Lamotrigine has an anxiolytic-like profile in the rat conditioned emotional response test of anxiety: a potential role for sodium channels?

Analysis of Anxiety Disorders and Post-Traumatic Stress Disorders for Screening Anxiolytic Drugs and Linking Preclinical and Clinical Research

How to determine suitable animal models of anxiety disorders and post-traumatic stress disorders (PTSD) for screening anxiolytic drugs and linking preclinical and clinical research is a crucial issue. This review paper provides background knowledge and critical determination to the animal models for discussing this issue. Moreover, this article analyzes the characteristics, properties, advantages, and disadvantages of various animal models of anxiety disorders and PTSD. It offers an overview of the pathophysiology, treatments, prevalence, and symptoms of anxiety disorders in the clinics. Furthermore, it comprehensively discusses pharmacological treatments and neural mechanisms, as well as the types and properties of the animal models of anxiety disorders in shaping and testing anxiety behaviors. In light of the previous literature discussion, we can understand the different functions of the animal models of anxiety disorders and PTSD to help us link preclinical and clinical research. Animal models are used in advanced drug discovery programs, specifically in psychiatry and neuroscience research. The challenge for the future will be to keep pace with developing the appropriate animal models of anxiolytic drugs to improve the translation of large datasets obtained to clinics.

GABAergic implications in anxiety and related disorders

Evidence indicates that anxiety disorders arise from an imbalance in the functioning of brain circuits that govern the modulation of emotional responses to possibly threatening stimuli. The circuits under consideration in this context include the amygdala's bottom-up activity, which signifies the existence of stimuli that may be seen as dangerous. Moreover, these circuits encompass top-down regulatory processes that originate in the prefrontal cortex, facilitating the communication of the emotional significance associated with the inputs. Diverse databases (e.g., Pubmed, ScienceDirect, Web of Science, Google Scholar) were searched for literature using a combination of different terms e.g., "anxiety", "stress", "neuroanatomy", and "neural circuits", etc. A decrease in GABAergic activity is present in both anxiety disorders and severe depression. Research on cerebral functional imaging in depressive individuals has shown reduced levels of GABA within the cortical regions. Additionally, animal studies demonstrated that a reduction in the expression of GABAA/B receptors results in a behavioral pattern resembling anxiety. The amygdala consists of inhibitory networks composed of GABAergic interneurons, responsible for modulating anxiety responses in both normal and pathological conditions. The GABAA receptor has allosteric sites (e.g., α/γ, γ/β, and α/β) which enable regulation of neuronal inhibition in the amygdala. These sites serve as molecular targets for anxiolytic medications such as benzodiazepine and barbiturates. Alterations in the levels of naturally occurring regulators of these allosteric sites, along with alterations to the composition of the GABAA receptor subunits, could potentially act as mechanisms via which the extent of neuronal inhibition is diminished in pathological anxiety disorders.

The effect of SSRIs on fear learning: a systematic review and meta-analysis

RATIONALE

Selective serotonin reuptake inhibitors (SSRIs) are considered first-line medication for anxiety-like disorders such as panic disorder, generalized anxiety disorder, and post-traumatic stress disorder. Fear learning plays an important role in the development and treatment of these disorders. Yet, the effect of SSRIs on fear learning are not well known.

OBJECTIVE

We aimed to systematically review the effect of six clinically effective SSRIs on acquisition, expression, and extinction of cued and contextual conditioned fear.

METHODS

We searched the Medline and Embase databases, which yielded 128 articles that met the inclusion criteria and reported on 9 human and 275 animal experiments.

RESULTS

Meta-analysis showed that SSRIs significantly reduced contextual fear expression and facilitated extinction learning to cue. Bayesian-regularized meta-regression further suggested that chronic treatment exerts a stronger anxiolytic effect on cued fear expression than acute treatment. Type of SSRI, species, disease-induction model, and type of anxiety test used did not seem to moderate the effect of SSRIs. The number of studies was relatively small, the level of heterogeneity was high, and publication bias has likely occurred which may have resulted in an overestimation of the overall effect sizes.

CONCLUSIONS

This review suggests that the efficacy of SSRIs may be related to their effects on contextual fear expression and extinction to cue, rather than fear acquisition. However, these effects of SSRIs may be due to a more general inhibition of fear-related emotions. Therefore, additional meta-analyses on the effects of SSRIs on unconditioned fear responses may provide further insight into the actions of SSRIs.

Trigeminal neuropathic pain reduces 50-kHz ultrasonic vocalizations in rats, which are restored by analgesic drugs

Trigeminal neuralgia (TN) is a severe form of neuropathic pain frequently associated with anxiety. The chronic constriction injury of the infraorbital nerve (CCI-ION) of rodents is a well-established model to study sensory alterations related to TN. However, few studies have addressed the emotional component of pain, which is fundamental to increase its translational capability. Emission of ultrasonic vocalization (USV) is considered a reliable measure of the emotional state of rats. Rats emit 50-kHz USVs in social and appetitive situations, whereas 22-kHz USVs may index a negative state. Studies suggest that persistent pain causes reduction in 50-kHz calls, but this may also indicate anxiety-like behavior. Thus, we hypothesize that CCI-ION would decrease 50-kHz calls and that pharmacological pain relief would restore USVs, without interfering with anxiety-like behavior. On day 15 after surgery, male rats were treated with local lidocaine, midazolam or carbamazepine to determine their effect on facial mechanical hyperalgesia, USV and anxiety-like behavior. The results showed that CCI-ION induced hyperalgesia, which was attenuated by lidocaine or carbamazepine, developed anxiety-like behavior, which was reduced only by midazolam, and displayed a reduced number of 50-kHz calls, compared to sham. Lidocaine and carbamazepine increased 50-kHz calls emitted by CCI-ION rats, but midazolam failed to change them. These data add information on the translational aspects of CCI-ION model and carbamazepine treatment for trigeminal neuropathic pain. Furthermore, they suggest that the reduction of USV in persistent pain conditions is related to spontaneous pain and reinforce the idea that it reflects the emotional component of pain.

The effectiveness of lamotrigine for persistent depressive disorder: A case report

Aim

Persistent depressive disorder (PDD) was first introduced in the Diagnostic and Statistical Manual of Mental Disorders 5th edition (DSM‐5), which encompasses numerous different conditions, including dysthymia, recurrent major depressive disorder, double depression, and chronic major depression. SSRIs are the first‐line drugs for treatment of PDD; however, not all patients respond to SSRI treatment.

Case presentation

We describe a woman who was diagnosed with PDD. At the age of 38, the patient presented with anxiety, reduced energy, marked tiredness, and sleep disturbances. She was prescribed with three antidepressants (paroxetine, duloxetine, and mirtazapine), which were not effective in relieving her symptoms. She was also prescribed bromazepam, which was also not effective. Subsequently, she was switched to lamotrigine, which resulted in a marked improvement in symptoms. The antidepressants and bromazepam were gradually tapered and discontinued.

Conclusion

This case demonstrates that lamotrigine may be effective for treating patients with antidepressant resistant PDD and suggests that it may be a promising alternative to combination therapy of antidepressants and benzodiazepines in the treatment of PDD.

The patient's depressive and anxiety symptoms remitted and relapsed repeatedly during taking combination therapy. After switching to lamotrigine monotherapy, the symptoms have improved and continued remission for a long time.

Pharmacotherapy of Anxiety Disorders: Current and Emerging Treatment Options

(Appeared originally in Frontiers in Psychiatry 2020 Dec 23; 11:595584)

Pharmacotherapy of Anxiety Disorders: Current and Emerging Treatment Options

Anxiety disorders are the most prevalent psychiatric disorders and a leading cause of disability. While there continues to be expansive research in posttraumatic stress disorder (PTSD), depression and schizophrenia, there is a relative dearth of novel medications under investigation for anxiety disorders. This review's first aim is to summarize current pharmacological treatments (both approved and off-label) for panic disorder (PD), generalized anxiety disorder (GAD), social anxiety disorder (SAD), and specific phobias (SP), including selective serotonin reuptake inhibitors (SSRIs), serotonin norepinephrine reuptake inhibitors (SNRIs), azapirones (e.g., buspirone), mixed antidepressants (e.g., mirtazapine), antipsychotics, antihistamines (e.g., hydroxyzine), alpha- and beta-adrenergic medications (e.g., propranolol, clonidine), and GABAergic medications (benzodiazepines, pregabalin, and gabapentin). Posttraumatic stress disorder and obsessive-compulsive disorder are excluded from this review. Second, we will review novel pharmacotherapeutic agents under investigation for the treatment of anxiety disorders in adults. The pathways and neurotransmitters reviewed include serotonergic agents, glutamate modulators, GABAergic medications, neuropeptides, neurosteroids, alpha- and beta-adrenergic agents, cannabinoids, and natural remedies. The outcome of the review reveals a lack of randomized double-blind placebo- controlled trials for anxiety disorders and few studies comparing novel treatments to existing anxiolytic agents. Although there are some recent randomized controlled trials for novel agents including neuropeptides, glutamatergic agents (such as ketamine and d-cycloserine), and cannabinoids (including cannabidiol) primarily in GAD or SAD, these trials have largely been negative, with only some promise for kava and PH94B (an inhaled neurosteroid). Overall, the progression of current and future psychopharmacology research in anxiety disorders suggests that there needs to be further expansion in research of these novel pathways and larger-scale studies of promising agents with positive results from smaller trials.

Glutamate Systems in DSM-5 Anxiety Disorders: Their Role and a Review of Glutamate and GABA Psychopharmacology

Serotonin reuptake inhibitors and benzodiazepines are evidence-based pharmacological treatments for Anxiety Disorders targeting serotonin and GABAergic systems, respectively. Although clearly effective, these medications fail to improve anxiety symptoms in a significant proportion of patients. New insights into the glutamate system have directed attention toward drugs that modulate glutamate as potential alternative treatments for anxiety disorders. Here we summarize the current understanding of the potential role of glutamate neurotransmission in anxiety disorders and highlight specific glutamate receptors that are potential targets for novel anxiety disorder treatments. We also review clinical trials of medications targeting the glutamate system in DSM-5 anxiety disorders. Understanding the role of the glutamate system in the pathophysiology of anxiety disorder may aid in developing novel pharmacological agents that are effective in treating anxiety disorders.

N-propyl-2,2-diphenyl-2-hydroxyacetamide, a novel α-hydroxyamide with anticonvulsant, anxiolytic and antidepressant-like effects that inhibits voltage-gated sodium channels

In patients with epilepsy, anxiety and depression are the most frequent psychiatric comorbidities but they often remain unrecognized and untreated. We report herein the antidepressant-like activity in two animal models, tail suspension and forced swimming tests, of six anticonvulsants α-hydroxyamides. From these, N-propyl-2,2-diphenyl-2-hydroxyacetamide (compound 5) emerged not only as the most active as anticonvulsant (ED₅₀ = 2.5mg/kg, MES test), but it showed the most remarkable antidepressant-like effect in the tail suspension and forced swimming tests (0.3-30mg/kg, i.p.); and, also, anxiolytic-like action in the plus maze test (3-10mg/kg, i.p.) in mice. Studies of its mechanism of action, by means of its capacity to act via the GABA_A receptor ([³H]-flunitrazepam binding assay); the 5-HT_1A receptor ([³H]-8-OH-DPAT binding assay) and the voltage-gated sodium channels (either using the patch clamp technique in hNa_v 1.2 expressed in HEK293 cell line or using veratrine, in vivo) were attempted. The results demonstrated that its effects are not likely related to 5-HT_1A or GABA_Aergic receptors and that its anticonvulsant and antidepressant-like effect could be due to its voltage-gated sodium channel blocking properties.

Lamotrigine, an antiepileptic drug, inhibits 5-HT3 receptor currents in NCB-20 neuroblastoma cells

Lamotrigine is an antiepileptic drug widely used to treat epileptic seizures. Using whole-cell voltage clamp recordings in combination with a fast drug application approach, we investigated the effects of lamotrigine on 5-hydroxytryptamine (5-HT)₃ receptors in NCB-20 neuroblastoma cells. Co-application of lamotrigine (1~300 µM) resulted in a concentration-dependent reduction in peak amplitude of currents induced by 3 µM of 5-HT for an IC₅₀ value of 28.2±3.6 µM with a Hill coefficient of 1.2±0.1. These peak amplitude decreases were accompanied by the rise slope reduction. In addition, 5-HT₃-mediated currents evoked by 1 mM dopamine, a partial 5-HT₃ receptor agonist, were inhibited by lamotrigine co-application. The EC₅₀ of 5-HT for 5-HT₃ receptor currents were shifted to the right by co-application of lamotrigine without a significant change of maximal effect. Currents activated by 5-HT and lamotrigine co-application in the presence of 1 min pretreatment of lamotrigine were similar to those activated by 5-HT and lamotrigine co-application alone. Moreover, subsequent application of lamotrigine in the presence of 5-HT and 5-hydroxyindole, known to attenuate 5-HT₃ receptor desensitization, inhibited 5-HT₃ receptor currents in a concentration-dependent manner. The deactivation of 5-HT₃ receptor was delayed by washing with an external solution containing lamotrigine. Lamotrigine accelerated the desensitization process of 5-HT₃ receptors. There was no voltage-dependency in the inhibitory effects of lamotrigine on the 5-HT₃ receptor currents. These results indicate that lamotrigine inhibits 5-HT₃-activated currents in a competitive manner by binding to the open state of the channels and blocking channel activation or accelerating receptor desensitization.

Effects of standardized Ginkgo biloba extract on the acquisition, retrieval and extinction of conditioned suppression: Evidence that short-term memory and long-term memory are differentially modulated

Studies in our laboratory have characterized the putative neuromodulatory effects of a standardized extract of the green leaves of Ginkgo biloba (EGb), which comprises a formulation of 24% ginkgo-flavoglycosides and 6% ginkgo-terpenoid lactones, on conditioned suppression. This model comprises a suitable animal model for investigating the behavioral changes and pharmacological mechanisms that underlie fear memory and anxiety. The characterization of the effects on distinct stages of fear memory or fear extinction will help illustrate both the beneficial and harmful effects. Three hundred adult male Wistar rats were randomly assigned to 30 groups according to the treatment as follows: i-ii) control groups (CS-US and CSno-US); iii) vehicle group (12% Tween®80); and iv-vi) EGb groups (250, 500 and 1000mgkg(-1)); or experimental procedures designed to assess the effects of EGb treatment prior to the acquisition (n=20 per group) and retrieval of conditioned fear (n=10 per group) or prior to the extinction training (n=10 per group) and extinction retention test (n=10 per group). Furthermore, to better understand the effects of acute EGb treatment on fear memory, we conducted two additional analyses: the acquisition of within- and between-session extinction of fear memory (short- and long-term memory, respectively). No difference was identified between the control and treatment groups during the retention test (P>0.05), with the exception of the CSno-US group in relation to all groups (P<0.05). A between-session analysis indicated that EGb at 250mgkg(-1) facilitated the acquisition of extinction fear memory, which was verified by the suppression ration in the first trial of extinction training (SR=0.39) and the extinction retention test session (SR=0.53, P<0.05), without impairments in fear memory acquisition, which were evaluated during the retention test (SR=0.79). Moreover, EGb administered at 1000mgkg(-1) prior to conditioning did not enhance the long-term extinction memory, i.e., it did not prevent the return of extinguished fear memory in the extinction retention test, in which the spontaneous recovery of fear was demonstrated (SR=0.63, P<0.05); however, it significantly facilitated short-term memory as verified by data from the within-session extinction (1 to 8-10 trials) during the retention test (SR=0.73 to SR=0.59; P<0.05) and the extinction retention test (SR=0.63 to SR=0.41; P<0.05). Moreover, spontaneous recovery was identified in response to a higher dose of EGb when administered prior to extinction training (SR=0.75, P<0.05) and the extinction retention test (SR=0.70; P<0.05). At dose of 500mgkg(-1) EGb reduced the suppression ratio when administered prior to the retention test (SR=0.57) and extinction training (SR=0.55; P<0.05) without preventing the acquisition of fear memory, which suggests that EGb has anti-anxiety effects. Taken together, the current findings suggest that EGb differentially modulates short- and long-term memory, as well as anxiety-like behavior. The actions of EGb may provide information regarding the beneficial effects in the prevention and treatment of neurocognitive impairments and anxiety disorders. Additional analyses are necessary to facilitate an understanding of these effects; however, previous data from our group suggest that GABAergic, serotoninergic and glutamatergic receptors are potential targets of the effects of EGb on conditioned suppression.

Effects of a Flavonoid-Rich Fraction on the Acquisition and Extinction of Fear Memory: Pharmacological and Molecular Approaches

The effects of flavonoids have been correlated with their ability to modulate the glutamatergic, serotoninergic, and GABAergic neurotransmission; the major targets of these substances are N-methyl-D-aspartic acid receptor (NMDARs), serotonin type1A receptor (5-HT_1ARs), and the gamma-aminobutyric acid type A receptors (GABA_ARs). Several studies showed that these receptors are involved in the acquisition and extinction of fear memory. This study assessed the effects of treatment prior to conditioning with a flavonoid-rich fraction from the stem bark of Erythrina falcata (FfB) on the acquisition and extinction of the conditioned suppression following pharmacological manipulations and on gene expression in the dorsal hippocampus (DH). Adult male Wistar rats were treated before conditioned fear with FfB, vehicle, an agonist or antagonist of the 5-HT_1AR, GABA_ARs or the GluN2B-NMDAR or one of these antagonists before FfB treatment. The effects of these treatments on fear memory retrieval, extinction training and extinction retrieval were evaluated at 48, 72, and 98 h after conditioning, respectively. We found that activation of GABA_ARs and inactivation of GluN2B-NMDARs play important roles in the acquisition of lick response suppression. FfB reversed the effect of blocking GluN2B-NMDARs on the conditioned fear and induced the spontaneous recovery. Blocking the 5-HT_1AR and the GluN2B-NMDAR before FfB treatment seemed to be associated with weakening of the spontaneous recovery. Expression of analysis of DH samples via qPCR showed that FfB treatment resulted in the overexpression of Htr1a, Grin2a, Gabra5, and Erk2 after the retention test and of Htr1a and Erk2 after the extinction retention test. Moreover, blocking the 5-HT1ARs and the GluN2B-NMDARs before FfB treatment resulted in reduced Htr1a and Grin2b expression after the retention test, but played a distinct role in Grin2a and Erk2 expression, according session evaluated. We show for the first time that the serotoninergic and glutamatergic receptors are important targets for the effect of FfB on the conditioned fear and spontaneous recovery, in which the ERK signaling pathway appears to be modulated. Further, these results provide important information regarding the role of the DH in conditioned suppression. Taken together, our data suggest that FfB represents a potential therapy for preventing or treating memory impairments.

Inhibition of voltage-gated Na+ channels by hinokiol in neuronal cells

BACKGROUND

Hinokiol is a naturally occurring diterpenoid compound isolated from plants such as Taiwania cryptomerioides. Anti-oxidation, anti-cancer, and anti-inflammation effects of this compound have been reported. It is not yet known if hinokiol affects neurons or neuronal ion channel activities. We reported here that hinokiol inhibited voltage-gated Na(+) channels (VGSC) in neuronal cells and we characterized the mechanisms of block.

METHODS

The effects of hinokiol on Na(+) channels were examined using the voltage-clamp (whole-cell mode) technique.

RESULTS

VGSC was blocked by hinokiol in a concentration-dependent and state-dependent manner in neuroblastoma N2A cells: IC(50) are 11.3 and 37.4μM in holding potentials of -70 and -100 mV, respectively. In the presence of hinokiol there was a 13-mV left shift in steady-state inactivation curves; however, activation gating was not altered. VGSC inhibition by hinokiol did not require channel opening and was thus considered to be closed-channel block. In the presence of hinokiol, since the degree of block did not enhance with stimulation frequency, block by hinokiol thus did not exhibit use-dependence. Recovery from channel inactivation was not significantly affected in the presence of hinokiol. In addition, hinokiol also inhibited VGSC of differentiated neuronal NG108-15 cells and rat hippocampal CA1 neurons.

CONCLUSION

Our results therefore suggest hinokiol inhibited VGSC in a closed-channel block manner and such inhibition involved intensification of channel inactivation.

Scn8a voltage-gated sodium channel mutation alters seizure and anxiety responses to acute stress

Stress is known to trigger seizures in patients with epilepsy, highlighting the physiological stress response as a possible therapeutic target for epilepsy treatment. Nevertheless, little is currently known about how a genetic predisposition to epilepsy interacts with the stress response to influence seizure outcome. To address this question, we examined the effect of acute stress on seizure outcome in mice with mutations in the voltage-gated sodium channel (VGSC) gene Scn8a. Scn8a mutants display spontaneous spike-wave discharges (SWDs) characteristic of absence epilepsy. We saw that the baseline frequency of SWDs in Scn8a mutants correlates closely with the diurnal activity of the hypothalamic-pituitary-adrenal (HPA) axis, with a peak in seizure activity occurring at around the same time as the peak in corticosterone (1700-1900h). A 20-min acute restraint stress administered in the morning increases the frequency of spontaneous SWDs immediately following the stressor. Seizure frequency then returns to baseline levels within 3h after stressor exposure, but the subsequent evening peak in seizure frequency is delayed and broadened, changes that persist into the next evening and are accompanied by long-lasting changes in HPA axis activity. Scn8a mutants also show increased anxiety-like behavior in mildly stressful situations. A 20-min acute restraint stress can also increase the severity and duration of chemically induced seizures in Scn8a mutants, changes that differ from wild-type littermates. Overall, our data show that a voltage-gated sodium channel mutation can alter the behavioral response to stress and can interact with the stress response to alter seizure outcome.

Suppression of voltage-gated Na(+) channels and neuronal excitability by imperatorin

Imperatorin is a naturally occurring furocoumarin compound isolated from plants such as Angelica archangelica and Cnidium monnieri. It has multiple pharmacological effects including anticonvulsant effects. Here we determined the effects of imperatorin on voltage-gated Na(+) channels (VGSC) using whole-cell patch clamp techniques in differentiated neuronal NG108-15 cells. We showed that imperatorin inhibited VGSC; such inhibition did not show state-dependence. Imperatorin caused a left shift in the steady-state inactivation curve without affecting activation gating. The inhibition of VGSC by imperatorin displayed a mild frequency-dependence. Imperatorin was also shown to inhibit VGSC and action potential amplitude without affecting voltage-gated K(+) channels in rat hippocampal CA1 neurons. In conclusion, our results suggest that imperatorin dampens neuronal excitability by inhibiting VGSC.

Lamotrigine increases intracellular Ca(2+) levels and Ca(2+)/calmodulin-dependent kinase II activation in mouse dorsal root ganglion neurones

AIM

Lamotrigine is a neuroprotective agent that is used clinically for the treatment of seizures and neuropathic pain. A significant volume of literature has reported that lamotrigine exerts analgesic effect by blocking Ca(2+) channels. However, little is known regarding the effect of lamotrigine on the intracellular Ca(2+) concentration ([Ca(2+)](i)). The aim of this study was to determine whether lamotrigine modulates [Ca(2+)](i) in sensory neurones.

METHODS

Lamotrigine-induced changes in [Ca(2+)](i) were measured in mouse dorsal root ganglion (DRG) neurones using the Ca(2+)-sensitive fluorescent indicator Fluo 3-AM and a confocal laser scanning microscope. Ca(2+)/calmodulin-dependent kinase II (CaMKII) activation was assessed by the fluorescence intensity using immunocytochemical procedures.

RESULTS

Treatment with 1, 10, 30 or 100 μM lamotrigine transiently increased [Ca(2+)](i) in DRG neurones in a dose-dependent manner. Treatment with 100 μM lamotrigine induced a significant (threefold) increase in the Ca(2+) peak in the presence or absence of extracellular Ca(2+). The lamotrigine-induced Ca(2+) increase was abolished or decreased by the treatment with a specific PLC inhibitor (U73122), IP3R antagonist (xestospongin C) or RyR antagonist (dantrolene). In some cells, treatment with 100 μM lamotrigine caused a transient Ca(2+) increase, and the Ca(2+) levels quickly fell to below the basal Ca(2+) level observed prior to lamotrigine application. The decrease in basal Ca(2+) levels was blocked by the treatment with a CaMKII inhibitor (KN93). Immunocytochemical analysis indicated that lamotrigine treatment increased the expression of phosphorylated CaMKII in DRG neurones.

CONCLUSION

Treatment with lamotrigine increased [Ca(2+)](i) apparently as a result of Ca(2+) release from intracellular stores and CaMKII activity.

Botany, traditional uses, phytochemistry and pharmacology of Apocynum venetum L. (Luobuma): A review

ETHNOPHARMACOLOGICAL RELEVANCE

Apocynum venetum L. (Apocynaceae, Luobuma ) has a long history as a Chinese traditional medicine with uses to calm the liver, soothe the nerves, dissipate heat, and promote diuresis. Recently, Luobuma tea has been commercialized as a sedative and anti-aging supplement that has become increasingly popular in North American and East Asian health food markets.

AIMS OF THE REVIEW

The aim of this review is to provide an up-to-date and comprehensive overview of the botany, chemical constituents, traditional uses, pharmacological activities and safety aspects of Apocynum venetum in order to assess its ethnopharmacological use and to explore its therapeutic potentials and future opportunities for research.

BACKGROUND AND METHODS

The accessible literature on Apocynum venetum written in English, Chinese and Japanese were collected and analyzed. The literatures included ancient Chinese herbal classics, pharmacopoeias and articles that included in Pubmed, Web of Science, Google Scholar and Wanfang.

KEY FINDINGS

Modern pharmacological studies demonstrated that Apocynum venetum possess wide pharmacological activities that include antihypertensive, cardiotonic, hepatoprotective, antioxidant, lipid-lowering, antidepressant and anxiolytic effects, which can be explained by the presence of various flavonoid compounds in this plant. The traditional (Lop Nor region) use of Apocynum venetum with tobacco as an agent to detoxify nicotine may receive interest as a possible therapeutic option to detoxify the body from smoking. Based on animal studies and clinical trials, Apocynum venetum causes no severe side effects, even in a stable daily dosage (50mg/person/day) for more than three years.

CONCLUSIONS

Apocynum venetum potentially has therapeutic potential in the prevention and treatment for the cardiovascular and neurological diseases, especially for high blood pressure, high cholesterol, neurasthenia, depression and anxiety. Further investigations are needed to explore individual bioactive compounds responsible for these in vitro and in vivo pharmacological effects and the mode of actions. Further safety assessments and clinical trials should be performed before it can be integrated into medicinal practices.

Effect of lamotrigine and carbamazepine on corticotropin-releasing factor-associated serotonergic transmission in rat dorsal raphe nucleus

Corticotropin-releasing factor (CRF) and serotonin are important transmitters of the pathophysiology of mood disorder. To clarify the mechanisms of action of lamotrigine (LTG) and carbamazepine (CBZ), we determined their effects on serotonin release associated with CRF in rat dorsal raphe nucleus (DRN) and median prefrontal cortex (mPFC) using dual-probe microdialysis. Neither perfusion with CRF1 nor CRF2 antagonists into DRN-affected serotonin release in DRN and mPFC. Perfusion of 10 μM CRF into DRN increased serotonin release in both regions, whereas 0.1 μM CRF decreased and had no effect on serotonin release in DRN and mPFC, respectively. Pre-perfusion with CRF1 antagonist into DRN inhibited 0.1 μM CRF-induced serotonin reduction, whereas pre-perfusion with CRF2 antagonist in DRN inhibited 10 μM CRF-induced serotonin elevation, without affecting 0.1 μM CRF-induced serotonin reduction. LTG perfusion concentration dependently decreased serotonin releases in DRN and mPFC. Therapeutic and supratherapeutic concentrations of CBZ increased and decreased serotonin releases in both regions, respectively. Pre-perfusion with sub-therapeutic concentration LTG inhibited CRF1-induced serotonin reduction without affecting CRF2-induced serotonin release, whereas pre-perfusion with therapeutic concentration of LTG inhibited both CRF1- and CRF2-actions. In contrast, both therapeutic and supratherapeutic concentrations of CBZ inhibited CRF2-induced serotonin release without affecting CRF1-induced serotonin reduction. Neither LTG nor CBZ affected the CRF-induced cAMP production in cells over-expressing CRF1 and CRF2 receptors. This study demonstrated that inhibition of CRF2-receptor-mediated serotonergic transmission is a mechanism shared by LTG and CBZ, two clinically related compounds, whereas LTG but not CBZ inhibits CRF1-receptor-mediated serotonergic transmission. Therefore, these mechanisms may contribute to the clinical actions of these agents.

Inhibitory effects of magnolol on voltage-gated Na+ and K+ channels of NG108-15 cells

Magnolol, a polyphenolic compound isolated from Houpu, a Chinese herb from the bark of Magnolia officinalis, has been reported to have in vitro and in vivo neuroprotective effects. In spite of these reported beneficial effects, studies on the direct impact of magnolol on neuronal ion channels have been scarce. Whether magnolol affects voltage-gated Na(+) channels (VGSC) and voltage-gated K(+) (Kv) channels is unknown. Using the whole-cell voltage-clamp method, we studied the effects of magnolol on voltage-gated ion channels in neuronal NG108-15 cells. Magnolol inhibited VGSC channels with mild state-dependence (IC(50) of 15 and 30 μM, at holding potentials of -70 and -100 mV, respectively). No frequency-dependence was observed in magnolol block. Magnolol caused a left-shift of 18 mV in the steady-state inactivation curve but did not affect the voltage-dependence of activation. Magnolol inhibited Kv channels with an IC(50) of 21 μM, and it caused a 20-mV left-shift in the steady-state inactivation curve without affecting the voltage-dependence of activation. In conclusion, magnolol is an inhibitor of both VGSC and Kv channels and these inhibitory effects may in part contribute to some of the reported neuroprotective effects of magnolol.

Riluzole produces distinct anxiolytic-like effects in rats without the adverse effects associated with benzodiazepines

In this study, we investigated the anxiolytic-like effect of riluzole using three different innate anxiety models in rats. In the elevated plus-maze test, riluzole significantly increased the time spent in, and entries into, the open arm after 60 min administration. This finding was supported by results obtained from light/dark and open-field tests. The magnitude of the anxiolytic-like effects of riluzole in each of the behavioral models was similar to those produced by a benzodiazepine, diazepam, suggesting that riluzole has a robust anxiolytic-like activity in rats. To clarify the involvement of sodium channels in this anxiolytic activity, we examined the effect of a co-administered sodium channel activator, veratrine. The anxiolytic-like action of riluzole was diminished by veratrine in the elevated plus-maze, light/dark and open-field tests. Based on these results, it is suggested that the anxiolytic mechanism of riluzole is clearly distinct from that of diazepam. In addition, to examine whether riluzole directly and non-selectively affected the GABA(A)-benzodiazepine receptor complex, we performed three behavioral tests (footprint analysis, Y-maze test and the ethanol-induced sleeping time test) that are closely related to the GABA(A)-benzodiazepine pathways. In contrast to diazepam, riluzole produced no significant effects in these tests. Here, we provide the first report demonstrating that riluzole produces distinct anxiolytic-like effects in rats without the adverse effects associated with benzodiazepines.

Antidepressant-like properties of oral riluzole and utility of incentive disengagement models of depression in mice

RATIONALE

The neuroprotective agent riluzole has antidepressant-like properties in humans, but its mechanisms of action are unclear. Despite the increasing utility of transgenic and knockout mice in addressing such issues, previous studies aimed at characterizing biochemical mechanisms have been conducted in rats.

OBJECTIVES

We sought to optimize an oral riluzole administration protocol with antidepressant-like consequences in C57BL/6 mice, a common background strain in genetically modified mice.

METHODS

Riluzole (6-60 μg/ml) was dissolved in tap water and replaced regular drinking water for up to 3 weeks; sensitivity to tail suspension, forced swimming, and the locomotor response to extinction training in a model of "incentive disengagement" were tested. Peripheral and central effects of long-term 60-μg/ml treatment were also evaluated.

RESULTS

Riluzole had dose-dependent antidepressant-like effects in the forced swim test, and like chronic fluoxetine, exerted antidepressant-like actions in an adaptation of the "incentive disengagement" model at the highest concentration tested. This 60-μg/ml concentration also restored hippocampal brain-derived neuroptrophic factor (BDNF) expression after chronic corticosteroid exposure and increased glutamate glial transporter 1 (GLT-1, or EAAT2) expression without significantly affecting baseline locomotor activity, thymus and adrenal gland weights, or blood serum corticosterone. The lowest 6-μg/ml concentration increased locomotor activity, potentially consistent with an anxiolytic-like effect.

CONCLUSIONS

Riluzole's therapeutic potential for treating mood disorders may involve GLT-1 and BDNF, and we suggest this protocol could be used to further characterize its precise long-term biochemical mechanisms of action in animal models of depression.

Apocynum venetum leaf aqueous extract inhibits voltage-gated sodium channels of mouse neuroblastoma N2A cells

ETHNOPHARMACOLOGICAL RELEVANCE

Apocynum venetum Linn. (Apocynaceae family), also called Luobuma, is a shrub which grows widely in the Xinjiang Autonomous Region of China. Its leaves are used in herbal tea for the treatment of hypertension, anxiety and depression. Animal studies have also shown that Apocynum venetum leaf extract (AVLE) also exerts anti-depressant and anti-anxiety activities. The effects of AVLE on neuronal tissues in vitro are not fully understood.

MATERIALS AND METHODS

Using the whole-cell voltage-clamp method, we studied the effects of AVLE on ion channels in cultured mouse neuroblastoma N2A cells.

RESULTS

AVLE inhibited voltage-gated inward Na(+) current in a reversible and concentration-dependent manner (half-inhibitory concentration was 18 μg/ml and maximum inhibition at 100 μg/ml). AVLE specifically promoted steady-state inactivation of Na(+) channels but did not affect voltage-dependence of activation. The inhibitory effect was not use-dependent and was not affected by 300μM L-NAME, suggesting that NO was not involved in the action of AVLE in neuronal cells. AVLE also had a mild inhibitory effect on voltage-gated K(+) channels, but did not affect ATP-sensitive K(+) channels.

CONCLUSIONS

Since voltage-gated Na(+) and K(+) channels are associated with neuronal excitability and therefore affect neurotransmission, the modulation of neuronal ion channels by AVLE may exert neuropharmacological effects. In particular, the inhibition of voltage-gated Na(+) currents by AVLE may in part account for the psychopharmacological effects of this herbal remedy.

New perspectives in glutamate and anxiety

Anxiety and stress-related disorders, namely posttraumatic stress disorder (PTSD), generalized anxiety disorder (GAD), obsessive-compulsive disorder (ODC), social and specific phobias, and panic disorder, are a major public health issue. A growing body of evidence suggests that glutamatergic neurotransmission may be involved in the biological mechanisms underlying stress response and anxiety-related disorders. The glutamatergic system mediates the acquisition and extinction of fear-conditioning. Thus, new drugs targeting glutamatergic neurotransmission may be promising candidates for new pharmacological treatments. In particular, N-methyl-d-aspartate receptors (NMDAR) antagonists (AP5, AP7, CGP37849, CGP39551, LY235959, NPC17742, and MK-801), NMDAR partial agonists (DCS, ACPC), α-amino-3-hydroxyl-5-methyl-4-isoxazole-propionate receptors (AMPARs) antagonists (topiramate), and several allosteric modulators targeting metabotropic glutamate receptors (mGluRs) mGluR1, mGluR2/3, and mGluR5, have shown anxiolytic-like effects in several animal and human studies. Several studies have suggested that polyamines (agmatine, putrescine, spermidine, and spermine) may be involved in the neurobiological mechanisms underlying stress-response and anxiety-related disorders. This could mainly be attributed to their ability to modulate ionotropic glutamate receptors, especially NR2B subunits. The aim of this review is to establish that glutamate neurotransmission and polyaminergic system play a fundamental role in the onset of anxiety-related disorders. This may open the way for new drugs that may help to treat these conditions.

Pharmacodynamics of memantine: an update

Memantine received marketing authorization from the European Agency for the Evaluation of Medicinal Products (EMEA) for the treatment of moderately severe to severe Alzheimer s disease (AD) in Europe on 17(th) May 2002 and shortly thereafter was also approved by the FDA for use in the same indication in the USA. Memantine is a moderate affinity, uncompetitive N-methyl-D-aspartate (NMDA) receptor antagonist with strong voltage-dependency and fast kinetics. Due to this mechanism of action (MOA), there is a wealth of other possible therapeutic indications for memantine and numerous preclinical data in animal models support this assumption. This review is intended to provide an update on preclinical studies on the pharmacodynamics of memantine, with an additional focus on animal models of diseases aside from the approved indication. For most studies prior to 1999, the reader is referred to a previous review [196].In general, since 1999, considerable additional preclinical evidence has accumulated supporting the use of memantine in AD (both symptomatic and neuroprotective). In addition, there has been further confirmation of the MOA of memantine as an uncompetitive NMDA receptor antagonist and essentially no data contradicting our understanding of the benign side effect profile of memantine.

The anti-epileptic drug lacosamide (Vimpat) has anxiolytic property in rodents

Lacosamide ((R)-2-acetamido-N-benzyl-3-methoxypropionamide; formerly harkoseride, SPM 927; Vimpat), has been recently approved by US and European regulatory authorities for use as add-on therapy for partial-onset seizures in adults. Because a number of anti-epileptic drugs are used to treat conditions beyond epilepsy, including anxiety, in the present study we investigated the anxiolytic potential of lacosamide in a conditioned emotional response (CER) model in rat, and the mouse marble burying assay. In each test lacosamide produced a significant effect consistent with anxiolysis, i.e. lacosamide increased suppression ratio in the CER test, and reduced the number of marbles buried in the marble burying assay. The doses necessary for an anxiolytic effect were higher than those necessary for efficacy in seizure tests conducted in the same species. For example in the mouse, the lacosamide oral ED(50) in the maximal electroshock seizure (MES) and 6 Hz tests was 5.3 and 9.6 mg/kg respectively, and the minimal effective dose in the marble burying assay was 30 mg/kg. In both seizure and anxiety tests, the (S)-enantiomer of lacosamide was inactive suggesting a similar mechanism of action, possibly use-dependent inhibition of sodium channel function (Errington et al., 2008). Efficacy in the CER model was equivalent to diazepam and pregabalin (Lyrica). In tests of side-effects, lacosamide had no effect on choice accuracy in the delayed match to position task of working memory, although at the 30 mg/kg dose, response rates and response latencies were significantly affected. In sum, the present results identify for the first time, an anxiolytic potential of lacosamide.

Differential effects of MPEP and diazepam in tests of conditioned emotional response and Pavlovian-to-instrumental transfer suggests 'anxiolytic' effects are mediated by different mechanisms

BACKGROUND

The selective mGluR5 antagonist 2-methyl-6-(phenylethynyl)-pyridine (MPEP) is reported to be anxiolytic in several animal models of anxiety, including the conditioned emotional response (CER) paradigm. Suppression of responding during conditioned stimulus (CS) presentation in CER may reflect behavioural competition between lever pressing and adopting a shock-avoidance posture, or it may alternatively reflect altered value of the food reward following its association with a footshock, thus reducing its ability to motivate responding. If this is the case, then drugs that reduce the CER may interfere with the mechanism by which CSs are able to motivate responding, rather than by reducing anxiety. The standard test of the ability of Pavlovian cues to motivate responding is the Pavlovian-to-instrumental transfer (PIT) paradigm and it has recently been suggested that CER may be 'negative PIT'.

MATERIALS AND METHODS

We compared the effect of MPEP (0, 3, 10 and 30 mg/kg) and diazepam (0, 1, 3 and 10 mg/kg) in CER and PIT.

RESULTS

Both MPEP and diazepam significantly reduced conditioned suppression in the CER paradigm. MPEP, but not diazepam, significantly reduced PIT.

CONCLUSION

The findings support the hypothesis that MPEP may reduce expression of anxiety in the CER paradigm by interfering with the way in which emotionally salient cues are able to affect behaviour, but do not support such an analysis of the effect of diazepam. Diazepam and MPEP may therefore achieve their effects in CER by influencing different psychological processes.

Psychotherapeutic benefits of opioid agonist therapy

Opioids have been used for centuries to treat a variety of psychiatric conditions with much success. The so-called "opium cure" lost popularity in the early 1950s with the development of non-addictive tricyclic antidepressants and monoamine oxidase inhibitors. Nonetheless, recent literature supports the potent role of methadone, buprenorphine, tramadol, morphine, and other opioids as effective, durable, and rapid therapeutic agents for anxiety and depression. This article reviews the medical literature on the treatment of psychiatric disorders with opioids (notably, methadone and buprenorphine) in both the non-opioid-dependent population and in the opioid-dependent methadone maintenance population. The most recent neurotransmitter theories on the origin of depression and anxiety will be reviewed, including current information on the role of serotonin, N-Methyl d-Aspartate, glutamate, cortisol, catecholamine, and dopamine in psychiatric disorders. The observation that methadone maintenance patients with co-existing psychiatric morbidity (so called dual diagnosis patients) require substantially higher methadone dosages by between 20% and 50% will be explored and qualified. The role of methadone and other opioids as beneficial psychiatric medications that are independent of their drug abuse mitigating properties will be discussed. The mechanisms by which methadone and other opioids can favorably modulate the neurotransmitter systems controlling mood will also be discussed.

The role of the glutamatergic system in posttraumatic stress disorder

Antiglutamatergic agents, such as lamotrigine, have been used successfully for the treatment of posttraumatic stress disorder (PTSD). They could be potentially acting through the stabilization of the corticotropin-releasing factor (CRF) systems. Glutamate mediates CRF release in various brain regions involved in the pathophysiology of PTSD, antiglutamatergic agents could stabilize the CRF system and, thereby, improve the symptom complex of PTSD (reexperiencing, hyperarousal, and avoidance). The role of glutamate and CRF in PTSD and other anxiety disorders are still being elucidated. However, it is clear that the glutamatergic systems play a role in the pathophysiology of PTSD.

Antidepressant-like effect of lamotrigine is reversed by veratrine: a possible role of sodium channels in bipolar depression

Lamotrigine has been found to be efficacious in the acute management of bipolar depression and long-term management of bipolar disorder, especially in delaying depressive recurrence, either as monotherapy or as adjunctive therapy. Lamotrigine is also an antiepileptic drug, and is efficient in the treatment of focal epilepsies. It is thought to act by inhibition of glutamate release through blockade of voltage-sensitivity sodium channels and stabilization of the neuronal membrane.

OBJECTIVES

The scope of this study was to determinate if sodium channels are important for lamotrigine and other antidepressant to exert their antidepressant-like function.

METHODS

This study assessed the effects of veratrine, a Na(+) channel opener on antidepressant effect of lamotrigine and others antidepressants: two tricyclic antidepressants (TCAs): imipramine, a mixed serotonergic noradrenergic reuptake inhibitor, desipramine, a specific noradrenergic reuptake inhibitor and a SSRI: paroxetine, the most potent selective serotonergic reuptake inhibitor, using an animal model of depression, the forced swimming test. Veratrine (0.125 mg/kg) and lamotrigine (16, 32 mg/kg) or antidepressants (16, 32 mg/kg) were given i.p. 45 and 30 min, respectively, before the test.

RESULTS

We observed that when combined with veratrine the antidepressant-like effect of lamotrigine was reversed, but the antidepressant-like effect of the imipramine, desipramine and paroxetine was not changed, indicating that the mechanism of action of lamotrigine is different from that of antidepressants.

In vivo pharmacological effects of JZP-4, a novel anticonvulsant, in models for anticonvulsant, antimania and antidepressant activity

JZP-4 is a potent calcium and sodium channel blocker, which is currently being evaluated in patients as an anticonvulsant and mood stabilizer. In the current studies, JZP-4 was evaluated in a variety of animal models for anticonvulsant, antimania and antidepressant activity. In the mouse and rat maximal electroshock models, JZP-4 was slightly more potent than LTG. In the mouse pentylenetetrazole induced seizures model, JZP-4 was approximately twice as potent as lamotrigine in prolonging the time to clonus. In the mouse 6-Hz model for drug resistant or refractory epilepsy, JZP-4 had potent anticonvulsant activity at all current intensities, whereas LTG was active at only the lowest current intensity. In the mouse amphetamine-chlordiazepoxide model for antimanic effects, JZP-4, but not LTG, produced dose-related and significant effects at 3 and 10 mg/kg i.p. In the rat forced swim model of antidepressant activity, JZP-4 (30 mg/kg i.p.) produced a significant reduction in immobility and an increase in climbing behavior. LTG (30 mg/kg i.p.) produced similar effects but these effects did not achieve statistical significance. The specificity of this antidepressant response was confirmed in the rat locomotor test. In this test, JZP-4 produced dose-related and significant reductions in locomotor activity, indicating that it was not a CNS stimulant. LTG produced no significant effects in the rat locomotor test. The studies have demonstrated that JZP-4 has greater potency and efficacy than LTG in models of refractory epilepsy, antidepressant activity and antimania activity. The variance between the effects of LTG and JZP-4 may be related to the greater potency at sodium channels or the additional pharmacological actions of JZP-4 on calcium channels.

Veratrine blocks the lamotrigine-induced swimming increase and immobility decrease in the modified forced swimming test

Lamotrigine exhibits an anti-immobility effect in the modified forced swimming test, increasing swimming and climbing, behaviors that are related to serotonergic and noradrenergic effects, respectively. However, these effects could be secondary to lamotrigine blockade of Na(+) sensitive channel. Thus, this study investigated the influence of veratrine (0.1 mg/kg, ip, 10 min before each lamotrigine administration), an Na(+) channel activator, in the effect of lamotrigine (20 mg/kg, ip, 24, 5, 1 h before the test session) in the modified forced swimming test. Veratrine pre-treatment blocked lamotrigine-induced immobility decrease and swimming increase but it did not change the effect of lamotrigine on climbing. These results suggest that the serotonergic effect of lamotrigine in the modified forced swimming test is dependent on Na(+) voltage sensitive channel blockade, whereas its noradrenergic effect is not.

Antiepileptic drugs for the treatment of post-traumatic stress disorder

Post-traumatic stress disorder (PTSD) is a disruptive, chronic, and relatively common disorder that is often difficult to treat. Many patients with PTSD are unresponsive, have only moderate or marginal responses, or have troubling side effects to first-line serotonin reuptake inhibitor treatment. Studies suggest that antiepileptic drugs (AEDs) may be an effective treatment alternative or adjunctive treatment for the symptoms of PTSD. Recent results from case reports and open and controlled studies on the efficacy and tolerability of AEDs in PTSD are reviewed here, and their methodological limitations are discussed when relevant. AEDs shown to be effective in double-blind, placebo-controlled trials of PTSD include lamotrigine, topiramate, and tiagabine. Other AEDs that appear promising in open-label trials of PTSD include carbamazepine, valproate, gabapentin, vigabatrin, phenytoin, and levetiracetam. Stress-activated limbic kindling may be involved in the pathogenesis of PTSD. The possibility that AEDs may be effective in the treatment of PTSD due to their antikindling effect is discussed, and suggestions for future research are made.

Comparative effects of nonselective and subtype-selective gamma-aminobutyric acidA receptor positive modulators in the rat-conditioned emotional response test

Benzodiazepine receptor anxiolytics show no selectivity between gamma-aminobutyric acid-A receptors containing alpha1, alpha2, alpha3 or alpha5 subunits. Pharmacological studies and data emerging from transgenic mouse models, however, predict that compounds with selective affinity and/or efficacy for gamma-aminobutyric acid-A receptor subtypes would have novel pharmacological profiles. Thus, the gamma-aminobutyric acid-A-alpha1 'affinity selective' drug zolpidem has a sedative-hypnotic profile, whereas L838,417, which has 'selective efficacy' for gamma-aminobutyric acid-A-alpha2, alpha3 and alpha5 receptors, has an anxiolytic-like profile. Here, we compare the nonselective benzodiazepine-site-positive modulators diazepam, lorazepam, midazolam, alprazolam and zopiclone with (i) gamma-aminobutyric acid-AA-alpha1 affinity selective compounds zolpidem and CL218,872 and (ii) L838,417, in the rat-conditioned emotional response test after systemic administration. Given the role of the basolateral amygdala in anxiety and the expression of alpha1, alpha2 and alpha3 subunits in this region, we also assessed the effects of bilateral infusion of L838,417 and midazolam directly into basolateral amygdala in the conditioned emotional response test. Nonselective modulators at low-moderate doses produced anxiolytic effects and sedation at higher doses. Zolpidem was inactive as an anxiolytic and engendered severe sedation, whereas CL218,872 produced an anxiolytic-like profile with minimal sedation. L838,417 produced an anxiolytic-like profile with no sedation, albeit producing behavioural disturbance at high doses. Infusion of midazolam and L838,417 into basolateral amygdala engendered anxiolytic-like effects, although both compounds were more effective after systemic injections, implicating additional brain sites in their anxiolytic-like actions after systemic administration. In conclusion, the diversity of effects of the compounds studied implicates both intrinsic efficacy and/or subtype selectivity as important determinants of anxiolytic-like effects in the rat-conditioned emotional response test.

Anticonvulsants in sports: ethical considerations

OBJECTIVE

Antidoping codes in sport are intended to deter and sanction athletes using performance-enhancing agents while promoting an even playing field for all competitors. Although the World Anti-Doping Code (WADC) permits anticonvulsants in general, harmonization of antidoping permits an international sport federation (IF) to prohibit specific medications within that IF. The anticonvulsants levetiracetam, tiagabine, and lamotrigine may pose ethical dilemmas and could be considered violations of antidoping codes.

METHOD

This study is a literature review with analysis.

RESULTS

Lamotrigine, with antiglutamatergic and sodium channel properties, is FDA-approved for maintenance treatment of bipolar disorder, in addition to its use in the treatment of major depression, anxiety disorders, and schizophrenia. Tiagabine, a selective GABA reuptake inhibitor, has mood-stabilizing and anxiolytic properties. Levetiracetam, whose unique mechanism involves the modulators beta-carboline and zinc, has anxiolytic and mood-stabilizing properties. Anxiolytics, antidepressants, and antipsychotics are banned in archery; under strict liability, all three anticonvulsants violate WADC/IF for that specific sport and could result in disqualification unless therapeutic use exemptions (TUEs) are obtained. Ethical issues regarding the use of anticonvulsants by athletes and the need to obtain TUEs are addressed.

CONCLUSION

The WADC with harmonized IF policies are meant to prevent doping by athletes, but not appropriate medical treatment. When anticonvulsants have other psychotropic properties, ethical issues arise. Athletes should list all medications taken with diagnoses, obtain TUEs as indicated, and contact the appropriate IF or Olympic organization to determine the status of the proposed medication (banned, restricted, nonbanned). Further, clinicians should be knowledgeable regarding these issues when treating athletes.

Dual monoamine modulation for the antidepressant-like effect of lamotrigine in the modified forced swimming test

Lamotrigine is an anticonvulsant drug that exhibits a clinical antidepressant effect. However, few studies have been conducted with lamotrigine in animal models of depression and its mechanism of antidepressant action is still unclear. The present study evaluates the effect of lamotrigine (5-20mg/kg, i.p.) in the modified forced swimming test and compare its behavior pattern in the test with those of paroxetine (20mg/kg, i.p.), nortriptyline (20mg/kg, i.p.) and dizolcipine-MK-801 (0.1mg/kg, i.p.). The effect of lamotrigine on locomotor activity and memory was also studied in order to exclude false-positive results. At low doses, lamotrigine (10mg/kg) decreased immobility and increased climbing scores, a similar pattern to nortriptyline. A higher lamotrigine dose (20mg/kg) also increased swimming scores. Lamotrigine neither changed locomotion in the open-field test nor impaired habituation. Paroxetine and dizolcipine decreased immobility and increased swimming. Dizolcipine also decreased climbing. However, although the effects of paroxetine and nortriptyline were seen without effect on locomotor activity, dizolcipine increased locomotor activity. The present study indicates that the antidepressant-like effect of lamotrigine is probably related to noradrenergic/serotonergic systems.

Picrotoxin blocks the anxiolytic- and panicolytic-like effects of sodium valproate in the rat elevated T-maze

The effect of acute sodium valproate administration, an anxiolytic and putative panicolytic drug, was evaluated in rats tested in the elevated T-maze, an animal model that measures two defensive reactions: avoidance (inhibitory avoidance), related to generalized anxiety, and escape (escape from open arms), related to panic. Additionally, the involvement of gamma-aminobutyric acid (GABA) neurotransmission in sodium valproate effects was studied by picrotoxin co-administration. Sodium valproate (300 mg/kg, intraperitoneally, 30 min before the test) impaired both avoidance latency (time to leave the closed arm) and one-way escape (latency to enter the closed arm) indicating anxiolytic and panicolytic effects, respectively. Pre-treatment with picrotoxin (0.5 mg/kg, intraperitoneally, 5 min before sodium valproate administration) blocked the effects of sodium valproate on inhibitory avoidance and one-way escape. No locomotor effect was seen in the open-field. These data suggest that sodium valproate exerts anxiolytic-like and panicolytic-like effects in the elevated T-maze and that these effects were mediated by picrotoxin-sensitive GABA type A receptors.

Multi-target strategies for the improved treatment of depressive states: Conceptual foundations and neuronal substrates, drug discovery and therapeutic application

Major depression is a debilitating and recurrent disorder with a substantial lifetime risk and a high social cost. Depressed patients generally display co-morbid symptoms, and depression frequently accompanies other serious disorders. Currently available drugs display limited efficacy and a pronounced delay to onset of action, and all provoke distressing side effects. Cloning of the human genome has fuelled expectations that symptomatic treatment may soon become more rapid and effective, and that depressive states may ultimately be "prevented" or "cured". In pursuing these objectives, in particular for genome-derived, non-monoaminergic targets, "specificity" of drug actions is often emphasized. That is, priority is afforded to agents that interact exclusively with a single site hypothesized as critically involved in the pathogenesis and/or control of depression. Certain highly selective drugs may prove effective, and they remain indispensable in the experimental (and clinical) evaluation of the significance of novel mechanisms. However, by analogy to other multifactorial disorders, "multi-target" agents may be better adapted to the improved treatment of depressive states. Support for this contention is garnered from a broad palette of observations, ranging from mechanisms of action of adjunctive drug combinations and electroconvulsive therapy to "network theory" analysis of the etiology and management of depressive states. The review also outlines opportunities to be exploited, and challenges to be addressed, in the discovery and characterization of drugs recognizing multiple targets. Finally, a diversity of multi-target strategies is proposed for the more efficacious and rapid control of core and co-morbid symptoms of depression, together with improved tolerance relative to currently available agents.

Improved bioavailability of the mGlu2/3 receptor agonist LY354740 using a prodrug strategy: in vivo pharmacology of LY544344

Numerous studies have indicated that selective agonists of group II metabotropic glutamate (mGlu) receptors, such as LY354740 [(1S,2S,5R,6S)-2-aminobicyclo[3.1.0]hexane-2,6-dicarboxylate monohydrate] and LY379268 [(-)-2-oxa-4-aminobicyclo[3.1.0]hexane-4,6-dicarboxylate], may be useful in the treatment of many psychiatric disorders, including psychosis, anxiety, and drug withdrawal. Although animal and human studies demonstrate potential therapeutic utility, poor oral bioavailability is a limiting factor in the clinical development of these compounds. Therefore, a novel prodrug approach is being pursued to increase exposure levels of active compound after oral administration. Here, we demonstrate a 10-fold increase in brain, plasma, and cerebrospinal fluid levels of LY354740 after oral prodrug administration. Furthermore, we compare the oral efficacy of the mGlu2/3 receptor agonist LY354740 and its prodrug LY544344 [(1S,2S,5R,6S)-2-[(2'S)-(2'-amino)propionyl]aminobicyclo[3.1.0]hexane-2,6-dicarboxylic acid hydrochloride] in rodent models of psychosis and anxiety. Phencyclidine (PCP)-induced hyperlocomotion was dose dependently inhibited in rats receiving oral administration of 30 or 100 mg/kg LY544344, whereas LY354740 did not significantly reverse PCP-mediated behaviors at doses up to 100 mg/kg. Orally administered LY544344 (30 mg/kg) and subcutaneously administered LY354740 (10 mg/kg) attenuated stress-induced hyperthermia in DBA/2 mice, with the prodrug producing anxiolytic effects at lower oral doses than the parent compound. Although oral administration of LY354740 did not significantly affect fear-induced suppression of operant responding in rats, subcutaneously administered LY354740 (10 or 20 mg/kg) and orally administered LY544344 (10 or 30 mg/kg) produced significant anxiolytic effects in this model. The present data confirm that mGlu2/3 receptor agonists produce antipsychotic and anxiolytic effects in animal behavioral models and demonstrate that oral bioavailability of LY354740 was substantially increased using a prodrug strategy.

A comparison of chlordiazepoxide, bretazenil, L838,417 and zolpidem in a validated mouse Vogel conflict test

RATIONALE

GABAA receptors containing an alpha2 subunit are proposed to mediate the anxiolytic effect of benzodiazepines (BZ) based on studies in transgenic mice using unconditioned models of anxiety. Conditioned models of anxiety were not assessed and are rarely encountered in phenotyping of genetically modified animals. The novel benzodiazepine site ligand L838,417 is a partial agonist at GABAA receptors containing an alpha2, alpha3 or alpha5 subunit and an antagonist at alpha1 receptors, giving an anxiolytic profile devoid of sedation. However, this compound has not previously been assessed in mice.

OBJECTIVES

(1) Establish the Vogel conflict test (VCT) in C57BL/6J mice and validate it with a range of pharmacological tools and (2) compare the full and partial GABAA receptor positive modulators chlordiazepoxide (CDP) and bretazenil (BRZ), respectively, with the subtype selective ligands zolpidem (ZOL; alpha1 selective) and L838,417.

RESULTS

(1) enhanced thirst (water deprivation or isoproterenol administration), analgesia (lamotrigine) or cognitive impairment (MK-801) did not generate false positives in the VCT; (2) CDP and BRZ engendered linear dose-related anti-conflict effects and also increased unpunished drinking; (3) L838,417 engendered a bell-shaped anti-conflict effect and did not increase unpunished drinking; (4) the anti-conflict effect of CDP and L838,417 were antagonised by flumazenil, whereas BRZ's effect was insensitive to this antagonist; and (5) ZOL induced motoric deficits and no anti-conflict effect.

CONCLUSION

We have established the VCT in C57BL/6J mice and validated this test behaviourally, physiologically and pharmacologically. The novel GABAA receptor ligand L838,417 was anxiolytic in this mouse model, and unlike the non-selective compounds, had no effect on unpunished drinking.

Heterozygosity for a protein truncation mutation of sodium channel SCN8A in a patient with cerebellar atrophy, ataxia, and mental retardation

BACKGROUND

The SCN8A gene on chromosome 12q13 encodes the voltage gated sodium channel Na(v)1.6, which is widely expressed in neurons of the CNS and PNS. Mutations in the mouse ortholog of SCN8A result in ataxia and other movement disorders.

METHODS

We screened the 26 coding exons of SCN8A in 151 patients with inherited or sporadic ataxia.

RESULTS

A 2 bp deletion in exon 24 was identified in a 9 year old boy with mental retardation, pancerebellar atrophy, and ataxia. This mutation, Pro1719ArgfsX6, introduces a translation termination codon into the pore loop of domain 4, resulting in removal of the C-terminal cytoplasmic domain and predicted loss of channel function. Three additional heterozygotes in the family exhibit milder cognitive and behavioural deficits including attention deficit hyperactivity disorder (ADHD). No additional occurrences of this mutation were observed in 625 unrelated DNA samples (1250 chromosomes).

CONCLUSIONS

The phenotypes of the heterozygous individuals suggest that mutations in SCN8A may result in motor and cognitive deficits of variable expressivity, but the study was limited by lack of segregation in the small pedigree and incomplete information about family members. Identification of additional families will be required to confirm the contribution of the SCN8A mutation to the clinical features in ataxia, cognition and behaviour disorders.

The role of glutamate in anxiety and related disorders

Anxiety, stress, and trauma-related disorders are a major public health concern in the United States. Drugs that target the gamma-aminobutyric acid or serotonergic system, such as benzodiazepines and selective serotonin reuptake inhibitors, respectively, are the most widely prescribed treatments for these disorders. However, the role of glutamate in anxiety disorders is becoming more recognized with the belief that drugs that modulate glutamatergic function through either ionotropic or metabotropic glutamate receptors have the potential to improve the current treatment of these severe and disabling illnesses. Animal models of fear and anxiety have provided a method to study the role of glutamate in anxiety. This research has demonstrated that drugs that alter glutamate transmission have potential anxiolytic action for many different paradigms including fear-potentiated startle, punished responding, and the elevated plus maze. Human clinical drug trials have demonstrated the efficacy of glutamatergic drugs for the treatment of obsessive-compulsive disorder, posttraumatic stress disorder, generalized anxiety disorder, and social phobia. Recent data from magnetic resonance imaging studies provide an additional link between the glutamate system and anxiety. Collectively, the data suggest that future studies on the mechanism of and clinical efficacy of glutamatergic agents in anxiety disorders are appropriately warranted.