Wet Dog Shakes Research Articles

Tolerance to neurochemical and behavioral effects of the hallucinogen 25I-NBOMe

Rationale4-Iodo-2,5-dimethoxy-N-(2-methoxybenzyl)phenethylamine (25I-NBOMe) is a potent serotonin 5-HT2A/2C receptor agonist with hallucinogenic activity. There is no data on the 25I-NBOMe effect on brain neurotransmission and animal performance after chronic administration.ObjectivesWe examined the effect of a 7-day treatment with 25I-NBOMe (0.3 mg/kg/day) on neurotransmitters’ release and rats’ behavior in comparison to acute dose.MethodsChanges in dopamine (DA), serotonin (5-HT), acetylcholine (ACh), and glutamate release were studied using microdialysis in freely moving rats. The hallucinogenic activity was measured in the wet dog shake (WDS) test. The animal locomotion was examined in the open field (OF) test, short-term memory in the novel object recognition (NOR) test. The anxiogenic/anxiolytic properties of the drug were tested using the light/dark box (LDB) test.ResultsRepeated administration of 25I-NBOMe decreased the response to a challenge dose of DA, 5-HT, and glutamatergic neurons in the frontal cortex as well as weakened the hallucinogenic activity in comparison to acute dose. In contrast, striatal and accumbal DA and 5-HT release and accumbal but not striatal glutamate release in response to the challenge dose of 25I-NBOMe was increased in comparison to acute treatment. The ACh release was increased in all brain regions. Behavioral tests showed a motor activity reduction and memory deficiency in comparison to a single dose and induction of anxiety after the drug’s chronic and acute administration.ConclusionsOur findings suggest that multiple injections of 25I-NBOMe induce tolerance to hallucinogenic activity and produce alterations in neurotransmission. 25I-NBOMe effect on short-term memory, locomotor function, and anxiety seems to be the result of complex interactions between neurotransmitter pathways.

Effects of valsartan on morphine tolerance and dependence in rats.

Background and purpose:Opiates are traditionally used for the treatment of pain. Chronic consumption of opiates such as morphine (MOR) induces tolerance and dependence. This study aimed to investigate the effects of valsartan (VAL), as an angiotensin II receptor blocker, on the induction and expression of MOR analgesic tolerance and physical dependence in rats.Experimental approach:MOR 10 mg/kg was injected s.c. twice a day for 7 days to induce tolerance and dependence. For evaluating the effect of VAL on the induction of MOR analgesic tolerance and physical dependence, 20 mg/kg VAL was administered orally (once a day) during the 7 days of the examination period. The tail-flick test was performed every day. On day 7, 5 mg/kg naloxone () was injected s.c. into the morphine-dependent rats and the rats were monitored for 30 min for the frequency of withdrawal signs such as jumping, diarrhea, defecation, head tremor, rearing, scratching, sniffing, teeth chattering, and wet-dog shake. For evaluating the effect of VAL on the expression of MOR-analgesic tolerance and physical dependence, 45 min before the last MOR injection, VAL was administered only on day 7. The tail-flick test was performed and naloxone was injected into the addicted rats and they were monitored for 30 min for the frequency of withdrawal signs such as jumping, diarrhea, defecation, head tremor, rearing, scratching, sniffing, teeth chattering, and wet-dog shake.Findings/Results:Our results revealed that the co-administration of VAL with MOR for 7 consecutive days reduced the induction of MOR tolerance. Moreover, VAL administration for 7 days along with MOR reduced the frequency of diarrhea and defecation in naloxone-injected animals.Conclusion and implications:According to the results presented in this study, chronic administration of VAL prevented the induction of MOR-analgesic tolerance and dependence in rats.

A novel rodent accelerometer device for measuring locomotor activity and other movements

Locomotor activity is a simple, yet useful measure of drug-induced changes in rodent behavior. Current methods for assessing activity often fail to capture more complex behavioral topographies, such as stereotypy, require measuring movement in novel environments, and/or require invasive surgeries. Here, we describe a novel device that wirelessly transmits fine motor behaviors at high frequencies. An accelerometer (Biosense, Palo Alto, CA) encased in a plastic covering (2 cm × 1 cm × 0.5 cm) is adhered to the skin between the scapula of a rodent. The device records changes in acceleration (m/s2) and converts it to frequency (Hz) using a Fourier transform. Data is collected about 50,000 times per 10 minutes and is sent to a computer via WiFi. Once new data is uploaded to the cloud (Google Cloud), a system processes the raw accelerometer values and quantifies certain types of activity using proprietary Python code. The processed data is accessible via an online web portal. To compare this novel approach with established methods, male Sprague Dawley rats were habituated to a novel acrylic cage (14” × 14” × 8”) for 90 minutes then were treated with amphetamine (0, 0.32, 1.0, 3.2 mg/kg subcutaneous, n=8 per dose). Locomotor activity was recorded using infrared beam breaks (Columbus Instruments, Columbus, OH) and the accelerometers simultaneously in the same rats. Amphetamine dose-dependently increased locomotor activity in both measures for approximately 2.5 hours, with the magnitude and duration of the effect being closely correlated between the two measures. Further, only the accelerometers were able to identify and quantify stereotyped movements and other behaviors, such as walking, running, or wet-dog shakes. In addition to locomotor activity, the devices were able to detect pentylenetetrazole-induced convulsion related movements (56 mg/kg subcutaneous, n=6) and increased activity during the dark cycle as compared with light cycle in the home cage (n=8). This novel method for recording rodent activity will be a useful approach for capturing and quantifying complex drug-induced behaviors as well as changes in circadian behavior in known and novel environments.

Identification of N-acyl-N-indanyl-α-phenylglycinamides as selective TRPM8 antagonists designed to mitigate the risk of adverse effects

Transient receptor potential melastatin 8 (TRPM8), a temperature-sensitive ion channel responsible for detecting cold, is an attractive molecular target for the treatment of pain and other disorders. We have previously discovered a selective TRPM8 antagonist, KPR-2579, which inhibited bladder afferent hyperactivity induced by acetic acid instillation into the bladder. However, additional studies have revealed potential adverse effects with KPR-2579, such as the formation of a reactive metabolite, CYP3A4 induction, and convulsions. In this report, we describe the optimization of α-phenylglycinamide derivatives to mitigate the risk of these adverse effects. The optimal compound 13x exhibited potent inhibition against icilin-induced wet-dog shakes and cold-induced frequent voiding in rats, with a wide safety margin against the potential side effects.

Contribution of serotonin receptor subtypes to hallucinogenic activity of 25I-NBOMe and to its effect on neurotransmission

Background4-Iodo-2,5-dimethoxy-N-(2-methoxybenzyl)phenethylamine (25I-NBOMe) is a potent serotonin (5-HT) receptor agonist with hallucinogenic properties. The aim of our research was to examine the role of the 5-HT2A, 5-HT2C and 5-HT1A serotonin receptor subtypes in 25I-NBOMe hallucinogenic activity and its effect on dopamine (DA), 5-HT and glutamate release in the rat frontal cortex.MethodsHallucinogenic activity was investigated using the wet dog shake (WDS) test. The release of DA, 5-HT and glutamate in the rat frontal cortex was studied using a microdialysis in freely moving rats. Neurotransmitter levels were analyzed by HPLC with electrochemical detection. The selective antagonists of the 5-HT2A, 5-HT2C and 5-HT1A serotonin receptor subtypes: M100907, SB242084 and WAY100635, respectively were applied through a microdialysis probe.ResultsThe WDS response to 25I-NBOMe (1 and 3 mg/kg) was significantly reduced by local administration of M100907 and SB242084 (100 nM). The 25I-NBOMe-induced increase in glutamate, DA and 5-HT release was inhibited by M100907 and SB242084. WAY100635 had no effect on 25I-NBOMe-induced WDS and glutamate release, while it decreased DA and 5-HT release from cortical neuronal terminals.ConclusionThe obtained results suggest that 5-HT2A and 5-HT2C receptors play a role in 25I-NBOMe-induced hallucinogenic activity and in glutamate, DA and 5-HT release in the rat frontal cortex as their respective antagonists attenuated the effect of this hallucinogen. The disinhibition of GABA cells by the 5-HT1A receptor antagonist seems to underlie the mechanism of decreased DA and 5-HT release from neuronal terminals in the frontal cortex.

Peptide Mimetic of BDNF Loop 4 Blocks Behavioral Signs of Morphine Withdrawal Syndrome and Prevents the Increase in ΔFosB Level in the Striatum of Rats.

Activity of compound GSB-106, a low-molecular mimetic of loop 4 of the brain neurotrophic factor (BDNF), was studied in experimental morphine withdrawal syndrome simulated in outbred rats. Single and subchronic (5 intraperitoneal injections) administration of GSB-106 in a dose of 0.1 mg/kg significantly reduced the total index of morphine withdrawal syndrome by 55.2 and 45.6%, respectively. GSB-106 reduced the severity of some behavioral signs (piloerection, gnashing of teeth, wet-dog shaking, and runaway attempts), but had no effect on mechanical allodynia formed in the rats with dependence. Subchronic treatment with GSB-106 prevented the increase in the content of ΔFosB (product of early response gene) in the striatum induced by morphine withdrawal. The results confirmed the concept on the involvement of neurotrophins, specifically BDNF and its analogs, in the mechanisms associated with the formation of opiate dependence.

TNF-α suppresses SHOX2 expression via NF-κB signaling pathway and promotes intervertebral disc degeneration and related pain in a rat model.

This study was conducted to verify the relative expression patterns of SHOX2 and its regulation by tumor necrosis factor alpha (TNF-α) during the development of intervertebral disc degeneration (IVDD). A rat disc-degeneration model was subjected to disc puncture (DP) and intradiscal injections with TNF-α to determine the roles of TNF-α and SHOX2 expression in IVDD in vivo. TNF-α and SHOX2 expression patterns in different degenerative rat nucleus pulposus (NP) tissues were measured by immunohistochemistry (IHC). The effects of TNF-α on IVDD were determined by magnetic resonance imaging (MRI) and pain development of wet-dog shakes (WDS) were blinded assessment by pain-behavior testing, respectively. Changes in TNF-α on SHOX2 expression were measured by Western blot analysis and real-time reverse transcription polymerase chain reaction (RT-PCR). The roles of nuclear factor-κB (NF-κB) and mitogen-activated protein kinase (MAPK) in TNF-α-mediated SHOX2 activation were studied using viral transfection, Western blot analysis, and real-time RT-PCR. In vivo, TNF-α accelerated the process of IVDD and suppressed SHOX2 expression; compared to the DP group, WDS was significantly increased in TNF-α intradiscal injection group at 2 to 6 weeks after puncture (P < .05); In NP cells, TNF-α negatively affected the IVDD-associated SHOX2 suppression. While TNF-α promotes IVDD through activation of both MAPK and NF-κB signaling, it seemed that only NF-κB signaling controlled the TNF-α-mediated SHOX2 suppression that is associated with IVDD. The results of this study indicated that TNF-α inhibits SHOX2 expression and has promoted effects on IVDD in the rat model, and these effects might be associated with through NF-κB signaling pathway and promotes IVDD and related pain in a rat model.

Persistent effects of the orexin-1 receptor antagonist SB-334867 on naloxone precipitated morphine withdrawal symptoms and nociceptive behaviors in morphine dependent rats

Aim of the study In this study, we investigated the effect of long-term administration of orexin receptor 1 (OXR1) antagonist on naloxone-precipitated morphine withdrawal symptoms and nociceptive behaviors in morphine-dependent rats. Materials and methods Wistar rats received subcutaneous (s.c.) injections of morphine (6, 16, 26, 36, 46, 56, and 66 mg/kg, 2 ml/kg) at an interval of 24 h for 7 days. In chronic groups, the OXR1 antagonist, SB-334867 (20 mg/kg, i.p.), or its vehicle, was injected repetitively from postnatal day 1 (PND1)-PND23 and then for the following seven days before each morphine injection. Meanwhile, in acute groups, SB-334867, or its vehicle, was administered before each morphine injection. In groups of rats that were designated for withdrawal experiments, naloxone (2.5 mg/kg, i.p.) was administered after the last injection of morphine. In the formalin-induced pain, the effect of OXR1 inhibition on the antinociceptive effects of morphine was measured by injecting formalin after the final morphine injection. Results Animals that received long-term SB-334867 administration before morphine injection demonstrated a significant reduction in chewing, defecation, diarrhea, grooming, teeth chattering, wet-dog shake, and writhing. Inhibiting OXR1 for a long time increased formalin-induced nociceptive behaviors in interphase and phase II of the formalin-induced pain. Conclusions Our results indicated that the inhibition of OXR1 significantly reduces the development of morphine dependence and behavioral signs elicited by the administration of naloxone in morphine-dependent rats. Furthermore, the prolonged blockade of OXR1 might be involved in formalin-induced nociceptive behaviors.

The effects of morphine withdrawal and conditioned withdrawal on memory consolidation and c-Fos expression in the central amygdala.

The current study tested the hypothesis that drug withdrawal contributes to the addiction cycle in part because of an action on memory consolidation. Hence, four experiments in male Sprague-Dawley rats compared the effects of precipitated morphine withdrawal and conditioned morphine withdrawal on the consolidation of object memory and on activation of c-Fos in the central nucleus of the amygdala (CeA). It was found that immediate, but not 6 h delayed, post sample administration of 3 mg/kg of naltrexone significantly enhanced object memory in rats maintained, or previously maintained, on 10 mg/kg/day of morphine via osmotic minipumps. To establish whether conditioned withdrawal could also alter object memory, a contextual conditioning procedure was employed whereby morphine-maintained (10 mg/kg/day) animals received naltrexone (3 mg/kg) in a distinctive context (CS+) and vehicle in a separate context (CS-) for 10 days. During conditioning in the CS+, naltrexone suppressed locomotor activity, caused a rapid body weight loss and increased frequency of wet dog shakes. Interestingly, confinement to this CS+ immediately, but not 6 h, after the sample phase, also enhanced object memory. Finally, posttraining naltrexone and exposure to the CS+ both induced significant expression of c-Fos in the CeA. Therefore, this study reports for the first time that both acute precipitated withdrawal and conditioned withdrawal can facilitate memory consolidation, possibly through a common neural pathway that involves the central amygdala.

Behavioral assessment of rimonabant under acute and chronic conditions

Cannabinoid subtype 1 receptor (CB1R) antagonists were originally developed as anti-obesity agents. Unfortunately, SR1417116A (rimonabant), the first marketed inverse agonist of CB1R, produced CNS-related adverse effects including depression and suicidal ideation, and thus it was withdrawn from the market. These effects of rimonabant became evident in patients following chronic dosing. Standard preclinical toxicity studies failed to detect these adverse effects. The goal of these studies was to perform an integrated battery of behavioral assays to better understand the behavioral effects of rimonabant following both acute and chronic administration. In the present study, acute dosing with rimonabant in rats significantly decreased food consumption; decreased measures of locomotor activity; increased scratching, grooming and wet-dog shakes; and increased defecation. Subsequently, animals were tested using a chronic dosing regimen but prior to drug administration for that day. The highest dose of rimonabant tested significantly decreased marble burying behavior, presumably anxiolysis. There were also significant effects in social interaction after chronic dosing. Our results did not reveal significant rimonabant-induced anxiogenic behaviors. Future studies to characterize behavioral screens for anxiogenic effects of CB1 antagonists in rodents should further explore social interaction paradigms and potential comorbid factors of rimonabant dosing such as sex, age, and obesity.

Effects of Compound 511 on BDNF-TrkB Signaling in the Mice Ventral Tegmental Area in Morphine-Induced Conditioned Place Preference.

Compound 511 (511) is specially developed for opioid addiction treatment based on the Ancient Chinese drug rehabilitation literature, and its composition has profound effects in the treatment of drug addiction in various clinical trials and animal experiments. The effect of 511 on the rewarding properties of morphine and craving responses and its potential mechanisms remain unclear. Here, we have applied a conditioned place preference (CPP) paradigm in mice to measure morphine-induced rewarding effects under the treatment of 511. Then we used the RNA sequencing strategy to screen its potential mechanisms. In our research, firstly, we found 511 could decrease CPP score, locomotor activity, self-administration, jumping behavior, weight loss, wet-dog shakes, and stereotyped behavior. Then the brain VTA region tissues were performed mRNA sequencing to detect potential mechanisms. We found the brain-derived neurotrophic factor (BDNF) and tropomyosin-related kinase B (TrkB) were downregulated in morphine-induced CPP, whereas the decreased BDNF and TrkB were reversed after 511 treatment. We retested the levels of BDNF and TrkB using qRT-PCR and Western blot and found the similar results to mRNA sequencing. It has been widely reported that BDNF-TrkB signaling in the VTA is involved in multiple facets of addiction, including reward and motivation, so we focused on the BDNF-TrkB signaling to investigate the anti-addiction mechanisms of 511 in morphine addiction mice. We studied the downstream pathway of BDNF-TrkB and the soma size of dopaminergic neurons. The results showed 511 could increase the phosphorylation levels of PI3K and AKT, which were decreased in morphine-induced CPP. Simultaneously, 511 could decrease the level of PLCγ1 and the phosphorylation levels of ERK and S6K, which were increased in morphine-induced CPP. In addition, 511 also enlarged the soma size of VTA dopaminergic neurons, which was reduced in morphine-induced CPP. Hence, our research indicated 511 maybe mediate the BDNF-TrkB signaling in VTA to improve morphine addiction behavior.

Tb1, a Neurotoxin from Tityus bahiensis Scorpion Venom, Induces Epileptic Seizures by Increasing Glutamate Release.

Here, we report the neurotoxic effects aroused by the intracerebral injection (in rats) of Tb1, which is a neurotoxin isolated from Tityus bahiensis scorpion venom. Biochemical analyses have demonstrated that this toxin is similar to the gamma toxin from T. serrulatus, which is a β-scorpion toxin that acts on sodium channels, causing the activation process to occur at more hyperpolarized membrane voltages. Male Wistar rats were stereotaxically implanted with intrahippocampal electrodes and cannulas for electroencephalographic recording and the evaluation of amino acid neurotransmitters levels. Treated animals displayed behavioral and electroencephalographic alterations similar to epileptiform activities, such as myoclonus, wet dog shakes, convulsion, strong discharges, neuronal loss, and increased intracerebral levels of glutamate. Scorpion toxins are important pharmacological tools that are widely employed in ion channel dysregulation studies. The current work contributes to the understanding of channelopathies, particularly epilepsy, which may originate, among other events, from dysfunctional sodium channels, which are the main target of the Tb1 toxin.

Silver nanoparticles (Ag-NPs) in the central amygdala protect the rat conditioned by morphine from withdrawal attack due to naloxone via high-level nitric oxide.

Repeated injection of morphine during conditioned place preference (CPP) leads to spatial craving due to high-level nitric oxide (NO) in the central nucleus of amygdala (CeA). Silver nanoparticles (Ag-NPs) can produce oxygen-free radicals that lead to NO formation. We aimed to show the Ag-NPs protective effect on naloxone (NLX)-induced morphine withdrawal in the conditioned rats. Wistar rats (300-350g) were implanted with cannulae in the CeA. After recovery, they were randomly divided into experimental and saline groups. CPP was conducted by three-phase unbiased program. Morphine (0.5-7.5mg/kg) was injected subcutaneously (s.c.) once/per day during the conditioning phase. Naloxone (NLX) (0.05-0.4μg/rat) was given, intra-CeA, 10min before the CPP test. Ag-NPs (0.0001-0.01μg/rat) were administered alone or prior to the NLX effective dose (0.4μg/rat), intra-CeA. Conditioning score and withdrawal signs (wet dog shaking and scratching) were obtained and compared with saline group data. All rats' brains were collected in formalin 10% and after 48-72h stained with NADPH-diaphorase, the NO marker. All data were analyzed by one-way or two-way ANOVA. Morphine (2.5-7.5mg/kg, s.c.) induced a significant CPP vs. saline (1mL/kg, s.c.). The single Ag-NPs had no significant effect, whereas the NLX caused meaningful WDS and scratching. However, the NLX pre-treatment in combination with Ag-NPs eliminated these signs. Furthermore, the NO level increased in the CeA. The Ag-NPs may protect the morphine-conditioned rats against the NLX-induced withdrawal symptoms due to high-level NO in the CeA.

Cinnamaldehyde elicits itch behavior via TRPV1 and TRPV4 but not TRPA1.

Introduction:Cinnamaldehyde (CA) elicits itch sensation in humans. We investigated if CA elicits scratching behavior in mice and determined the roles for TRPV1, TRPA1, and TRPV4.Materials and Methods:Scratching behavior elicited by intradermal injection of CA was assessed in wildtype (WT) mice and knockout (KO) mice lacking TRPV1, TRPA1, TRPV4, or deficient in mast cells. We also assessed scratching and wet dog shakes elicited by low-threshold mechanical stimulation of skin treated topically with CA or vehicle. Using calcium imaging we tested if CA activates dorsal root ganglion (DRG) neurons of each genotype.Results:Intradermal cheek injection of CA elicited dose-dependent hindlimb scratch bouts, with fewer forelimb wipes and facial groom bouts that were not dose-dependent. CA elicited significantly fewer scratch bouts in TRPV1 and TRPV4 KO mice, but not TRPA1KOs, compared with WTs. There were no sex differences across genotypes. The histamine H1 antagonist cetirizine did not affect CA-evoked scratching, which was normal in mast cell deficient mice, indicating lack of histamine involvement. Scores for alloknesis were significantly greater following topical application of CA compared with vehicle. Post-CA alloknesis scores were significantly higher in TRPV4KOs of both sexes and in female TRPV1 and TRPA1KOs, compared with WTs. Low threshold mechanical stimuli also elicited significantly more wet dog shakes in mice treated topically with 20% CA, with significantly fewer in TRPV1, TRPA1, and TRPV4KOs compared with WTs. In calcium imaging studies, CA excited 24% of WT DRG cells, significantly fewer (11.5%) in cells from TRPV4KOs, and none in TRPA1KOs. Responses of cells of all genotypes exhibited significant sensitization to repeated CA stimulation. Sensitization was significantly enhanced by IL-4, which itself excited 16% of WT DRG cells and none from TRPA1KOs.Discussion:The results indicate that TRPA1 is dispensable for CA-evoked scratching, which depends partly on TRPV1 and TRPV4.

Structure-Based Design of Novel Biphenyl Amide Antagonists of Human Transient Receptor Potential Cation Channel Subfamily M Member 8 Channels with Potential Implications in the Treatment of Sensory Neuropathies.

Structure-activity relationship studies of a reported menthol-based transient receptor potential cation channel subfamily M member 8 channel (TRPM8) antagonist, guided by computational simulations and structure-based design, uncovers a novel series of TRPM8 antagonists with >10-fold selectivity versus related TRP subtypes. Spiro[4.5]decan-8-yl analogue 14 inhibits icilin-evoked Ca2+ entry in HEK-293 cells stably expressing human TRPM8 (hTRPM8) with an IC50 of 2.4 ± 1.0 nM, while in whole-cell patch-clamp recordings this analogue inhibits menthol-evoked currents with a hTRPM8 IC50 of 64 ± 2 nM. Molecular dynamics (MD) simulations of compound 14 in our homology model of hTRPM8 suggest that this antagonist forms extensive hydrophobic contacts within the orthosteric site. In the wet dog shakes (WDS) assay, compound 14 dose-dependently blocks icilin-triggered shaking behaviors in mice. Upon local administration, compound 14 dose dependently inhibits cold allodynia evoked by the chemotherapy oxaliplatin in a murine model of peripheral neuropathy at microgram doses. Our findings suggest that 14 and other biphenyl amide analogues within our series can find utility as potent antagonist chemical probes derived from (-)-menthol as well as small molecule therapeutic scaffolds for chemotherapy-induced peripheral neuropathy (CIPN) and other sensory neuropathies.

Characterization of New TRPM8 Modulators in Pain Perception.

Background: Transient Receptor Potential Melastatin-8 (TRPM8) is a non-selective cation channel activated by cold temperature and by cooling agents. Several studies have proved that this channel is involved in pain perception. Although some studies indicate that TRPM8 inhibition is necessary to reduce acute and chronic pain, it is also reported that TRPM8 activation produces analgesia. These conflicting results could be explained by extracellular Ca2+-dependent desensitization that is induced by an excessive activation. Likely, this effect is due to phosphatidylinositol 4,5-bisphosphate (PIP2) depletion that leads to modification of TRPM8 channel activity, shifting voltage dependence towards more positive potentials. This phenomenon needs further evaluation and confirmation that would allow us to understand better the role of this channel and to develop new therapeutic strategies for controlling pain. Experimental approach: To understand the role of TRPM8 in pain perception, we tested two specific TRPM8-modulating compounds, an antagonist (IGM-18) and an agonist (IGM-5), in either acute or chronic animal pain models using male Sprague-Dawley rats or CD1 mice, after systemic or topical routes of administration. Results: IGM-18 and IGM-5 were fully characterized in vivo. The wet-dog shake test and the body temperature measurements highlighted the antagonist activity of IGM-18 on TRPM8 channels. Moreover, IGM-18 exerted an analgesic effect on formalin-induced orofacial pain and chronic constriction injury-induced neuropathic pain, demonstrating the involvement of TRPM8 channels in these two pain models. Finally, the results were consistent with TRPM8 downregulation by agonist IGM-5, due to its excessive activation. Conclusions: TRPM8 channels are strongly involved in pain modulation, and their selective antagonist is able to reduce both acute and chronic pain.

Anticonvulsive and neuroprotective effects of aqueous and methanolic extracts of Anacyclus pyrethrum root in kainic acid-induced-status epilepticus in mice

PurposeEpilepsy is a chronic neurological disorder characterized by spontaneous and recurrent seizures. The currently available synthetic antiepileptic drugs have a limited efficacy and are associated with a wide range of side effects. In Ayurveda, Anacyclus pyrethrum root (APR) has been used as a traditional antiepileptic remedy. The aim of the present study is to evaluate the anticonvulsive and neuroprotective effects of aqueous and methanol extracts of Anacyclus pyrethrum root (AEAPR and MEAPR) on experimental model of status epilepticus (SE). MethodsTwenty four male mice were divided into four groups. The control and KA groups had free access to tap water for 5 days before the intraperitoneal injection of distillated water or kainic acid (KA; 30 mg/kg), respectively. In the treated groups, mice received extracts solutions MEAPR and AEAPR in drinking water at the concentration of 5 g/l for 5 days. At the fifth day, animals received intraperitoneal injection of KA. The behavioral changes latency of seizures, the number of wet dog shakes (WDS) and the mortality were observed over 6 h. Thereafter, the mice were sacrificed for immunohistochemical studies. ResultsPretreatment with MEAPR and AEAPR decreases significantly the frequency of WDS (32.5% and 43.9%, p < 0.01; respectively), and increases considerably the latent period (77.9% and 91.9%, p<0.01; respectively) between the injection of the KA and the appearance of the SE as compared to the KA group. The duration and severity of seizure in the MEAPR or AEAPR-pretreated groups were significantly lower (p < 0.01 and p < 0.05 or p < 0.01; respectively) than those in the KA group. These behavioral results were confirmed by the immunohistochemical study at the level of the hippocampus, in which the c-FOS and GFAP expression of both MEAPR and AEAPR-treated animals largely reduced (p < 0.001) the number of labelled cells with respect to the group, which received the KA alone. ConclusionOur results showed that the MEAPR and AEAPR have anticonvulsive effect and putative neuroprotective effect against seizures induced by KA. Further studies are required to identify its active ingredients responsible for the observed effects.

The role of Smyrnium cordifolium Boiss extract and curzerene on withdrawal syndrome in mice

Morphine is the most effective medication to relieve pain, antinociception and withdrawal syndrome, but clinical application of these compounds is greatly affected by the occurrence of addiction. The aim of this research was the influence of SE and curzerene (Cur) on withdrawal syndrome signs in mice contrasted with clonidine. Extraction of the S. cordifolium extract (SE) was done by the Soxhlet method. Addiction was produced using the subcutaneous injections of morphine for 7 days. To estimate the influences of SE and Cur, the 64 male mice were separated into eight of 8. Sets 1, 2 and 3 were treated SE (100,200,300 mg/kg). Sets 4, 5 and 6 were treated Cur (0.03, 0.06, 0.12mg/kg). The findings showed that curzerene was the most important effective component S. cordifolium extract. Curzerene and SE reduced the mean of weight loss, diarrhea, and wet dog shakes in morphine-dependent mice in comparison with clonidine. All doses of Curzerene and SE extract reduced the locomotor activity and body weight loss when compared to the control group in morphine-dependent mice but not to clonidine compared. The SE (100mg/kg) and Cur (0.03mg/kg) are reduced signs of withdrawal syndrome equally to clonidine. SE (200 mg/kg) and Cur (0.06 mg/kg), are reduced of the body weight loss significantly in relation to clonidine (P&lt;0.05). SE (200 mg/kg) and Cur (0.06 mg/kg), are reduced of diarrhea significantly in relation to clonidine (P&lt;0.01). This was while SE (300mg/kg) and cur (0.12mg/kg) had deadly effect. Curzerene and SE are able to decrease the signs of withdrawal syndrome, which might have a human therapeutic capacity. Curzerene may be one of the terpenoids responsible for the effect of the S. cordifolium extract. Nevertheless, more investigations are needed to determine the exact mechanism of the effect of SE and curzerene.

Role of prefrontal cortical 5-HT2A receptors and serotonin transporter in the behavioral deficits in post-pubertal rats following neonatal lesion of the ventral hippocampus

Neonatal ventral hippocampal-lesioned (NVHL) rats have been shown to display neurochemical and behavioral abnormalities at adulthood, analogous to some of those seen in schizophrenia. Serotonergic neurotransmission is implicated the pathophysiology and treatment of schizophrenia. In this study, we evaluated possible role of serotonergic transmission is the behaviors of NVHL-lesioned rats. Bilateral lesions to the ventral hippocampus (VH) in rat pups were made using the excitotoxin ibotenic acid. We investigated 5-HT2A-receptor and SERT binding sites in cortical and subcortical areas in post-pubertal NVHL and sham-lesioned rats, using quantitative receptor autoradiography. We compared a 5-HT-dependent behavior in NVHL and sham animals, the wet-dog shake response (WDSr) to a 5-HT2A receptor agonist DOI. In addition, we studied prepulse inhibition (PPI) of startle responses in NVHL and Sham-lesioned animals treated with antipsychotic drugs haloperidol, risperidone and clozapine and 5-HT2A antagonists ketanserin or MDL100907. The WDSr elicited by DOI was enhanced in post-pubertal NVHL rats compared to sham-lesioned controls. Moreover, post-pubertal NVHL rats exhibited PPI deficits which was reversed by atypical antipsychotics, ketanserin and MDL100907. A significant increase in 5-HT2A-like receptor binding was observed in the medial prefrontal cortex (mPFC) in post-pubertal NVHL rats without any significant change in the striatum and ventral pallidum. A significant increase in SERT-like binding was also observed in the mPFC and striatum of NVHL rats at pre-pubertal period; however, at post-pubertal age, the binding remained elevated in mPFC only. These data suggest that increased prefrontal cortical 5-HT transmission may play a role in the behavioral deficits observed in this neurodevelopmental model of schizophrenia.

Endogenous opioid dependence after intermittent use of glucose, sodium chloride, and monosodium glutamate solutions.

In 2002, Colantuoni et al described the possibility of dependency in rats after intermittent, excessive consumption of a 25% glucose solution over a one‐week period. We hypothesized that the intermittent consumption of any tasty solution can lead to endogenous opioid dependency. Another aim was to determine whether dependency is connected to the taste of the consumed substance or with its physiological significance. Rats were maintained on chow and cyclic glucose, NaCl, or monosodium glutamate (MSG) solution for 8 days. On day 9, after a 12‐hr deprivation period and administration of intraperitoneally (IP) naloxone, the general withdrawal index was calculated as the sum of teeth chattering, head shaking, forepaw tremors, and wet dog shakes. Motor activity was also documented. After the intermittent consumption of any tasty solution, rats were found to demonstrate signs of endogenous opioid dependence. The development of dependence was not related to taste preferences or the amount of solution consumed. Intermittent use of essential substance with a pleasant taste, as glucose and sodium chloride, leads to the rapid development of endogenous opioid dependence. Withdrawal syndrome following the consumption of MSG solution is associated with the presence of sodium ions in the MSG molecule.