Laila Asth

The elevated T-maze task as an animal model to simultaneously investigate the effects of drugs on long-term memory and anxiety in mice.

The elevated T-maze (ETM) is an apparatus derived from the elevated plus-maze test, which is used to evaluate anxiety. Because anxiety is a biasing factor in models of memory, this study proposed the ETM as a task for the simultaneous assessment of memory and anxiety in mice. The ETM consists of one enclosed and two open arms. The procedure is based on the avoidance of open spaces learned during training session, in which mice were exposed to the enclosed arm as many times as needed to stay 300s. In the test session, memory is assessed by re-exposing the mouse to the enclosed arm and the latency to enter an open arm was recorded. The anxiolytic diazepam (DZP; 1 or 2mg/kg) and the amnestic biperiden (BPR; 0.5, 1 or 3mg/kg) were injected at three distinct times: pre-training, post-training, and pre-test. Pre-training administration of BPR 1 and DZP 2 increased the number of trials needed to reach the avoidance criterion, suggesting a passive avoidance learning impairment. However, BPR induced hyperlocomotion, which could bias the interpretation of any BPR-induced effects during the training session. Pre-training injection of BPR did not affect the spontaneous increase in the latency to enter an open arm between trials, while DZP reduced latencies in the first three trials suggesting anxiolysis. In the test session, pre-training injection of BPR 1 and DZP 2 reduced latencies to enter an open arm, indicating memory impairment. Post-training and pre-test injection of DZP or BPR did not affect memory. In conclusion, the proposed ETM task is practical for the detection of the anxiolytic and amnesic effects of drugs.

Blockade of nociceptin/orphanin FQ receptor signaling reverses LPS-induced depressive-like behavior in mice

Nociceptin/orphanin FQ is the natural ligand of a Gi-protein coupled receptor named NOP. This peptidergic system is involved in the regulation of mood states and inflammatory responses. The present study aimed to investigate the consequences of blocking NOP signaling in lipopolysaccharide (LPS)-induced sickness and depressive-like behaviors in mice. LPS 0.8mg/kg, ip, significantly induced sickness signs such as weight loss, decrease of water and food intake and depressive-like behavior in the tail suspension test. Nortriptyline (ip, 60min prior the test) reversed the LPS-induced depressive states. The NOP receptor antagonist SB-612111, 30min prior LPS, did not modify LPS-induced sickness signs and depressive-like behavior. However, when injected 24h after LPS, NOP antagonists (UFP-101, icv, and SB-612111, ip) significantly reversed the mood effects of LPS. LPS evoked similar sickness signs and significantly increased tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6) plasma levels 6h post-injection in wild-type ((NOP(+/+)) and NOP knockout ((NOP(-/-)) mice. However, LPS treatment elicited depressive-like effects in NOP(+/+) but not in NOP(-/-) mice. In conclusion, the pharmacological and genetic blockade of NOP signaling does not affect LPS evoked sickness signs while reversing depressive-like behavior.

Lithium and valproate prevent methylphenidate-induced mania-like behaviors in the hole board test

Manic bipolar is diagnosed by psychomotor agitation, increased goal-directed activity, insomnia, grandiosity, excessive speech, and risky behavior. Animal studies aimed to modeling mania are commonly based in psychostimulants-induced hyperlocomotion. The exploration of other behaviors related with mania is mandatory to investigate this phase of bipolar disorder in animals. In this study, the hole board apparatus was suggested for evaluating mania-like behaviors induced by the psychostimulant methylphenidate. The treatment with methylphenidate (10mg/kg, ip) increased locomotion in the open field test. The pretreatment with lithium (50mg/kg, ip) and valproate (400mg/kg, ip) significantly prevented the hyperlocomotion. In the hole-board test, methylphenidate increased interactions with the central and peripheral holes and the exploration of central areas. Lithium was more effective than valproate in preventing all the behavioral manifestations induced by the psychostimulant. These findings were discussed based on the ability of methylphenidate-treated mice mimicking two symptoms of mania in the hole board test: goal-directed action and risk-taking behavior. In conclusion, the results point to a new approach to study mania through the hole board apparatus. The hole board test appears to be a sensitive assay to detect the efficacy of antimanic drugs.

In vitro functional characterization of novel nociceptin/orphanin FQ receptor agonists in recombinant and native preparations.

Nociceptin/Orphanin FQ (N/OFQ) regulates several biological functions via selective activation of the N/OFQ receptor (NOP). In this study novel nonpeptide NOP ligands were characterized in vitro in receptor binding and [35S]GTPγS stimulated binding in membranes of cells expressing human NOP and classical opioid receptors, calcium mobilization assay in cells coexpressing the receptors and chimeric G proteins, bioluminescence resonance energy transfer (BRET) based assay for studying NOP receptor interaction with G protein and arrestin, the electrically stimulated mouse vas deferens and the mouse colon bioassays. The action of the AT compounds were compared with standard NOP agonists (N/OFQ and Ro 65-6570) and the NOP selective antagonist SB-612111. AT compounds displayed high NOP affinity and behaved as NOP agonists in all the functional assays consistently showing the following rank order of potency AT-127≥AT-090≥AT-035>AT-004= AT-001. AT compounds behaved as NOP full agonists in the calcium mobilization and mouse colon assays and as partial agonists in the [35S]GTPγS and BRET assays. Interestingly AT-090 and AT-127, contrary to standard nonpeptide agonists that display G protein biased agonism, behaved as an unbiased agonists. AT-090 and AT-127 displayed higher NOP selectivity than Ro 65-6570 at native mouse receptors. AT-090 and AT-127 might be useful pharmacological tools for investigating the therapeutic potential of NOP partial agonists.

Spontaneous failure of the estrous cycle induces anxiogenic-related behaviors in middle-aged female mice.

Clinical studies have shown that women during perimenopause and menopause have a higher incidence in the diagnoses of psychiatric problems compared with men. However, little literature information about the influence of spontaneous perimenopause on anxiety- and mood-related behaviors in mice is available. To this aim, we compared the behavioral responses of middle-aged and young adult female mice both in the diestrus phase in the elevated plus-maze, open field and forced swimming tests. In middle-aged mice, the duration of the estrous cycle was significantly prolonged compared to young adults, thus indicating that our middle-aged mice are in the perimenopausal period. In the elevated plus-maze test, middle-aged mice explored less the open arms when compared to young adults, suggesting an anxiogenic-like phenotype. No significant differences were observed in the estrogen plasma levels and emotional behavior in the forced swim and open field tests. In conclusion, the spontaneous failure of the estrous cycle increased anxiety in middle-aged females. These data suggest that the perimenopausal period has a significant influence on anxiety-related behaviors in female mice.

Central adenosine A1 and A2A receptors mediate the antinociceptive effects of neuropeptide S in the mouse formalin test

AIMS The present study aimed to investigate the intraplantar (ipl) and central (icv) effects of neuropeptide S (NPS) in the formalin test and to evaluate the role of adenosine receptors, mainly A1 and A2A, in mediating such effects. MAIN METHODS The ipl injection of formalin was used to assess the nociceptive activity. Moreover, by pretreating mice with non-selective and selective antagonists of adenosine receptors, the effects of icv NPS on formalin-induced ongoing nociception were assessed. KEY FINDINGS Morphine-induced antinociceptive effects were observed during phases 1 and 2 of the test, while indomethacin was active only at the later nociceptive phase. The ipl injection of NPS (alone or combined with formalin) did not modify the nociceptive response. However, icv NPS significantly reduced formalin-induced nociception during both phases. Caffeine (3 mg/kg, ip), a non-selective adenosine receptor antagonist, prevented NPS-induced antinociceptive effects. Similar to caffeine, icv ZM241385 (0.01 nmol), an A2A receptor antagonist, prevented the antinociceptive effects of NPS. Moreover, icv DPCPX (0.001 nmol), an A1 receptor antagonist, blocked the effects of NPS only during phase 1. SIGNIFICANCE The above findings suggest that: (i) NPS evokes central antinociceptive effects by activating both A1 and A2A receptors during phase 1, but (ii) only the adenosine A2A receptor during phase 2 of the formalin test.

Topiramate reduces basal anxiety and relieves ethanol withdrawal-induced anxious behaviors in male rats.

Anxiety disorders are associated with increased impairments in psychosocial functioning, work productivity and health-related quality of life. In addition, anxiety is a common symptom of ethanol withdrawal and it strongly contributes to relapse. Benzodiazepines are frequently prescribed for relief of anxiety and ethanol withdrawal symptoms but considerable side effects, such sedation, tolerance and dependence, are observed during treatment. Therefore, better drugs are needed for the treatment of anxiety states. The purpose of this study was to investigate whether topiramate would reduce basal levels of anxiety and ethanol-withdrawn induced anxiety in male rats; the elevated plus maze (EPM) was used as an animal model of anxiety. In Experiment 1, topiramate (0, 10, and 40 mg/kg, i.g.) and diazepam (1 mg/kg, i.p.) was acutely and repeatedly administered to naive rats. In Experiments 2 and 3, topiramate (0 or 40 mg/kg, i.g.) was acutely and chronically administered in early (72 hr after ethanol removal) and protracted (21 days after ethanol removal) ethanol-withdrawn rats, respectively. Acute and repeated topiramate treatment induced anxiolytic-like effects in naive rats. Early ethanol withdrawal increased anxiety, and acute topiramate administration counteracted the anxiogenic-like effects of ethanol removal. Protracted withdrawal did not produce lasting changes in anxiety but topiramate was equally effective at reducing anxiety in ethanol-withdrawn and control animals. Importantly, no signs of tolerance to the anxiolytic effects of topiramate were observed. In conclusion, these data support a role for topiramate in the treatment of basal levels of anxiety and ethanol withdrawal-induced anxiety.

Nociceptin/orphanin FQ receptor agonists increase aggressiveness in the mouse resident-intruder test

&NA; Aggressive behaviors can be considered symptoms of bipolar disorder, schizophrenia, post‐traumatic stress, intermittent explosive, and personality disorders. Nociceptin/orphanin FQ (N/OFQ) is a peptide acting as endogenous ligand of the NOP receptor. Preclinical and clinical findings suggest the NOP receptor as an innovative target for the treatment of psychopathologies, such as anxiety, depression, and drug abuse. This study investigated the effects of NOP ligands and the behavioral phenotype of mice lacking the NOP receptor in an animal model of aggressiveness, the resident‐intruder test. Mood stabilizers, such as valproate, lithium, and carbamazepine reduced aggressive behaviors of resident mice, while diazepam was inactive. In contrast, para‐chlorophenylalanine (PCPA), an inhibitor of 5‐HT synthesis, increased aggressiveness in mice. Similar to PCPA, the treatment with the NOP agonists Ro 65‐6570 and AT‐090 also increased aggressive behaviors. The systemic administration of the NOP antagonist SB‐612111 did not modify the behavior of resident mice, but it prevented the aggressive behavior of Ro 65‐6570. NOP receptor knockout mice did not display any behavioral difference compared to wild‐type animals in the resident‐intruder test. None of the treatments affected non‐agonistic behaviors and spontaneous locomotion. In conclusion, NOP receptor agonists increased aggressiveness, while the pharmacological and genetic blockade of NOP receptor signaling did not modify agonistic behaviors. Ultimately, the aggressive profile of action of NOP agonists should be taken into account in the development of innovative psychiatric drugs targeting the NOP receptor. HighlightsNOP agonists increased male mouse aggressiveness.The NOP antagonist SB‐612111 did not change mouse aggressiveness.NOP(‐/‐) mice did not display any behavioral phenotype in the resident‐intruder test.Lithium, valproate and carbamazepine attenuated mouse aggressiveness.An inhibitor of 5‐HT synthesis, PCPA, increased mouse aggressive behavior.

Monoaminergic neurotransmission is mediating the antidepressant-like effects of Passiflora edulis Sims fo. edulis

The genus Passiflora is popularly used to treat anxiety. Recent studies showed antidepressant-like effects of two varieties of P. edulis (edulis and flavicarpa) in mice. However, the mechanisms of antidepressant actions are still unknown. Here, the effects of P. edulis fo. edulis aqueous extract (AE, 100-300mg/kg, po), and ethyl acetate (AcOEt, 25-50mg/kg, po), butanol (BuOH, 25-50mg/kg, po) and residual aqueous (25-100mg/kg, po) fractions were investigated in the mouse forced swimming test. In addition, the involvement of monoamines in the P. edulis fractions-induced antidepressant actions was approached. HPLC analyses showed that AcOEt and BuOH, but not residual, fractions shared with AE the main peaks between 25 and 70min (UV 340nm), which are suggestive of flavonoids. Nortriptyline and fluoxetine reduced the immobility time and similar results were observed for AE, AcOEt and BuOH but not residual fractions. PCPA (inhibitor of 5-HT synthesis), AMPT (inhibitor of catecholamine synthesis) and sulpiride (selective D2 receptor antagonist), but not DSP-4 (noradrenergic neurotoxin), blocked the antidepressant actions of AcOEt and BuOH. In conclusion, AcOEt and BuOH fractions shared with AE similar phytochemical composition and antidepressant actions. Preserved 5-HT and dopamine transmissions were required for the antidepressant effects of P. edulis fractions.