antagonist - were infused in the dorsal hippocampus or the lateral septum of the rats and then behaviorally evaluated in the EPM. Previous treatment with PILO decreased the time spent in and the frequency of entries in the open arms of the EPM, besides altering risk-assessment behaviors such as the number of unprotected head-dipping, protected stretch-attend postures and the frequency of open-arms end activity, showing thus a long-lasting anxiogenic-like profile. FK888 did not show any effect per se but inhibited the anxiogenic responses induced by PILO when injected into the dorsal hippocampus, but not into the lateral septum. Our data suggest that SP-NK1 receptor signaling of the dorsal hippocampus is involved in the anxiogenic-like profile induced by PILO in rats evaluated in the EPM test.

GABA-A receptor modulators alter emotionality and hippocampal theta rhythm in an animal model of long-lasting anxiety.

The cholinergic system is implicated in emotional regulation. The injection of non-convulsant doses of the muscarinic receptor agonist pilocarpine (PILO) induces long-lasting anxiogenic responses in rats evaluated at different time-points (24h to 3 months). To investigate the underlying mechanisms, rats treated with PILO (150mg/kg) were injected 24h or 1 month later with an anxiolytic (diazepam, 1mg/kg, DZP) or anxiogenic (pentylenetetrazole, 15mg/kg, PTZ) drug and evaluated in the elevated plus-maze (EPM). Prefrontal cortex (PFC) and hippocampal (HIP) electroencephalographic recordings and acetylcolinesterase (AChE) activity were also analyzed after PILO treatment. Anxiogenic responses observed in the EPM 24h or 1 month after PILO treatment (e.g., decreased time spent and number of entries into the open arms of the maze) were blocked by DZP but not affected by PTZ. No epileptiform events were registered in the HIP or PFC at 24h or 1 month after PILO injection, but enhanced theta activity was observed in the HIP. DZP decreased hippocampal theta of PILO-treated rats in contrast with PTZ, which increased this parameter in saline- and PILO-treated rats. The HIP and PFC AChE activity did not change after PILO treatment. Our findings demonstrate that the long-term effects on the emotionality of rats induced by PILO are associated with electrophysiological changes in the HIP and sensitive to pharmacological manipulation of the GABAergic system. The present work may support this new research model of long-lasting anxiety, while also highlighting the muscarinic system as a potential target involved in anxiety disorders.

Anti-inflammatory lipoxin A4 is an endogenous allosteric enhancer of CB1 cannabinoid receptor.

Allosteric modulation of G-protein-coupled receptors represents a key goal of current pharmacology. In particular, endogenous allosteric modulators might represent important targets of interventions aimed at maximizing therapeutic efficacy and reducing side effects of drugs. Here we show that the anti-inflammatory lipid lipoxin A(4) is an endogenous allosteric enhancer of the CB(1) cannabinoid receptor. Lipoxin A(4) was detected in brain tissues, did not compete for the orthosteric binding site of the CB(1) receptor (vs. (3)H-SR141716A), and did not alter endocannabinoid metabolism (as opposed to URB597 and MAFP), but it enhanced affinity of anandamide at the CB1 receptor, thereby potentiating the effects of this endocannabinoid both in vitro and in vivo. In addition, lipoxin A(4) displayed a CB(1) receptor-dependent protective effect against ß-amyloid (1-40)-induced spatial memory impairment in mice. The discovery of lipoxins as a class of endogenous allosteric modulators of CB(1) receptors may foster the therapeutic exploitation of the endocannabinoid system, in particular for the treatment of neurodegenerative disorders.

Effects of social isolation and enriched environment on behavior of adult Swiss mice do not require hippocampal neurogenesis.

Housing conditions are important determinants of animal behavior. Their impact on behavioral output depends on the behavior of interest, species, strain, and age of the animal evaluated. In the present study, male Swiss mice reared from weaning up to 8 weeks in social isolation (SI8), in enriched environment (EE8) or in standard environment (SE8) were evaluated in the elevated plus-maze (EPM), open-field (OFT) and tail-suspension (TST) tests. The effect of housing for 6 weeks in EE followed by 2 weeks in SI (EE6SI2) and the opposite condition (SI6EE2) was also studied. Housing conditions are reported to affect hippocampal neurogenesis; therefore, the expression of doublecortin (DCX) in the dentate gyrus of the hippocampus (DG) of these mice was monitored. Data showed that SI8, EE8 and EE6SI2 reduced the stretching-attend postures in the EPM and explored more the center of the apparatus when compared to SE8. The time and the number of entries in the closed arms of the EPM was not affected indicating that effects of housing conditions in the EPM were not consequence of motor activity alteration. Accordingly, EE8 mice exploration of the OFT was similar to SE8. However, the SI8 mice explored the OFT more than the EE8 mice, suggesting hyperactivity induced by isolation. Behavior of Swiss mice in the TST was not altered, indicating that this test was not sensitive to the environmental changes in this mice strain. Compared to SE8, EE8 did not affect the number of DCX cells, whereas SI8, EE6SI2, and SI6EE2 decreased it. Taken together, our data suggest that the behavior of adult Swiss mice in the EPM and OFT was affected by environmental changes but that these changes seem to be independent of hippocampal neurogenesis.

Involvement of GABAergic non-benzodiazepine sites in the anxiolytic-like and sedative effects of the flavonoid baicalein in mice.

Baicalein (BA), one of the main flavonoids obtained from the Chinese medicinal herb Scutellaria baicalensis, usually exerts several pharmacological effects. In the central nervous system (CNS), BA exerts a protective effect on neurons against several neuronal insults among other effects, but it is not clear if this effect is due to its metabolite, baicalin. The purpose of the present study was to assess the anxiolytic-like and related properties of BA following its central administration (i.c.v.) in mice. BA (0.02, 0.2pmol) exerted an anxiolytic-like effect at low doses, increasing the time spent in open arms and the head-dipping whereas reducing the stretched-attend postures in the elevated plus-maze. BA also increased the duration of ether-induced sleep without affecting the pentylenetetrazol (PTZ)-induced convulsions. In addition, pretreatment with flumazenil (FMZ), PTZ, dehydroepiandrosterone sulfate (DHEAS), and dl-p-chlorophenilalanine ethyl ester (PCPA) were conducted in order to investigate its mechanism of action. PTZ and DHEAS, but not FMZ or PCPA, antagonized the BA's anxiolytic-like effect. Taken together our results showed that BA, when directly injected into the CNS, promotes anxiolytic-like and sedative effects, pharmacological activities dependent on GABAergic non-benzodiazepine sites but not on the 5-HT system.

Short- and long-term anxiogenic effects induced by a single injection of subconvulsant doses of pilocarpine in rats: investigation of the putative role of hippocampal pathways.

RATIONALE: Behavioral consequences of convulsive episodes are well documented, but less attention was paid to changes that occur in response to subconvulsant doses of drugs. OBJECTIVES: We investigated short- and long-term effects of a single systemic injection of a subconvulsant dose of pilocarpine on the behavior of rats as evaluated in the elevated plus maze. METHODS AND RESULTS: Pilocarpine induced an anxiogenic-like profile 24 h later, and this effect persisted for up to 3 months (% of time spent on open arms at 24 h, control = 35.47 ± 3.23; pilocarpine 150 = 8.2 ± 2.6; 3 months, control = 31.9 ± 5.5; pilocarpine 150 = 9.3 ± 4.9). Temporary inactivation of fimbria-fornix with lidocaine 4% promoted an anxiolytic-like effect per se, suggesting a tonic control of this pathway on the modulation of anxiety-related behaviors. Lidocaine also reduced the anxiogenic-like profile of animals tested 1 month after pilocarpine treatment (% of time spent on open arms, saline + phosphate-buffered saline (PBS) = 31.7 + 3.7; saline + lidocaine = 54.4 + 4.7; pilocarpine + PBS = 10.3 + 4.1; pilocarpine + lidocaine = 40.1 + 9.1). To determine whether the anxiogenic-like effect was mediated by septal region or by direct hippocampal projections to the diencephalon, the neural transmission of post-commissural fornix was blocked, and a similar reduction in the anxiogenic-like effect of pilocarpine was observed. CONCLUSIONS: Our findings suggest that a single systemic injection of pilocarpine may induce long-lasting anxiogenic-like behavior in rats, an effect that appears to be mediated, in part, through a direct path from hippocampus to medial hypothalamic sites involved in fear responses.

Role of the macrophage inflammatory protein-1alpha/CC chemokine receptor 5 signaling pathway in the neuroinflammatory response and cognitive deficits induced by beta-amyloid peptide.

The hallmarks of Alzheimer's disease include the deposition of beta-amyloid (Abeta), neuroinflammation, and cognitive deficits. The accumulation of activated glial cells in cognitive-related areas is critical for these alterations, although little is known about the mechanisms driving this event. Herein we used macrophage inflammatory protein-1alpha (MIP-1alpha(-/-))- or CC-chemokine receptor 5 (CCR5(-/-))-deficient mice to address the role played by chemokines in molecular and behavioral alterations induced by Abeta(1-40). Abeta(1-40) induced a time-dependent increase of MIP-1alpha mRNA followed by accumulation of activated glial cells in the hippocampus of wild-type mice. MIP-1alpha(-/-) and CCR5(-/-) mice displayed reduced astrocytosis and microgliosis in the hippocampus after Abeta(1-40) administration that was associated with decreased expression of cyclooxygenase-2 and inducible nitric oxide synthase, as well as reduced activation of nuclear factor-kappaB, activator protein-1 and cyclic AMP response element-binding protein. Furthermore, MIP-1alpha(-/-) and CCR5(-/-) macrophages showed impaired chemotaxis in vitro, although cytokine production in response to Abeta(1-40) was unaffected. Notably, the cognitive deficits and synaptic dysfunction induced by Abeta(1-40) were also attenuated in MIP-1alpha(-/-) and CCR5(-/-) mice. Collectively, these results indicate that the MIP-1alpha/CCR5 signaling pathway is critical for the accumulation of activated glial cells in the hippocampus and, therefore, for the inflammation and cognitive failure induced by Abeta(1-40). Our data suggest MIP-1alpha and CCR5 as potential therapeutic targets for Alzheimer's disease treatment.

Anticonvulsant and anxiolytic-like effects of compounds isolated from Polygala sabulosa (Polygalaceae) in rodents: in vitro and in vivo interactions with benzodiazepine binding sites.

RATIONALE: Polygala sabulosa, a folk medicine, presents dihydrostyryl-2-pyrones (DST) and styryl-2-pyrones (STY), compounds structurally similar to kavalactones. Our previous study showed that the ethyl acetate fraction (EA) and these constituents present anxiolytic-like, hypno-sedative, and anticonvulsant effects in mice. OBJECTIVES: This study investigated the role of benzodiazepine binding site (BDZ-bs) in the central effects of either EA or three DST (1, 2, and 3) and three STY (4, 5, and 7), using in vivo and in vitro assays. METHODS AND RESULTS: In the elevated plus-maze (EPM), flumazenil (FMZ), a BDZ antagonist, partially blocked the anxiolytic-like effect of DST-3 or STY-4 and STY-7, but not DST-1. Using electroencephalogram (EEG), EA protected against pentylenetetrazole (PTZ)-induced convulsion in rats, an effect partially blocked by FMZ, suggesting the participation of the BDZ-bs in this action. EA also protected against the maximal electroshock (MES)-induced convulsions in mice, a profile distinct from diazepam (DZP). DST and STY compounds inhibited the [(3)H]-flunitrazepam ([(3)H]-FNZ) binding to BDZ-bs in rat cortical synaptosomes with K (i) higher than 100 microM (DST-1), 41.7 microM (DST-2), 35.8 microM (DST-3), 90.3 microM (STY-4), 31.0 microM (STY-5) and 70.0 microM (STY-7). In the saturation assay, DST-3 and STY-7 competitively inhibited the binding of [(3)H]-FNZ to BDZ-bs with a significant decrease in apparent affinity (K (d)) and no change in maximal binding (B (max)). CONCLUSIONS: The present data support a partial BDZ-bs mediation of the anxiolytic-like and anticonvulsant effects of EA of P. sabulosa and its main isolated constituents, DST and STY.

Evidence for the involvement of the monoaminergic system in the antidepressant-like action of two 4-amine derivatives of 10,11-dihydro-5H-dibenzo [a,d] cycloheptane in mice evaluated in the tail suspension test.

Our previous study described the synthesis of 4-amine derivatives of 10,11-dihydro-5H-dibenzo-alkylamine-cycloheptane, 4-amine (3-N,N-dimethylpropylamine)-10,11-dihydro-5H-dibenzo[a,d] cycloheptane-5-one (ADDCH1), and 1,2,3,4,8,9-hexahydro-dibenzocycloheptane[4,4a,5-ef]1,4-diazepin (ADDCH2), and the characterization of their antidepressant-like effect in the forced swimming test in mice. This study investigated the involvement of monoaminergic pathways in the antidepressant-like effect of these compounds in mice evaluated in the tail suspension test (TST), another animal model to screen antidepressant drugs. Our results show that the immobility time in the TST was significantly reduced by ADDCH1 (15 to 50 mg/kg, i.p.) or ADDCH2 (30 and 50 mg/kg, i.p.). The antidepressant-like effect of ADDCH1 (30 mg/kg, i.p.) in the TST was prevented by pre-treatment of mice with methysergide (2 mg/kg, i.p.), a non-selective serotonin receptor antagonist, p-chlorophenylalanine methylester (pCPA, 100 mg/kg, i.p.), an inhibitor of serotonin synthesis, prazosin (62.5 microg/kg, i.p.), an alpha1-adrenoceptor antagonist, or yohimbine (1 mg/kg, i.p.), an alpha2-adrenoceptor antagonist. In contrast, the antidepressant-like effect of ADDCH2 was antagonized only by yohimbine (1 mg/kg) or haloperidol (50 microg/kg, i.p.), a dopamine D2/D3/D4 receptor antagonist, and was not affected by methysergide, pCPA or prazosin. Altogether, the present results strongly suggest the differential involvement of monoaminergic systems, serotonin/noradrenaline (ADDCH1) and noradrenaline/dopamine (ADDCH2) pathways, respectively, in the antidepressant-like effect of dibenzosuberone compounds.

Participation of dihydrostyryl-2-pyrones and styryl-2-pyrones in the central effects of Polygala sabulosa (Polygalaceae), a folk medicine topical anesthetic.

This study was undertaken to evaluate the psychopharmacological effects in mice of the hydroethanolic extract (HE), aqueous, hexane and ethyl acetate (EA) fractions, and 6-methoxy-7-prenyloxycoumarin, three dihydrostyryl-2-pyrones and three styryl-2-pyrones isolated from Polygala sabulosa (Polygalaceae), a folk medicine used as a topical anesthetic. In the elevated plus-maze test (EPM), the HE of P. sabulosa and its EA induced an increase in the percentage of time spent on, and in the frequency of entries into the open arms, as well as in the number of unprotected head-dipping, besides a reduction in protected stretch-attend postures, thus indicating an anxiolytic-like profile of action for this plant species. In the hypnosis test, HE and EA enhanced the duration of pentobarbital-induced sleep, a hypnosedative effect confirmed in ethyl ether-induced hypnosis. Moreover, both preparations reduced the duration of the first convulsion induced by pentylenetetrazol, besides decreasing the severity of the seizures. The dihydrostyryl-2-pyrones (1) and (3) as well as styryl-2-pyrones (4) and (7), centrally administered, showed a similar anxiolytic-like effect in the EPM test, while the dihydrostyryl-2-pyrone (2) and styryl-2-pyrone (5) were inactive at the doses used here. These results suggest that P. sabulosa is a herbal medicine which possesses anxiolytic-like, hypnosedative and anticonvulsant effects, and these central effects can be attributed to the presence of the dihydrostyryl-2-pyrone and styryl-2-pyrone compounds.

Antidepressant-like profile of action of two 4-amine derivatives of 10,11-dihydro-5H-dibenzo [a,d] cycloheptane in mice evaluated in the forced swimming test.

This study investigated the antidepressant-like effect of 4-amine derivatives of 10,11-dihydro-5H-dibenzo-alkylamine-cycloheptane, 4-amine (3-N,N-dimethylpropylamine)-10,11-dihydro-5H-dibenzo[a,d]cycloheptane-5-one (ADDCH1) and 1,2,3,4,8,9-hexahydro-dibenzocyclohepta[4,4a,5-ef]1,4-diazepin (ADDCH2), in a validated experimental model of depression, the forced swimming test (FST) in mice. Female adult mice were sub-chronically (three doses in 24 h) or repeatedly (once a day for 10 days) treated with either of the compounds and evaluated in the FST. The sub-chronic treatment promoted a dose-dependent reduction in the immobility time in the FST with the doses of 50 mg/kg (ADDCH1) and 30 mg/kg (ADDCH2) ip being the most effective (33% and 37% of reduction, respectively). A similar profile of action was observed in the animals repeatedly treated with ADDCH1 50 mg/kg or ADDCH2 30 mg/kg ip (for 10 days) and there was no sign of motor impairment or locomotor activation as evaluated in the rota-rod and open-field tests, respectively. These findings suggest that these amine derivatives of the system dibenzocycloheptane have an antidepressant-like action which could be of clinical interest and, therefore, deserves further investigation. In addition, putative underlying mechanisms of action are discussed.

Antidepressant-like effect of Ro5-4864, a peripheral-type benzodiazepine receptor ligand, in forced swimming test.

This study examined the effects of peripheral-type benzodiazepine receptors in the forced swimming test. PK 11195 (1-(2-chloro-phenyl)-N-methyl-N-(1-methylpropyl)-1-isoquinoline carboxamide) and Ro5-4864 (7-chloro-5-(4-chlorophenyl)-1,3-dihydro-1-methyl-2H-1,4-benzodiazepine-2-one) were i.p. injected in mice, according to an acute (1 or 24 h) and a repeated (14 days) schedule. Pretreatment with the agonist, Ro5-4864, significantly reduced immobility time 1 h after treatment but not 24 h after it, whereas the antagonist, PK11195, did not interfere with the test parameters. Nevertheless, PK11195 pretreatment inhibited the Ro5-4864 antidepressant-like effect. Animals repeatedly treated with Ro5-4864 had a similar profile of action with no sign of motor impairment or locomotor activation as evaluated in the rota-rod and open-field tests, respectively. Aminoglutethimide pretreatment, which blocks the early step of steroid synthesis, inhibited the antidepressant-like effect of Ro5-4864. The present findings suggest an antidepressant-like profile for the benzodiazepine, Ro5-4864, that seems to involve steroid synthesis as underlying mechanism.