Pregabalin action at a model synapse: Binding to presynaptic calcium channel α2-δ subunit reduces neurotransmission in mice

The effect of oral pregabalin on the minimum alveolar concentration of isoflurane in cats

OBJECTIVE

To investigate the effect of three different doses of oral pregabalin on minimum alveolar concentration of isoflurane (MACISO) in cats.

STUDY DESIGN

Prospective, randomized, placebo-controlled, blinded, crossover trial.

ANIMALS

A group of eight healthy adult cats aged 24-48 months.

METHODS

Cats were randomly assigned to three oral doses of pregabalin (low dose: 2.5 mg kg-1, medium dose: 5 mg kg-1, high dose: 10 mg kg-1) or placebo 2 hours before MACISO determination, with the multiple treatments administered with a minimum 7 day washout period. Anesthesia was induced and maintained with isoflurane in oxygen until endotracheal intubation was achieved, and maintained with isoflurane with volume-controlled ventilation. MACISO was determined in triplicate using the bracketing technique and tail clamp method 120 minutes after pregabalin or placebo administration. Physiologic variables (including heart rate and blood pressure) recorded during MACISO determination were averaged and compared between the pregabalin and placebo treatments. One-way analysis of variance and the Friedman test were used to assess the difference for normally and non-normally distributed data, respectively. The Tukey test was used as a post hoc analysis. Values of p < 0.05 were considered significant.

RESULTS

The MACISO with the medium- and high-dose pregabalin treatments were 1.33 ± 0.21% and 1.23 ± 0.17%, respectively. These were significantly lower than MACISO after placebo treatment (1.62 ± 0.13%; p = 0.014, p < 0.001, respectively), representing a decrease of 18 ± 9% and 24 ± 6%. The mean plasma pregabalin concentration was negatively correlated with MACISO values. Physiologic variables did not differ significantly between treatments.

CONCLUSIONS AND CLINICAL RELEVANCE

Doses of 5 or 10 mg kg-1 pregabalin, administered orally 2 hours before determining MACISO, had a significant isoflurane-sparing effect in cats.

Evaluating the Effect of Pregabalin in the Treatment of Carpal Tunnel Syndrome: A Prospective, Randomized, Triple-Blinded, Placebo-controlled Trial

OBJECTIVE

This study aimed to determine the effectiveness of pregabalin for the control of symptoms in mild to moderate idiopathic Carpal tunnel syndrome (CTS).

METHODS

In this randomized, placebo-controlled trial, 146 mild to moderate idiopathic CTS patients were randomized into pregabalin (n=74) and placebo groups (n=72). Per protocol, analysis was conducted with 131 patients; pregabalin (n=65) and placebo (n=66). The drug titration dose was 50 mg once daily for the first week, twice daily for the second week and thrice daily for the next 6 weeks. The primary outcome included a change in the Symptom Severity Scale and Functional Status Scale (FSS) of the Boston Carpal Tunnel Questionnaire after the eighth week. The secondary outcome was the change in clinical and electrophysiological grading after 8 weeks of therapy.

RESULTS

There was a statistically significant improvement in the mean Symptom Severity Scale (14.92±3.72 vs. 16.55±4.45; P =0.025) and FSS (10.77±2.64 vs. 12.0±2.55; P =0.007) in the pregabalin group after 8 weeks. Mean clinical and electrophysiological grading changed significantly from 2.3±0.7 to 2.1±0.8 ( P =0.001) and 1.9±0.7 to 1.8±0.8 ( P =0.020), respectively in the pregabalin group but not in the placebo group.

DISCUSSION

The results of this study demonstrates that pregabalin is effective in ameliorating symptoms and improving functional outcomes in mild to moderate idiopathic CTS.

Pregabalin synchronizes the regeneration of nerve and muscle fibers optimizing the gait recovery of MDX dystrophic mice

Duchenne muscular dystrophy (DMD) is an X-linked genetic disorder induced by mutations in the dystrophin gene, leading to a degeneration of muscle fibers, triggering retrograde immunomodulatory, and degenerative events in the central nervous system. Thus, neuroprotective drugs such as pregabalin (PGB) can improve motor function by modulating plasticity, together with anti-inflammatory effects. The present work aimed to study the effects of PGB on axonal regeneration after axotomy in dystrophic and non-dystrophic mice. For that, MDX and C57BL/10 mouse strains were subjected to peripheral nerve damage and were treated with PGB (30 mg/kg/day, i.p.) for 28 consecutive days. The treatment was carried out in mice as soon as they completed 5 weeks of life, 1 week before the lesion, corresponding to the peak period of muscle degeneration in the MDX strain. Six-week-old mice were submitted to unilateral sciatic nerve crush and were sacrificed in the 9th week of age. The ipsi and contralateral sciatic nerves were processed for immunohistochemistry and qRT-PCR, evaluating the expression of proteins and gene transcripts related to neuronal and Schwann cell activity. Cranial tibial muscles were dissected for evaluation of neuromuscular junctions using α-bungarotoxin, and the myelinated axons of the sciatic nerve were analyzed by morphometry. The recovery of motor function was monitored throughout the treatment through tests of forced locomotion (rotarod) and spontaneous walking track test (Catwalk system). The results show that treatment with PGB reduced the retrograde cyclic effects of muscle degeneration/regeneration on the nervous system. This fact was confirmed after peripheral nerve injury, showing better adaptation and response of neurons and glia for rapid axonal regeneration, with efficient muscle targeting and regain of function. No side effects of PGB treatment were observed, and the expression of pro-regenerative proteins in neurons and Schwann cells was upregulated. Morphometry of the axons was in line with the preservation of motor endplates, resulting in enhanced performance of dystrophic animals. Overall, the present data indicate that pregabalin is protective and enhances regeneration of the SNP during the development of DMD, improving motor function, which can, in turn, be translated to the clinic.

The Effect of Pregabalin on the Minimum Alveolar Concentration of Sevoflurane: A Randomized, Placebo-Controlled, Double-Blind Clinical Trial

Background

Pregabalin is commonly used perioperatively to reduce post-operative pain and opioid consumption and to prevent the development of chronic pain. It has been shown to reduce anesthetic consumption in balanced anesthesia, but studies investigating its effect on the minimum alveolar concentration (MAC) of volatile anesthetics are lacking. The aim of this study was to investigate the effect of two different doses of pregabalin on the MAC of sevoflurane.

Methods

In a randomized, double-blinded, placebo controlled clinical study, 75 patients were assigned to receive placebo, 300 mg pregabalin, or 150 mg pregabalin, as a capsule 1 h before anesthesia induction with sevoflurane only. After equilibration, the response to skin incision (movement vs. non-movement) was monitored. The MAC was assessed using an up- and down-titration method.

Results

The MAC of sevoflurane was estimated as 2.16% (95% CI, 2.07–2.32%) in the placebo group, 1.44% (95% CI, 1.26–1.70%) in the 300 mg pregabalin group, and 1.81% (95% CI, 1.49–2.13%) in the 150 mg pregabalin group. We therefore report a 33% reduction in the MAC of sevoflurane in the 300 mg pregabalin group as compared to placebo. The MAC of the 150 mg pregabalin group was reduced by 16% as compared to placebo but was not statistically significant.

Conclusions

The administration of 300 mg pregabalin reduced the MAC of sevoflurane by 33%, while the administration of 150 mg pregabalin did not significantly reduce the MAC of sevoflurane. Pregabalin use led to a small reduction in post-operative pain levels but increased side effects in a dose-dependent manner.

The teratogenic effect of pregabalin on heart, liver and kidney in rats: a light microscopic, electron microscopic and immunohistochemical study

BACKGROUND

Pregabalin (PGB) was approved as new anti-epileptic drugs with little information about its teratogenic effect.

AIM OF THE WORK

to evaluate the developmental toxicity of PGB.

MATERIALS AND METHODS

60 pregnant albino rats were divided into three groups. PGB (500 mg/kg body weight/day) was given to group II, PGB (1250 mg/kg body weight/day) was given to Group III and no medications were given to group I. The pups were normally delivered. Liver, kidney and heart specimens were prepared for histological, immunohistochemical, and morphometric studies.

RESULTS

A dose of 500 mg of PGB had minimal toxic effects in the form of mild collagen deposition and moderate positive caspase-3 immunoexpression. PGB dose of 1250 mg/kg induced gross toxic effects in form of degenerated cardiac myofibres, ruptured blood vessels, vacuolations in the renal cortex, fibrosis and strong positive caspase-3 immunoexpression.

CONCLUSION

PGB at dose of 500 mg/kg revealed minimal toxic changes. PGB cause embryotoxicity in a dose-dependent manner, as the higher dose induced more degenerative changes.

Why It Is Important to Consider the Effects of Analgesics on Sleep: A Critical Review

We review the known physiological mechanisms underpinning all of pain processing, sleep regulation, and pharmacology of analgesics prescribed for chronic pain. In particular, we describe how commonly prescribed analgesics act in sleep-wake neural pathways, with potential unintended impact on sleep and/or wake function. Sleep disruption, whether pain- or drug-induced, negatively impacts quality of life, mental and physical health. In the context of chronic pain, poor sleep quality heightens pain sensitivity and may affect analgesic function, potentially resulting in further analgesic need. Clinicians already have to consider factors including efficacy, abuse potential, and likely side effects when making analgesic prescribing choices. We propose that analgesic-related sleep disruption should also be considered. The neurochemical mechanisms underlying the reciprocal relationship between pain and sleep are poorly understood, and studies investigating sleep in those with specific chronic pain conditions (including those with comorbidities) are lacking. We emphasize the importance of further work to clarify the effects (intended and unintended) of each analgesic class to inform personalized treatment decisions in patients with chronic pain. © 2021 American Physiological Society. Compr Physiol 11:1-31, 2021.

Pharmacokinetics of a New, Once-Daily, Sustained-Release Pregabalin Tablet in Healthy Male Volunteers

PURPOSE

A new sustained-release (SR) pregabalin formulation (YHD1119) designed for once-daily dosing has recently been developed to improve patient adherence. This study aimed to compare the pharmacokinetics of pregabalin SR and immediate-release (IR) formulations after multiple oral doses and to assess the effect of food on the pharmacokinetic profile of the pregabalin SR formulation after a single dose in healthy individuals.

METHODS

Two clinical trials were conducted: a randomized, open-label, multiple-dose, 2-treatment, 2-period crossover study to evaluate the steady-state pharmacokinetic properties of SR treatment (pregabalin SR 300 mg once daily for 3 days) and IR treatment (pregabalin IR 150 mg twice daily for 3 days) under fed conditions and a randomized, open-label, single-dose, 2-treatment, 2-period, crossover study to evaluate the effect of food intake on the pharmacokinetic properties of the pregabalin SR formulation. Plasma concentrations of pregabalin were measured using LC-MS/MS. The AUC and C_max for pregabalin were calculated using noncompartmental method and compared between treatments in each study.

FINDINGS

Thirty-one individuals in the bioequivalence study and 23 in the food effect study completed the pharmacokinetic sampling. The geometric mean ratios of C_max,ss and AUC_0-τ between the SR and IR formulations were 1.1642 (90% CI, 1.1043-1.2272) and 0.9704 (90% CI, 0.9372-1.0047), respectively. The geometric mean ratios of C_max and AUC_0-last between the SR formulation in the fed state and in the fasted state were 1.6514 (90% CI, 1.3820-1.9732) and 1.7899 (90%CI, 1.4499-2.2097), respectively.

IMPLICATIONS

The bioavailability of the pregabalin SR 300 mg formulation is increased if taken with a high-fat meal. Once-daily pregabalin SR 300 mg is bioequivalent to twice-daily pregabalin IR 150 mg under fed conditions at steady state. The pregabalin SR formulation is expected to improve patient adherence. ClinicalTrials.gov identifiers: NCT02783183 (bioequivalence study) and NCT03191136 (food effect study).

Ion Channels as New Attractive Targets to Improve Re-Myelination Processes in the Brain

Multiple sclerosis (MS) is the most demyelinating disease of the central nervous system (CNS) characterized by neuroinflammation. Oligodendrocyte progenitor cells (OPCs) are cycling cells in the developing and adult CNS that, under demyelinating conditions, migrate to the site of lesions and differentiate into mature oligodendrocytes to remyelinate damaged axons. However, this process fails during disease chronicization due to impaired OPC differentiation. Moreover, OPCs are crucial players in neuro-glial communication as they receive synaptic inputs from neurons and express ion channels and neurotransmitter/neuromodulator receptors that control their maturation. Ion channels are recognized as attractive therapeutic targets, and indeed ligand-gated and voltage-gated channels can both be found among the top five pharmaceutical target groups of FDA-approved agents. Their modulation ameliorates some of the symptoms of MS and improves the outcome of related animal models. However, the exact mechanism of action of ion-channel targeting compounds is often still unclear due to the wide expression of these channels on neurons, glia, and infiltrating immune cells. The present review summarizes recent findings in the field to get further insights into physio-pathophysiological processes and possible therapeutic mechanisms of drug actions.

[Pregabalin abuse and dependence in various European countries: Association with substitution policies]

INTRODUCTION

Pregabalin was first approved in 2004 for the treatment of peripheral neuropathic pain and focal epileptic seizures, with or without secondary generalization. Prescription frequency has increased significantly since approval. In the early days, little attention was paid to the problem of misuse and dependence on pregabalin; in recent years, there has been a significant increase in the number of publications focusing on this problem. This review deals with these risk factors and risk groups of pregabalin abuse and dependence in different European countries and their drug policies.

RESULTS

Pregabalin abuse and dependence has increased significantly since its introduction to the market. It was shown that solo abuse of pregabalin is rare. In most cases, pregabalin was combined with other substances, which is also a predictor of pregabalin abuse. There were different reasons for the non-prescription use of pregabalin; it was used to increase the psychotropic effect, on the one hand, and to alleviate withdrawal symptoms, on the other hand. Furthermore, in Sweden, pregabalin was found in 28% of fatal intoxications among drug addicts. Young people were particularly affected. Abuse of pregabalin was detected in countries with restrictive substitution programmes, while in countries with liberal drug policies, no abuse was detected. However, the data situation in Switzerland with a liberal substitution programme is based on only one study, which is why pregabalin use in liberal substitution programmes cannot be conclusively clarified.

CONCLUSIONS

There seems to be a connection between a country's drug policy and the illegal use of pregabalin among persons in a substitution programme in that country. There are also risk factors and risk groups for pregabalin dependence and abuse.

Neuroprotective Methodologies of Co-Enzyme Q10 Mediated Brain Hemorrhagic Treatment: Clinical and Pre-Clinical Findings

Cerebral brain hemorrhage is associated with the highest mortality and morbidity despite only constituting approximately 10-15% of all strokes classified into intracerebral and intraventricular hemorrhage where most of the patients suffer from impairment in memory, weakness or paralysis in arms or legs, headache, fatigue, gait abnormality and cognitive dysfunctions. Understanding molecular pathology and finding the worsening cause of hemorrhage will lead to explore the therapeutic interventions that could prevent and cure the disease. Mitochondrial ETC-complexes dysfunction has been found to increase neuroinflammatory cytokines, oxidative free radicals, excitotoxicity, neurotransmitter and energy imbalance that are the key neuropathological hallmarks of cerebral hemorrhage. Coenzyme Q10 (CoQ10), as a part of the mitochondrial respiratory chain can effectively restore these neuronal dysfunctions by preventing the opening of mitochondrial membrane transition pore, thereby counteracting cell death events as well as exerts an anti-inflammatory effect by influencing the expression of NF-kB1 dependent genes thus preventing the neuroinflammation and energy restoration. Due to behavior and biochemical heterogeneity in post cerebral brain hemorrhagic pattern different preclinical autologous blood injection models are required to precisely investigate the forthcoming therapeutic strategies. Despite emerging pre-clinical research and resultant large clinical trials for promising symptomatic treatments, there are very less pharmacological interventions demonstrated to improve post operative condition of patients where intensive care is required. Therefore, in current review, we explore the disease pattern, clinical and pre-clinical interventions under investigation and neuroprotective methodologies of CoQ10 precursors to ameliorate post brain hemorrhagic conditions.

Prenatal pregabalin is associated with sex-dependent alterations in some behavioral parameters in valproic acid-induced autism in rat offspring

This study was performed to evaluate the effects of prenatal exposure to pregabalin (PGB) on behavioral changes of rat offspring in an animal model of valproic acid (VPA)-induced autism-like symptoms. Pregnant rats received VPA (600 mg/kg/i.p.) once at 12.5 gestational days for autism-like symptom induction in offspring. After the delivery single male and single female offspring from each mother were randomly selected for behavioral test (anxiety, pain response, pleasure, and motor function) at 60th day adulthood (n = 7). Offspring received prenatal PGB (15 & 30 mg/kg/i.p.) during gestational days 9.5 to 15.5 either alone or in combination with VPA (PGB15, PGB30, PGB15 + VPA, and PGB30 + VPA). Control offspring received normal saline during the same period. The result showed that prenatal VPA exposure was associated with autism-like behaviors in rat offspring. PGB treatment during the gestational period revealed significant reduction in sucrose preference test and anxiety in elevated plus maze and open field test in offspring. Also, PGB treatments exhibited a dose-dependent increase in pain threshold in prenatally VPA exposed rats in tail-flick and hot plate test. Also, there was a sex-related significant impairment in motor function in beam balance and open field test, and male rats were affected more than females. However, no significant sex differences in sucrose preference and pain sensitivity were observed in prenatal PGB-treated rat offspring. In conclusion, prenatal exposure to VPA increased the risk of autism-like behaviors in the offspring rats, and PGB treatment during the gestational period was associated with some beneficial effects, including anxiety reduction and motor impairment in autism-like symptoms in rat offspring.

Pregabalin affords retinal neuroprotection in diabetic rats: Suppression of retinal glutamate, microglia cell expression and apoptotic cell death

Pregabalin is the first drug to receive FDA approval for treating diabetic neuropathic pain. This study investigated the neuroprotective effect of pregabalin in an experimental model of diabetic retinopathy and tested some possible mechanisms underlying the putative neuroprotective effect. Male Wistar rats received streptozotocin (45 mg/kg) to induce type 1 diabetes mellitus. After two weeks, a course of pregabalin (3, 10 and 30 mg/kg) has been launched for five consecutive weeks. Retinal expression of interleukin-1β (IL-1β) and tumor necrosis factor-α (TNF-α) was estimated by real-time PCR and retinal glutamate content was also estimated. Further, retinal caspase-3 immunoblotting and DNA fragmentation assays determined the degree of apoptosis. Pregabalin improved histopathological abnormalities in diabetic retinas and suppressed the diabetes-enhanced retinal expression of IL-1β, TNF-α, CD₁₁b (a surface marker for microglia) while attenuated expression of caspase-3 and DNA fragmentation versus the diabetic group. In addition, diabetic rats treated with pregabalin displayed reductions in retinal glutamate, nitric oxide and malondialdehyde (MDA) and enhanced reduced glutathione (GSH) content versus the diabetic controls. Furthermore, pregabalin enhanced the histopathological picture and reduced fibrosis in the optic nerve of diabetic rats in addition to suppression of the content of the glia fibrillary acidic protein. The findings provide the first evidence demonstrating that pregabalin alleviates retinal neuroinflammation, apoptosis and oxidative stress in an experimental type 1 diabetes mellitus. Therefore, pregabalin might serve as a potential therapy for retinopathy after adequate clinical research.

Systems genetic and pharmacological analysis identifies candidate genes underlying mechanosensation in the von Frey test

Mechanical sensitivity is commonly affected in chronic pain and other neurological disorders. To discover mechanisms of individual differences in punctate mechanosensation, we performed quantitative trait locus (QTL) mapping of the response to von Frey monofilament stimulation in BXD recombinant inbred (BXD) mice. Significant loci were detected on mouse chromosome (Chr) 5 and 15, indicating the location of underlying polymorphisms that cause heritable variation in von Frey response. Convergent evidence from public gene expression data implicates candidate genes within the loci: von Frey thresholds were strongly correlated with baseline expression of Cacna2d1, Ift27 and Csnk1e in multiple brain regions of BXD strains. Systemic gabapentin and PF-670462, which target the protein products of Cacna2d1 and Csnk1e, respectively, significantly increased von Frey thresholds in a genotype-dependent manner in progenitors and BXD strains. Real-time polymerase chain reaction confirmed differential expression of Cacna2d1 and Csnk1e in multiple brain regions in progenitors and showed differential expression of Cacna2d1 and Csnk1e in the dorsal root ganglia of the progenitors and BXD strains grouped by QTL genotype. Thus, linkage mapping, transcript covariance and pharmacological testing suggest that genetic variation affecting Cacna2d1 and Csnk1e may contribute to individual differences in von Frey filament response. This study implicates Cacna2d1 and Ift27 in basal mechanosensation in line with their previously suspected role in mechanical hypersensitivity. Csnk1e is implicated for von Frey response for the first time. Further investigation is warranted to identify the specific polymorphisms involved and assess the relevance of these findings to clinical conditions of disturbed mechanosensation.

Effect of pregabalin administration upon reperfusion in a rat model of hyperglycemic stroke: Mechanistic insights associated with high-mobility group box 1

Hyperglycemia, which reduces the efficacy of treatments and worsens clinical outcomes, is common in stroke. Ability of pregabalin to reduce neuroexcitotoxicity may provide protection against stroke, even under hyperglycemia. We investigated its protective effect against hyperglycemic stroke and its possible molecular mechanisms. Male Wistar rats administered dextrose to cause hyperglycemia, underwent middle cerebral artery occlusion for 1 h and subsequent reperfusion. Rats were treated with an intraperitoneal injection of 30 mg/kg pregabalin or an equal amount of normal saline at the onset of reperfusion (n = 16 per group). At 24 h after reperfusion, neurological deficit, infarct volume, and apoptotic cell count were assessed. Western blot analysis was performed to determine protein expression of high-mobility group box 1 (HMGB1), toll-like receptor-4 (TLR-4), phosphorylated nuclear factor-kappa B (p-NF-κB), interleukin-1beta (IL-1β), tumor necrosis factor-alpha (TNF-α), phosphorylated inducible and endothelial nitric oxide synthase (p-iNOS, p-eNOS), Bcl-2, Bax, Cytochrome C, and caspase-3 in the brain. Pregabalin-treated rats showed significantly improved neurological function (31% decrease in score), reduced infarct size (by 33%), fewer apoptotic cells (by 63%), and lower expression levels of HMGB1, TLR4, p-NF-κB, IL-1β, and TNF- α, compared with control rats. Decreased p-iNOS and increased p-eNOS expressions were also observed. Expression of Bax, Cytochrome C, and cleaved caspase-3/caspase3 was significantly downregulated, while Bcl-2 expression was increased by pregabalin treatment. Pregabalin administration upon reperfusion decreased neuronal death and improved neurological function in hyperglycemic stroke rats. Cogent mechanisms would include attenuation of HMGB1/TLR-4-mediated inflammation and favorable modulation of the NOS.

The influence of thiamin on the efficacy of pregabalin in rats with spinal nerve ligation (SNL)-induced neuropathic pain

OBJECTIVE

The thiamin is often used in the treatment of neuropathy, and pregabalin is often used to treat neuropathic pain. Our study examined the influence of thiamin on the efficacy of pregabalin in a rat model of spinal nerve ligation (SNL)-induced neuropathic pain.

METHODS

Sprague-Dawley male rats were randomly divided into six groups. The neuropathic pain-relieving properties were measured by plantar test, cold plate test, and hot plate test after administration of pregabalin (i.v) and/or thiamin (i.p) in SNL rats 14 days after operation.

RESULTS

In the therapy period, pregabalin, or thiamin alone all produced antinociceptive effects in rats with neuropathic pain. And combination treatment of thiamin and pregabalin resulted in an enhanced pain relief compared to the administration of pregabalin or thiamin alone.

CONCLUSION

Combination of thiamin and pregabalin produces an additive antinociceptive effect in neuropathic pain rats, this drug combination may offer a beneficial treatment option for neuropathic pain.

Neuropathic Pain due to Small Fiber Neuropathy in Aging: Current Management and Future Prospects

Over the last 10 years, the diagnosis small fiber neuropathy (SFN) has gained recognition worldwide. Patients often suffer from severe neuropathic pain that may be difficult to treat. A substantial subset of patients with SFN is aged 65 years or older, and these patients often exhibit comorbidities and usage of multiple drugs, making neuropathic pain treatment more challenging. In this review, we highlight relevant pathophysiological aspects and discuss currently used therapeutic strategies for neuropathic pain. Possible pitfalls in neuropathic pain treatment in the elderly will be underlined.

Neuropsychiatric symptoms accompanying thrombocytopenia following pregabalin treatment for neuralgia: a case report

CASE DESCRIPTION

A 28-year-old female patient developed an increased temperature and neuropsychiatric symptoms after receiving 75 mg pregabalin therapy for neuralgia. She presented initially with pyrexia and dizziness, followed by disorganized speech within an acute confusional state. Her body temperature returned to normal after taking 60 mg loxoprofen sodium several hours later. However, the neuropsychiatric symptoms did not improve until the next morning. Routine blood tests showed decreased platelet counts (from 131 × 109/L to 85 × 109/L). The following day, a further dose of 75 mg pregabalin was administered because of its effective amelioration of the patient's neuralgia. One hour later, the same symptoms appeared as had previously including increased body temperature of 39.2 °C accompanied by a lower platelet count (73 × 109/L).

CONCLUSION

Clinicians should be alert to the serious neuropsychiatric symptoms and thrombocytopenia associated with the use of pregabalin. Routine blood tests may be necessary upon initiation of pregabalin treatment.

Impact of pregabalin treatment on synaptic plasticity and glial reactivity during the course of experimental autoimmune encephalomyelitis

BACKGROUND

Multiple sclerosis (MS) is an autoimmune and neurodegenerative disease that affects young adults. It is characterized by generating a chronic demyelinating autoimmune inflammation in the central nervous system. An experimental model for studying MS is the experimental autoimmune encephalomyelitis (EAE), induced by immunization with antigenic proteins from myelin.

AIMS

The present study investigated the evolution of EAE in pregabalin treated animals up to the remission phase.

METHODS AND RESULTS

The results demonstrated a delay in the onset of the disease with statistical differences at the 10th and the 16th day after immunization. Additionally, the walking track test (CatWalk) was used to evaluate different parameters related to motor function. Although no difference between groups was obtained for the foot print pressure, the regularity index was improved post treatment, indicating a better motor coordination. The immunohistochemical analysis of putative synapse preservation and glial reactivity revealed that pregabalin treatment improved the overall morphology of the spinal cord. A preservation of circuits was depicted and the glial reaction was downregulated during the course of the disease. qRT-PCR data did not show immunomodulatory effects of pregabalin, indicating that the positive effects were restricted to the CNS environment.

CONCLUSIONS

Overall, the present data indicate that pregabalin is efficient for reducing the seriousness of EAE, delaying its course as well as reducing synaptic loss and astroglial reaction.

Long-term maintenance of response across multiple fibromyalgia symptom domains in a randomized withdrawal study of pregabalin

OBJECTIVE

To determine the incidence and duration of response of clinically meaningful improvements with pregabalin across several key symptoms of fibromyalgia (FM).

METHODS

This was a post hoc analysis of data from a multicenter, double-blind, placebo-controlled, randomized, withdrawal study, originally designed to evaluate the efficacy of pregabalin monotherapy for durability of effect on FM pain based on pain and Patient Global Impression of Change (PGIC) criteria. Responder criteria for Fibromyalgia Impact Questionnaire total score (≥16-point change), Medical Outcomes Study Sleep Scale Sleep Disturbance subscale (≥15.8-point change), and the 36-item Short-Form Health Survey Vitality scale (≥10-point change) were used to evaluate the incidence and duration of improvements in function, sleep, and fatigue for pregabalin versus placebo among pain and PGIC responders. A composite responder index consisting of pain, PGIC, function, and sleep endpoints was used to explore multidimensional response.

RESULTS

Approximately 80% of patients meeting pain and PGIC improvement criteria at randomization had clinically meaningful improvement in fatigue, sleep, or function. Higher proportions of patients in the pregabalin group maintained a clinically meaningful response, and pregabalin-treated patients had a significantly longer time to loss of therapeutic response compared with the placebo group. Composite responder Kaplan-Meier analysis, performed with patients demonstrating clinically meaningful improvements in pain, PGIC, function, and sleep at randomization showed a significantly longer median time to loss of therapeutic response for pregabalin-treated patients.

DISCUSSION

The results from this post hoc analysis indicate that pregabalin provides long-term effects across multiple domains of FM (ClinicalTrials.gov registry ID: NCT00151489).

Effects of pregabalin on the activity of glutamate transporter type 3

BACKGROUND

Pregabalin, (S)-3-aminomethyl-5-methyl hexanoic acid, is a ligand for the α2δ subunit (a component of voltage-gated calcium channels) and has analgesic and anticonvulsant properties. Glutamate uptake by glutamate transporters may be a mechanism for these properties. We investigated the effects of pregabalin on the activity of the neuronal glutamate transporter type 3 (EAAT3).

METHODS

EAAT3 was expressed in Xenopus laevis oocytes. Two-electrode voltage clamping was used to record membrane currents before, during, and after applying l-glutamate (30 μM) in the presence or absence of pregabalin. Currents were also measured in oocytes pretreated with a protein kinase C (PKC) activator (phorbol-12-myristate-13-acetate, PMA), PKC inhibitors (chelerythrine or staurosporine), or a phosphatidylinositol-3-kinase (PI3K) inhibitor wortmannin.

RESULTS

The exposure of the oocytes injected with EAAT3 mRNA to serial concentrations of pregabalin (0.06-60 μM) significantly increased their responses to 30 μM l-glutamate. A kinetic study showed that pregabalin significantly increased V(max) without changing K(m). Treatment of oocytes with PMA, pregabalin, or pregabalin plus PMA significantly increased transporter currents vs controls, but treatment with PMA plus pregabalin did not increase the responses further vs PMA or pregabalin alone. In addition, pretreatment of oocytes with two PKC inhibitors (chelerythrine or staurosporine), or inhibitor wortmannin, significantly reduced basal and pregabalin-enhanced EAAT3 activity.

CONCLUSIONS

Pregabalin increased EAAT3 activity and PKC and PI3K were involved. This may explain the analgesic effect of pregabalin in neuropathic pain.

Effect of the anticonvulsant medications pregabalin and lamotrigine on urodynamic parameters in an animal model of neurogenic detrusor overactivity

AIMS

To assess the effects of different doses and treatment durations of pregabalin and lamotrigine on the urodynamic parameters of an animal model of neurogenic detrusor overactivity (NDO).

MATERIALS AND METHODS

Ninety rats were used; six as normal controls and the remaining 84 were divided as follows: Six "paraplegic controls," 6 "paraplegic-vehicle controls," and the remaining 72 divided into two equal groups. Group 1 was divided into six subgroups; pregabalin was given in doses of 10 mg/kg, 20 mg/kg, or 30 mg/kg for 1 or 2 weeks. Group 2 was similarly subdivided; lamotrigine was given in doses of 1.5 mg/kg, 3 mg/kg, or 6 mg/kg for 1 or 2 weeks.

RESULTS

All paraplegic controls developed NDO within 3 weeks from spinalization. Their baseline bladder pressure (BBP) 19 ± 4.4 cmH(2) O, detrusor pressure at maximum capacity (DPMaxC) 47.6 ± 4.3 cmH(2) O, bladder capacity (BC) 0.45 ± 0.1 ml, and frequency of detrusor overactivity (FDO) 3.7 ± 0.9/min. Both pregabalin and lamotrigine produced significant improvement. Urodynamic values in those treated with 20 mg pregabalin for 1 or 2 weeks were: BBP 11.7 ± 1.3 and 9 ± 0.2 cmH(2) O, BC 0.6 ± 0.1 and 0.7 ± 0.01 ml, DPMaxC 17.3 ± 4.0 and 23 ± 2.6 cmH(2) O, FDO 2.1 ± 0.2/min and 1.7 ± 0.1/min. Urodynamic values in those treated with 3 mg/kg lamotrigine for 1 or 2 weeks were: BBP 9.7 ± 2.2 and 8.6 ± 1.9 cmH(2) O, DPMaxC 17.2 ± 1.8 and 29 ± 1.2 cmH(2) O, BC 0.7 ± 0.1 and 0.8 ± 0.1 ml, FDO 1.9 ± 0.2/min and 1.9 ± 0.2/min (P < 0.001).

CONCLUSIONS

Pregabalin and lamotrigine may represent novel alternative treatments of NDO. Clinical trials remain to be performed.

Mechanisms of pain transmission and pharmacologic management

BACKGROUND

Pain sensation involves multiple signaling and modulatory pathways, employing a variety of neurotransmitters and other mediators. Inhibitory and facilitatory mechanisms affect the perception of stimuli as painful or non-painful, and in addition may affect the perceived intensity of pain. Endogenous opioids are key mediators in the descending pain suppression pathways. Additionally, monoaminergic neurotransmitters such as norepinephrine, serotonin and dopamine positively or negatively modulate pain signaling, depending on receptor type and location. The various mediators involved in pain signaling provide potential targets for pharmacological interventions. Single analgesic therapies may be limited in their ability to comprehensively target these complex pain signaling pathways. Therapeutic approaches acting on multiple pain transmission pathways through different mechanisms of action provide an opportunity to maximize efficacy and tolerability in the treatment of pain.

SCOPE

This article discusses the various physiologic processes involved in pain signaling and modulation, describes the mechanisms by which various classes of analgesic agents are believed to produce their clinical effects, and explores the potential benefits of a multiple-mechanism approach to analgesia. Published articles describing the physiologic processes involved in pain signaling and modulation and the mechanisms of analgesia for different drug classes were reviewed. MEDLINE searches were conducted to identify relevant studies published through August 2009 that evaluated the efficacy and tolerability of multiple-mechanism analgesic regimens. English language-only randomized controlled trials and meta-analyses of randomized controlled trials were considered.

FINDINGS/CONCLUSION

Multiple neurotransmitters and other mediators are involved in the endogenous modulation of pain signaling, providing numerous opportunities for intervention with different classes of analgesics. Data from numerous clinical trials indicate that multiple-mechanism approaches to analgesia provide comparable or superior analgesic efficacy with lower doses of the individual agents and reduced incidence of side effects. These data support current guidelines which endorse multiple-mechanism strategies for both acute and chronic pain management.

Participation of K(ATP) Channels in the Antinociceptive Effect of Pregabalin in Rat Formalin Test

Background

Pregabalin is an anticonvulsant and analgesic agent that interacts selectively with the voltage-sensitive-Ca²⁺-channel alpha-2-delta subunit. The aim of this study was to evaluate whether the analgesic action of intrathecal (IT) pregabalin is associated with K_ATP channels in the rat formalin test.

Methods

IT PE-10 catheters were implanted in male Sprague-Dawley rats (250-300 g) under inhalation anesthesia using enflurane. Nociceptive behavior was defined as the number of hind paw flinches during 60 min after formalin injection. Ten min before formalin injection, IT drug treatments were divided into 3 groups: normal saline (NS) 20 µl (CON group); pregabalin 0.3, 1, 3 and 10 µg in NS 10 µl (PGB group); glibenclamide 100 µg in DMSO 5 µl with pregabalin 0.3, 1, 3 and 10 µg in NS 5 µl (GBC group). All the drugs were flushed with NS 10 µl. Immunohistochemistry for the K_ATP channel was done with a different set of rats divided into naïve, NS and PGB groups.

Results

IT pregabalin dose-dependently decreased the flinching number only in phase 2 of formalin test. The log dose response curve of the GBC group shifted to the right with respect to that of the PGB group. Immunohistochemistry for the K_ATP channel expression on the spinal cord dorsal horn showed no difference among the groups 1 hr after the formalin test.

Conclusions

The antinociceptive effect of pregabalin in the rat formalin test was associated with the activation of the K_ATP channel. However, pregabalin did not induce K_ATP channel expression in the spinal cord dorsal horn.

Pregabalin modulation of spinal and brainstem visceral nociceptive processing

Brainstem and spinal mechanisms mediating visceral nociception are investigated here using electrophysiology and immunohistochemistry techniques in a model of acute visceral pain. Colorectal distension (CRD) produced graded visceromotor responses (VMR) in normal rats, and these were facilitated by intracolonic mustard oil (MO) that generated acute visceral hyperalgesia. The neuropathic pain drug pregabalin (PGB) is thought to have state-dependent effects in attenuating neuropathic, but not acute somatic pain, likely by impairing calcium-channel trafficking. We found that systemic PGB produced antinociceptive effects on CRD-evoked VMRs in naïve rats lacking pathophysiology and in MO-pretreated rats. Systemic PGB also significantly reduced Fos labelling in lumbosacral spinal cords of rats given noxious repetitive CRD; however, PGB did not alter this measure of neural activity in the brainstem. Differential brainstem processing of noxious somatic and visceral stimuli may underlie the unique lack of state-dependent actions of PGB in this visceral pain model. Single-unit recordings in the rostral ventromedial medulla (RVM) verify that brainstem processing of somatic and visceral stimuli differs. The effects of CRD on RVM cells classed as ON, OFF, or NEUTRAL were independent of their somatic responses, with surprising changes in RVM cell activity to innocuous visceral stimulation. PGB also markedly reduced the visceral responses of RVM ON-cells to noxious CRD. These results illustrate clear differences in the central processing of visceral and somatic stimuli, yet a common role for descending modulation by brainstem activity in mediating evoked pain measures.

Remifentanil-induced pronociceptive effect and its prevention with pregabalin

Background

Experimental and clinical studies have suggested that remifentanil probably causes acute tolerance or postinfusion hyperalgesia. This study was designed to confirm whether remifentanil given during propofol anesthesia induced postoperative pain sensitization, and we wanted to investigate whether pregabalin could prevent this pronociceptive effect.

Methods

Sixty patients who were scheduled for total abdominal hysterectomy were randomly allocated to receive (1) a placebo as premedication and an intraoperative saline infusion (control group), (2) a placebo as premedication and an intraoperative infusion of remifentanil at a rate of 3-4 ng/ml (remifentanil group), or (3) pregabalin 150 mg as premedication and an intraoperative infusion of remifentanil at a rate of 3-4 ng/ml (pregabalin-remifentanil group). Postoperative pain was controlled by titration of fentanyl in the postanesthetic care unit (PACU), followed by patient-controlled analgesia (PCA) with fentanyl. The patients were evaluated using the visual analogue scale (VAS) for pain scores at rest and after cough, consumption of fentanyl, sedation score and any side effects that were noted over the 48 h postoperative period.

Results

The fentanyl titration dose given in the PACU was significantly larger in the remifentanil group as compared with those of the other two groups. At rest, the VAS pain score in the remifentanil group at 2 h after arrival in the PACU was significantly higher than those in the other two groups.

Conclusions

The results of this study show that remifentanil added to propofol anesthesia causes pain sensitization in the immediate postoperative period. Pretreatment with pregabalin prevents this pronociceptive effect and so this may be useful for the management of acute postoperative pain when remifentanil and propofol are used as anesthetics.

Pregabalin as a neuroprotector after spinal cord injury in rats: biochemical analysis and effect on glial cells

As one of trials on neuroprotection after spinal cord injury, we used pregabalin. After spinal cord injury (SCI) in rats using contusion model, we observed the effect of pregabalin compared to that of the control and the methylprednisolone treated rats. We observed locomotor improvement of paralyzed hindlimb and body weight changes for clinical evaluation and caspase-3, bcl-2, and p38 MAPK expressions using western blotting. On histopathological analysis, we also evaluated reactive proliferation of glial cells. We were able to observe pregabalin's effectiveness as a neuroprotector after SCI in terms of the clinical indicators and the laboratory findings. The caspase-3 and phosphorylated p38 MAPK expressions of the pregabalin group were lower than those of the control group (statistically significant with caspase-3). Bcl-2 showed no significant difference between the control group and the treated groups. On the histopathological analysis, pregabalin treatment demonstrated less proliferation of the microglia and astrocytes. With this animal study, we were able to demonstrate reproducible results of pregabalin's neuroprotection effect. Diminished production of caspase-3 and phosphorylated p38 MAPK and as well as decreased proliferation of astrocytes were seen with the administration of pregabalin. This influence on spinal cord injury might be a possible approach for achieving neuroprotection following central nervous system trauma including spinal cord injury.

Pregabalin modulation of neurotransmitter release is mediated by change in intrinsic activation/inactivation properties of ca(v)2.1 calcium channels

In this work, we studied the effects of the anticonvulsant and analgesic drug pregabalin (PGB) on excitatory postsynaptic currents (EPSCs) at principal neurons of the mouse medial nucleus of the trapezoid body and on presynaptic calcium currents at the calyx of Held. We found that the acute application of PGB reduced the amplitude of EPSCs in a dose-dependent manner with a maximal blocking effect of approximately 30%. A clinical high-concentration dose of PGB (e.g., 500 μM) blocked Ca(v)2.1 channel-mediated currents and decreased their facilitation during a 100-Hz train, without changing their voltage-dependent activation. Furthermore, PGB also removed the inactivation of Ca(v)2.1 channels at a clinically relevant low concentration of 100 μM. These results suggest novel modulatory mechanisms mediated by the acute administration of PGB on fast excitatory synaptic transmission and might contribute to better understanding PGB anticonvulsant/analgesic clinical effects.

Pregabalin suppresses calcium-mediated proteolysis and improves stroke outcome

Pregabalin, a Ca(2+) channel α(2)δ-subunit antagonist with analgesic and antiepileptic activity, reduced neuronal loss and improved functional outcome in a mouse model of focal ischemic stroke. Pregabalin administration (5-10mg/kg, i.p.) 30-90 min after transient middle cerebral artery occlusion/reperfusion reduced infarct volume, neuronal death in the ischemic penumbra and neurological deficits at 24h post-stroke. Pregabalin significantly decreased the amount of Ca(2+)/calpain-mediated α-spectrin proteolysis in the cerebral cortex measured at 6h post-stroke. Together with the extensive clinical experience with pregabalin for other neurological indications, our findings suggest the potential for a therapeutic benefit of pregabalin in stroke patients.

Distinct gene expression profiles directed by the isoforms of the transcription factor neuron-restrictive silencer factor in human SK-N-AS neuroblastoma cells

Neuron-restrictive silencer factor (NRSF) and its isoforms are differentially regulated in rodent models of self-sustaining status epilepticus (SSSE). NRSF isoforms regulate genes associated with SSSE, including the proconvulsant tachykinins, brain-derived neurotrophic factor and multiple ion channels. NRSF isoforms may direct distinct gene expression patterns during SSSE, and the ratio of each isoform may be a causative factor in traumatic damage to the central nervous system. Here, we analysed global gene expression changes by microarray in human SK-N-AS neuroblastoma cells following the over-expression of NRSF and a truncated isoform, HZ4. We used bioinformatics software to analyse the microarray dataset and correlated these data with epilepsy candidate gene pathways. Findings were validated by reverse transcriptase-polymerase chain reaction. We demonstrated that NRSF and HZ4 direct overlapping as well as distinct gene expression patterns, and that they differentially modulated gene expression patterns associated with epilepsy. Finally, we revealed that NRSF gene expression may be modulated by the anticonvulsant, phenytoin. We have interpreted our data to reflect altered gene expression directed by NRSF that might be relevant for SSSE.

Pharmacological management of neuropathic pain in older adults: an update on peripherally and centrally acting agents

The burden of neuropathic pain in older adults is great and the practitioner is challenged to reduce symptoms and improve quality of life. Many common neuropathic pain syndromes are more prevalent in the older population, and older adults also carry greater sensitivity to certain side effects. The health care professional should have a thorough familiarity with all medications available to treat this difficult group of disorders.

Effects of pregabalin on visceral pain responses and colonic compliance in rats

BACKGROUND AND PURPOSE

Pregabalin, which binds to the alpha2-delta subunit of voltage-gated calcium channels, increased the threshold for pain during colorectal distension (CRD) in irritable bowel syndrome (IBS) patients. We tested the effects of oral pregabalin on the visceral pain-related viscerosomatic and autonomic cardiovascular responses to CRD and colonic compliance in rats.

EXPERIMENTAL APPROACH

The activity of the abdominal musculature (viscerosomatic response), monitored by electromyography and intracolonic manometry, and changes in blood pressure and heart rate, monitored by telemetry, were assessed simultaneously in conscious rats during CRD.

KEY RESULTS

Pregabalin (10-200 micromol kg(-1), p.o.) inhibited dose dependently the viscerosomatic response to phasic, noxious CRD (12 distensions at 80 mm Hg). At 200 mumol kg(-1), pregabalin also reduced the increase in blood pressure and heart rate associated with noxious CRD. Moreover, pregabalin (200 micromol kg(-1), p.o.) reduced the visceromotor response to ascending phasic CRD (10-80 mm Hg) and significantly increased the threshold pressure for response. During phasic CRD (2-20 mm Hg), pregabalin (200 micromol kg(-1), p.o.) increased intracolonic volume, resulting in a shift to the left of the pressure-volume relationship curve, indicative of an increase of compliance.

CONCLUSIONS AND IMPLICATIONS

Pregabalin reduced the viscerosomatic and autonomic responses associated with CRD-induced visceral pain and increased colonic compliance in rats. These observations confirm the analgesic activity of pregabalin on visceral pain and support the translational value of the CRD model to humans. Ligands for the alpha2-delta subunit might represent interesting compounds for the treatment of visceral pain disorders, such as IBS.

Pregabalin as a neuroprotector after spinal cord injury in rats

The over-expression of excitotoxic neurotransmitter, such as glutamate, is an important mechanism of secondary injury after spinal cord injury. The authors examined the neuroprotective effect of pregabalin (GP) which is known as to reduce glutamate secretion, in a rat model of spinal cord injury. Thirty-two male Sprague-Dawley rats were randomly allocated to four groups; the control group (contusion injury only), the methylprednisolone treated group, the minocycline treated group and the GP treated group. Spinal cord injury was produced by contusion using the New York University impactor (25 g-cm, at the 9th-10th thoracic). Functional evaluations were done using the inclined plane test and a motor rating scale. Anti-apoptotic and anti-inflammatory effects were evaluated by in situ nick-end labeling staining technique (TUNEL) and immunofluorescence staining of cord tissues obtained at 7 days post-injury. Pregabalin treated animals showed significantly better functional recovery, and anti-apoptotic and anti-inflammatory effects. Mean numbers of TUNEL positive cells in the respective groups were 63.5 +/- 7.4, 53.6 +/- 4.0, 44.2 +/- 3.9 and 36.5 +/- 3.6. Double staining (TUNEL and anti-CC1) for oligodendrocyte apoptosis, was used to calculate oligodendrocyte apoptotic indexes (AI), using the following formula AI = (No. of doubly stained cells/No. of anti-CC1 positive cells) x 100. Mean group AIs were 88.6, 46.7, 82.1 and 70.3%, respectively. Mean numbers of activated microglia (anti-OX-42 positive cells) in high power fields were 29.8 +/- 3.9, 22.7 +/- 4.1, 21.0 +/- 3.9 and 17.8 +/- 4.3, respectively. This experiment demonstrates that GP can act as a neuroprotector after SCI in rats, and its anti-apoptotic and anti-inflammatory effects are related to its neuroprotective effect. Further studies are needed to unveil the specific mechanism involved at the receptor level.

The calcium channel alpha2/delta1 subunit is involved in extracellular signalling

The alpha2/delta1 subunit forms part of the dihydropyridine receptor, an essential protein complex for excitation-contraction (EC) coupling in skeletal muscle. Because of the lack of a viable knock-out animal, little is known regarding the role of the alpha2/delta1 subunit in EC coupling or in other cell functions. Interestingly, the alpha2/delta1 appears before the alpha1 subunit in development and contains extracellular conserved domains known to be important in cell signalling and inter-protein interactions. These facts raise the possibility that the alpha2/delta1 subunit performs vital functions not associated with EC coupling. Here, we tested the hypothesis that the alpha2/delta1 subunit is important for interactions of muscle cells with their environment. Using confocal microscopy, we followed the immunolocalization of alpha2/delta1 and alpha1 subunits with age. We found that in 2-day-old myotubes, the alpha2/delta1 subunit concentrated towards the ends of the cells, while the alpha1 subunit clustered near the centre. As myotubes aged (6-12 days), the alpha2/delta1 became evenly distributed along the myotubes and co-localized with alpha1. When the expression of alpha2/delta1 was blocked with siRNA, migration, attachment and spreading of myoblasts were impaired while the L-type calcium current remained unaffected. The results suggest a previously unidentified role of the alpha2/delta1 subunit in skeletal muscle and support the involvement of this protein in extracellular signalling. This new role of the alpha2/delta1 subunit may be crucial for muscle development, muscle repair and at times in which myoblast attachment and migration are fundamental.

Redundancy of Cav2.1 channel accessory subunits in transmitter release at the mouse neuromuscular junction

Ca(v)2.1 (P/Q-type) channels possess a voltage-sensitive pore-forming alpha(1) subunit that can associate with the accessory subunits alpha(2)delta, beta and gamma. The primary role of Ca(v)2.1 channels is to mediate transmitter release from nerve terminals both in the central and peripheral nervous system. Whole-cell voltage-clamp studies in in vitro expression systems have indicated that accessory channel subunits can have diverse modulatory effects on membrane expression and biophysical properties of Ca(v)2.1 channels. However, there is only limited knowledge on whether similar modulation also occurs in the specific presynaptic environment in vivo and, hence, whether accessory subunits influence neurotransmitter release. Ducky, lethargic and stargazer are mutant mice that lack functional alpha(2)delta-2, beta(4) and gamma(2) accessory Ca(v) channel subunits, respectively. The neuromuscular junction (NMJ) is a peripheral synapse, where transmitter release is governed exclusively by Ca(v)2.1 channels, and which can be characterized electrophysiologically with relative experimental ease. In order to investigate a possible synaptic influence of accessory subunits in detail, we electrophysiologically measured acetylcholine (ACh) release at NMJs of these three mutants. Surprisingly, we did not find any changes compared to wild-type littermates, other than a small reduction (25%) of evoked ACh release at ducky NMJs. This effect is most likely due to the approximately 40% reduced synapse size, associated with the reduced size of ducky mice, rather than resulting directly from reduced Ca(v)2.1 channel function due to alpha(2)delta-2 absence. We conclude that alpha(2)delta-2, beta(4), and gamma(2) accessory subunits are redundant for the transmitter release-mediating function of presynaptic Ca(v)2.1 channels at the mouse NMJ.

Pharmacology and mechanism of action of pregabalin: the calcium channel alpha2-delta (alpha2-delta) subunit as a target for antiepileptic drug discovery

Pregabalin (Lyrica) is a new antiepileptic drug that is active in animal seizure models. Pregabalin is approved in US and Europe for adjunctive therapy of partial seizures in adults, and also has been approved for the treatment of pain from diabetic neuropathy or post-herpetic neuralgia in adults. Recently, it has been approved for treatment of anxiety disorders in Europe. Pregabalin is structurally related to the antiepileptic drug gabapentin and the site of action of both drugs is similar, the alpha2-delta (alpha2-delta) protein, an auxiliary subunit of voltage-gated calcium channels. Pregabalin subtly reduces the synaptic release of several neurotransmitters, apparently by binding to alpha2-delta subunits, and possibly accounting for its actions in vivo to reduce neuronal excitability and seizures. Several studies indicate that the pharmacology of pregabalin requires binding to alpha2-delta subunits, including structure-activity analyses of compounds binding to alpha2-delta subunits and pharmacology in mice deficient in binding at the alpha2-delta Type 1 protein. The preclinical findings to date are consistent with a mechanism that may entail reduction of abnormal neuronal excitability through reduced neurotransmitter release. This review addresses the preclinical pharmacology of pregabalin, and also the biology of the high affinity binding site, and presumed site of action.