Riluzole restores motor activity in rats with post-traumatic peripheral neuropathy

Riluzole, a neuroprotective agent, preserves erectile function following bilateral cavernous nerve injury in male rats

Neurogenic erectile dysfunction is a highly prevalent complication in men undergoing radical prostatectomy. The underlying mechanisms remain incompletely defined and the effective therapy has been limited. This study aimed to evaluate the protective effect of riluzole and the role of PKC β and excitatory amino acid transporters (EAATs) mediating this effect in a rat model of bilateral cavernous injury (BCNI). A total of 48 male Sprague-Dawley rats were divided into sham, BCNI (at 7, 15 days post-injury) and BCNI treated with riluzole (8 mg/kg/day) groups. Erectile function was measured as maximum intracavernosal pressure (mICP)/mean arterial pressure (MAP) and total ICP/MAP. Changes in protein expressions of phospho (p)-PKC β IIser660 and EAATs were analysed in penis and major pelvic ganglion with western blotting. BCNI decreased erectile function at 7 and 15 days post-injury (mICP/MAP at 4 V: 0.45 ± 0.06 vs 0.84 ± 0.07; 0.34 ± 0.04 vs 0.77 ± 0.04 respectively; p < 0.001) whereas riluzole treatment (for 15 days) preserved erectile function (mICP/MAP at 4 V: 0.62 ± 0.03 vs 0.34 ± 0.04; p < 0.01). The decline in the expression of p-PKC β IIser660 was observed in penis at 7 and 15 days post-injury (p = 0.0003, p = 0.0033), which was prevented by riluzole treatment for 15 days (p = 0.0464). While expressions of EAAT-1 and EAAT-2 decreased in major pelvic ganglion following BCNI (p = 0.0428, p = 0.002), riluzole treatment for 15 days prevented the decrease only in EAAT-2 expression (p = 0.0456). Riluzole improved erectile function via possibly interacting with PKC β II and glutamatergic pathways, as a potential therapeutic candidate for erectile dysfunction.

Recent Findings on the Effects of Pharmacological Agents on the Nerve Regeneration after Peripheral Nerve Injury

Peripheral nerve injuries (PNIs) are accompanied with neuropathic pain and functional disability. Despite improvements in surgical repair techniques in recent years, the functional recovery is yet unsatisfied. Indeed a successful nerve repair depends not only on the surgical strategy but also on the cellular and molecular mechanisms involved in traumatic nerve injury. In contrast to all strategies suggested for nerve repair, pharmacotherapy is a cheap, accessible and non-invasive treatment that can be used immediately after nerve injury. This study aimed to review the effects of some pharmacological agents on the nerve regeneration after traumatic PNI evaluated by functional, histological and electrophysiological assessments. In addition, some cellular and molecular mechanisms responsible for their therapeutic actions, restricted to neural tissue, are suggested. These findings can not only help to find better strategies for peripheral nerve repair, but also to identify the neuropathic effects of various medications and their mechanisms of action.

Peripheral nerve and diclofenac sodium: Molecular and clinical approaches

Nonsteroidal anti-inflammatory drugs (NSAIDs) are the most frequently prescribed medications worldwide. Diclofenac sodium (DS), one of these NSAIDs, has a high specificity for arachidonic acid-degrading cyclooxygenase (COX)-2 enzymes. This drug can be used to relieve neuropathic pain. In this review, we examine the relevant researches, including in vivo, animal, and clinical human studies, with the aim of understanding the effect of DS on the peripheral nerves. In injured nerves, COX-2 is potently upregulated around the injury site. When a nerve is damaged, both COX-1 and COX-2 expression is increased in macrophages and Schwann cells. In addition, COX inhibitors can promote axonal outgrowth in cultured neurons. Neuropathic pain occurs after injury and leads to dysfunction of the peripheral nervous system. NSAIDs can modulate the nociceptive and inflammatory pain pathways and control neuropathic pain. DS may accelerate nerve regeneration and its effects on healing, as well as causing deleterious effects in the developing nerves. DS teratogenicity disrupts myelin sheath thickness and axon structure. Understanding the possible benefits and limitations of DS and specific conditions such as prenatal use will be of benefit in clinical practice.

The effect of Riluzole on functional recovery of locomotion in the rat sciatic nerve crush model

PURPOSE

Peripheral nerve injury (PNI) is common disorder that represents more than 3 % of all traumatic injury cases. One type of PNI, sciatic nerve injury, leads to considerable motoneuron dysfunction. Because Riluzole is clinically approved for the treatment of motoneuron disease, we evaluated whether Riluzole treatment could enhance the nerve regeneration process and improve functional outcome after sciatic nerve crush in rats.

METHODS

In acute treatment groups, a single dose of Riluzole (6 and 8 mg/kg) was administered intra-peritoneally 15 min after the crush nerve injury. In the chronic treatment groups, animals were treated with Riluzole (4 and 6 mg/kg/d) for 8 days. Sciatic functional index (SFI) was evaluated for 9 weeks after injury. Furthermore, electrophysiological and morphometric evaluations were performed at the 9th week following injury.

RESULTS

Acute and chronic administrations of Riluzole immediately after sciatic nerve crush result in significantly delayed regeneration and reduced motor function outcome.

CONCLUSIONS

These findings suggest that early administration of even a single dose of Riluzole after sciatic nerve crush injury can delay motor function recovery. This effect may not depend on its anti-nociceptive activity.

Short-term effect of acute and repeated urinary bladder inflammation on thigmotactic behaviour in the laboratory rat

Understanding the non-sensory components of the pain experience is crucial to developing effective treatments for pain conditions. Chronic pain is associated with increased incidence of anxio-depressive disorders, and patients often report feelings of vulnerability which can decrease quality of life. In animal models of pain, observation of behaviours such as thigmotaxis can be used to detect such affective disturbances by exploiting the influence of nociceptive stimuli on the innate behavioural conflict between exploration of a novel space and predator avoidance behaviour. This study investigates whether acute and repeated bladder inflammation in adult female Wistar rats increases thigmotactic behaviour in the open field paradigm, and aims to determine whether this correlates with activation in the central amygdala, as measured by c-Fos immunoreactivity. Additionally, up-regulation of inflammatory mediators in the urinary bladder was measured using RT-qPCR array featuring 92 transcripts to examine how local mediators change under experimental conditions. We found acute but not repeated turpentine inflammation of the bladder increased thigmotactic behaviour (decreased frequency of entry to the inner zone) in the open field paradigm, a result that was also observed in the catheter-only instrumentation group. Decreases in locomotor activity were also observed in both models in turpentine and instrumentation groups. No differences were observed in c-Fos activation, although a general increased in activation along the rostro-caudal axis was seen. Inflammatory mediator up-regulation was greatest following acute inflammation, with CCL12, CCL7, and IL-1β significantly up-regulated in both conditions when compared to naïve tissue. These results suggest that acute catheterisation, with or without turpentine inflammation, induces affective alterations detectable in the open field paradigm accompanied by up-regulation of multiple inflammatory mediators.

Riluzole- and Resveratrol-Induced Delay of Retinal Ganglion Cell Death in an Experimental Model of Glaucoma

PURPOSE

To evaluate the effects of the neuroprotective agents riluzole and resveratrol on the survival of retinal ganglion cells (RGCs) when administered alone or in combination.

MATERIALS AND METHODS

Experimental glaucoma was induced by injecting hyaluronic acid into the anterior chamber of Wistar albino rats weekly for a six-week period. Intraocular pressure was measured before and immediately after glaucoma induction. The neuroprotective effects of daily intraperitoneal injections of riluzole (8 mg/kg) and resveratrol (10 mg/kg) were evaluated and compared. After the six-week period, dextran tetramethylrhodamine was applied into the optic nerve and the density of surviving RGCs was evaluated by counting the labeled RGCs in whole mount retinas for retrograde labeling of RGCs.

RESULTS

The mean numbers of RGCs were significantly preserved in all treatment groups compared to the vehicle-treated glaucoma group (G). The mean number of RGCs in mm(2) were 1207 ± 56 in the control group (C), 404 ± 65 in G group, 965 ± 56 in riluzole-treated group in the early phase of glaucoma (E-Ri), 714 ± 25 in riluzole-treated group in the late phase of glaucoma (L-Ri), 735 ± 29 in resveratrol-treated group in the early phase of glaucoma (E-Re), 667 ± 20 in resveratrol-treated group in the late phase of glaucoma (L-Re), and 1071 ± 49 in riluzole and resveratrol combined-treated group in the early phase of glaucoma (E-RiRe group).

CONCLUSIONS

When used either alone or in combination, both riluzole and resveratrol, two agents with different mechanisms of action in glaucoma, significantly delayed RGC loss in this study's experimental glaucoma model.

Riluzole in psychiatry: a systematic review of the literature

BACKGROUND

The glutamate system seems to be an important contributor to the pathophysiology of mood and anxiety disorders. Thus, glutamatergic modulators are reasonable candidate drugs to test in patients with mood and anxiety disorders. Riluzole, a neuroprotective agent with anticonvulsant properties approved for the treatment of amyotrophic lateral sclerosis (ALS) is one such agent.

OBJECTIVE

To assess the potential risks and benefits of riluzole treatment in psychiatric patients.

METHODS

A PubMed search was performed using the keywords 'riluzole', 'inhibitor of glutamate release' and 'glutamatergic modulator' to identify all clinical studies and case reports involving riluzole in psychiatric patients.

RESULTS/CONCLUSION

Riluzole's side effect profile is favorable and preliminary results regarding riluzole for the treatment of severe mood, anxiety and impulsive disorders are encouraging.

Riluzole promotes cell survival and neurite outgrowth in rat sensory neurones in vitro

This study explored the effects of riluzole administration on cell survival and neurite growth in adult and neonatal rat dorsal root ganglion (DRG) neurones in vitro. Neuronal survival was assessed by comparing numbers of remaining neurones in vehicle- and riluzole-treated cultures. A single dose of 0.1 microm riluzole was sufficient to promote neuronal survival in neonatal DRG cultures, whereas repeated riluzole administration was necessary in adult cultures. However, a single administration of riluzole was sufficient to induce neuritogenesis, promote neurite branching and enhance neurite outgrowth in both neonatal and adult DRG cultures. The effects of a single dose of riluzole on adult DRG neurones after peripheral nerve or dorsal root injury were also studied in vitro at 48 h. For both types of injury, riluzole enhanced neurite outgrowth in terms of number, length and branch pattern significantly more on the injured side as compared with the contralateral side. No effect was seen on cell survival. The results suggest that, in addition to its cell survival effects, riluzole has novel growth-promoting effects on sensory neurones in vitro and that riluzole may offer a new way to promote sensory afferent regeneration following peripheral injury.

An important functional role of persistent Na+ current in carotid body hypoxia transduction

Systemic hypoxia in mammals is sensed and transduced by the carotid body into increased action potential (AP) frequency on the sinus nerve, resulting in increased ventilation. The mechanism of hypoxia transduction is not resolved, but previous work suggested that fast Na(+) channels play an important role in determining the rate and timing of APs (Donnelly, DF, Panisello JM, and Boggs D. J Physiol. 511: 301-311, 1998). We speculated that Na(+) channel activity between APs, termed persistent Na(+) current (I(NaP)), is responsible for AP generation that and riluzole and phenytoin, which inhibit this current, would impair organ function. Using whole cell patch clamp recording of intact petrosal neurons with projections to the carotid body, we demonstrated that I(NaP) is present in chemoreceptor afferent neurons and is inhibited by riluzole. Furthermore, discharge frequencies of single-unit, chemoreceptor activity, in vitro, during normoxia (Po(2) 150 Torr) and during acute hypoxia (Po(2) 90 Torr) were significantly reduced by riluzole concentrations at or above 5 microM, and by phenytoin at 100 microM, without significant affect on nerve conduction time, AP magnitude (inferred from extracellular field), and AP duration. The effect of both drugs appeared solely postsynaptic because hypoxia-induced catecholamine release in the carotid body was not altered by either drug. The respiratory response of unanesthetized, unrestrained 2-wk-old rats to acute hypoxia (12% inspired O(2) fraction), which was measured with whole body plethysmography, was significantly reduced after treatment with riluzole (2 mg/kg ip) and phenytoin (20 mg/kg ip). We conclude that I(NaP) is present in chemoreceptor afferent neurons and serves an important role in peripheral chemoreceptor function and, hence, in the ventilatory response to hypoxia.