Neuroprotective effects of gabapentin on spinal cord ischemia-reperfusion injury in rabbits

Behavioral and physiologic effects of a single dose of oral gabapentin in rabbits (Oryctolagus cuniculus)

Stress in rabbits (Oryctolagus cuniculus) may influence veterinarians' ability to assess their health and can lead to complications such as gastrointestinal hypomotility and poor anesthetic outcomes. Gabapentin has been used as an anxiolytic in various species, but little information is available on its use in rabbits. To assess the effect of gabapentin on stress in rabbits, 5 female and 3 male New Zealand white rabbits, aged 8-12 months, weighing 3-4.5 kg, were administered a single dose (25 mg/kg) of oral compounded gabapentin. Effects on individual behaviors and selected physiologic parameters were assessed by a blinded observer using a human intruder test and tractability score (summed total 0-8, most to least tractable). Heart and respiratory rate, rectal temperature, body weight, and fecal output were also recorded. Baseline measurements for each rabbit were assessed immediately prior to gabapentin administration, and at 1, 2, and 4 hours post-administration. With this method rabbits acted as their own concurrent control group. Rabbits were assessed at 7 AM, 11 AM, and 3 PM. Data were analyzed as continuous, binary, and continuous nonparametric (P ≤ .05). No significant differences in physiologic parameters were observed between baseline and the post-administration timepoints. Fecal output was reduced similar to baseline measurements. Behaviors pressing down decreased (at 2 and 4 hours; P = .05 and P = .013, respectively) and approaching human increased (at 2 hours; P = .022) post-gabapentin compared to baseline. Tractability scores were improved at the 2-hour timepoint compared to baseline (Friedman P = .0461; Wilcoxon P = .0413). These results suggest gabapentin 25 mg/kg orally decreased reactivity with a peak effect at 2 hours, without significant effects on measured physiologic parameters. Oral gabapentin in rabbits should be considered to reduce stress in the presence of humans and to facilitate handling.

Treatment of Pain in Rabbits

Rabbits occupy facets of veterinary medicine spanning from companion mammals, wildlife medicine, zoologic species, and research models. Therefore, analgesia is required for a variety of conditions in rabbits and is a critical component of patient care. Considerations when selecting an analgesic protocol in rabbits include timing of administration, route of administration, degree or anticipated pain, ability to access or use controlled drugs, systemic health, and any potential side effects. This review focuses on pharmacologic and locoregional management of pain in rabbits and emphasizes the need for further studies on pain management in this species.

Harnessing cortical plasticity via gabapentinoid administration promotes recovery after stroke

Stroke causes devastating sensory-motor deficits and long-term disability due to disruption of descending motor pathways. Restoration of these functions enables independent living and therefore represents a high priority for those afflicted by stroke. Here, we report that daily administration of gabapentin, a clinically approved drug already used to treat various neurological disorders, promotes structural and functional plasticity of the corticospinal pathway after photothrombotic cortical stroke in adult mice. We found that gabapentin administration had no effects on vascular occlusion, haemodynamic changes nor survival of corticospinal neurons within the ipsilateral sensory-motor cortex in the acute stages of stroke. Instead, using a combination of tract tracing, electrical stimulation and functional connectivity mapping, we demonstrated that corticospinal axons originating from the contralateral side of the brain in mice administered gabapentin extend numerous collaterals, form new synaptic contacts and better integrate within spinal circuits that control forelimb muscles. Not only does gabapentin daily administration promote neuroplasticity, but it also dampens maladaptive plasticity by reducing the excitability of spinal motor circuitry. In turn, mice administered gabapentin starting 1 h or 1 day after stroke recovered skilled upper extremity function. Functional recovery persists even after stopping the treatment at 6 weeks following a stroke. Finally, chemogenetic silencing of cortical projections originating from the contralateral side of the brain transiently abrogated recovery in mice administered gabapentin, further supporting the conclusion that gabapentin-dependent reorganization of spared cortical pathways drives functional recovery after stroke. These observations highlight the strong potential for repurposing gabapentinoids as a promising treatment strategy for stroke repair.

Beneficial "Pharmaceutical Pleiotropy" of Gabapentinoids in Spinal Cord Injury: A Case for Refining Standard-of-Care

Spinal cord injury results in devastating neurological deficits accompanied by lifelong disability and significant economic burden. While the development of novel compounds or cell-based interventions for spinal cord injury is unquestionably worthwhile, a complementary approach examines current standards of care and the degree to which these can be optimized to benefit long-term neurological function. Numerous classes of drugs, already in use in the acute phase of spinal cord injury, are intriguing because they (1) readily cross the blood-spinal cord barrier to modulate activity in the central nervous system and (2) are administered during a window of time in which neuroprotection, and even some repair, are feasible. Here, we review a rare case of convergent lines of evidence from both preclinical and human studies to support the early administration of a class of drug (ie, gabapentinoids) to both foster motor recovery and reduce the severity of neuropathic pain.

Pharmacokinetic Profiles of Gabapentin after Oral and Subcutaneous Administration in Black-tailed Prairie Dogs (Cynomys ludovicianus)

In veterinary and human medicine, gabapentin (a chemical analog of γ-aminobutyric acid) is commonly prescribed to treat postoperative and chronic neuropathic pain. This study explored the pharmacokinetics of oral and subcutaneous administration of gabapentin at high (80 mg/kg) and low (30 mg/kg) doses as a potential analgesic in black-tailed prairie dogs (Cynomys ludovicianus; n = 24). The doses (30 and 80 mg/kg) and half maximal effective concentration (1.4 to 16.7 ng/mL) for this study were extrapolated from pharmacokinetic efficacy studies in rats, rabbits, and cats. Gabapentin in plasma was measured by using an immunoassay, and data were evaluated using noncompartmental analysis. The peak plasma concentrations (mean ±1 SD) were 42.6 ±14.8 and 115.5 ±15.2 ng/mL, respectively, after 30 and 80 mg/kg SC and 14.5 ±3.5 and 20.7 ±6.1 ng/mL after the low and high oral dosages, respectively. All peak plasma concentrations of gabapentin occurred within 5 h of administration. Disappearance half-lives for the low and high oral doses were 7.4 ± 6.0 h and 5.0 ± 0.8 h, respectively. The results of this study demonstrate that oral administration of gabapentin at low (30 mg/kg) doses likely would achieve and maintain plasma concentrations at half maximum effective concentration for 12 h, making it a viable option for an every 12-h treatment.

Investigation of the Effect of Alemtuzumab in an Experimental Spinal Cord Trauma Model in Rats

OBJECTIVE

Spinal cord injuries generate the most negative response to medical treatment among all general body injuries. This important morbidity is thought to be caused by a complex secondary damage mechanism. In the present study, we examined the neuroprotective effects of alemtuzumab in a spinal cord trauma model.

METHODS

We divided 24 Long-Evans male rats into 4 groups (n = 6 per group). Laminectomy was performed at T5-T8 in all groups. Trauma was applied using the Yasargil temporary aneurysm clip for 60 seconds at these spinal cord levels in all groups, except for group 1. Next, 1 mg/kg of alemtuzumab was administered to each rat in groups 3 and 4. A functional evaluation was performed on days 1, 3, and 5 in groups 1, 2, and 4, and the rats were then sacrificed. The rats in group 3 were sacrificed on the third postoperative day to observe the early effects of alemtuzumab. The biochemical examination findings of malondialdehyde and glutathione in plasma and tissue samples and histopathological findings of the spinal cord were evaluated and compared by statistical analysis.

RESULTS

The inflammatory findings in the trauma group were not seen in either group treated with alemtuzumab. The clinical motor examination and inclined plane test results were also significantly better in these groups.

CONCLUSION

Our results have shown that alemtuzumab might prevent spinal cord injury after trauma and is a histopathologically and biochemically strong anti-inflammatory, antioxidant, and neuroprotective agent.

Neuroprotective Effects of Vigabatrin on Spinal Cord Ischemia-Reperfusion Injury

OBJECTIVE

Spinal cord ischemia is a serious and catastrophic clinicopathologic condition. Despite studies reported over the last 20 years, alternative and efficient treatment options remain unclear. We examined the neuroprotective effects of vigabatrin on a spinal ischemia-reperfusion model.

METHODS

We divided 24 New Zealand rabbits into 4 groups (control, ischemia reperfusion, and low-dose and high-dose vigabatrin). The control group underwent only abdominal surgery, whereas an abdominal aortic cross-clamp model of spinal ischemia was performed in the other groups. Clips were removed after 30 minutes and 50 and 150 mg/kg vigabatrin was administered intraperitoneally to the low-dose and high-dose groups, respectively. Neurologic examination was performed for 48 hours, after which the rabbits were sacrificed and a blood sample obtained. Biochemical examination of malondialdehyde, advanced oxidation protein products, total nitric oxide, and glutathione levels and superoxide dismutase activities in plasma and tissue sample, and histopathologic examination of the spinal cord were performed and statistical results compared between the groups.

RESULTS

Low-dose vigabatrin had statistically significant effects of neuroprotection on spinal ischemia. Although high-dose vigabatrin had similar effects, the results were not statistically significant for all parameters of biochemical analysis. In addition, histopathologic examination showed some toxic effects of high-dose vigabatrin.

CONCLUSIONS

Neuroprotective effects of vigabatrin are shown. For clinical use, further studies are needed.

Protection from spinal cord ischemia-reperfusion damage with alpha-lipoic acid preconditioning in an animal model

Background

This study aims to investigate whether preconditioning with alpha-lipoic acid has any protective effect in neuronal damage in an experimental spinal cord ischemia-reperfusion injury model.

Methods

Eighteen adult male New Zealand rabbits (2.4-3.5 kg) were equally divided into sham, control and treatment groups. The abdominal aorta was occluded for 30 min proximally 1 cm below the renal artery and distally 1 cm above the bifurcation using aneurysm clips in control and treatment groups. Treatment group received intraperitoneal 100 mg/kg lipoic acid 20 min before aortic cross-clamping. The animals were sacrificed 48 hours after the operation and spinal cord segments between L2 and L5 were removed for biochemical and histopathological analysis. Levels of glutathione, malondialdehyde, total nitrate/nitrite, advanced oxidation protein products, catalase, superoxide dismutase, and glutathione peroxidase were examined in spinal cord.

Results

Preconditioning with alpha-lipoic acid demonstrated significantly favorable effects in all measured parameters of oxidative stress. Histopathological evaluation of the tissues also demonstrated significantly decreased neuronal degeneration, axonal damage, and microglial and astrocytic infiltration in the treatment group compared to the control group.

Conclusion

The results of this study indicate that alpha-lipoic acid administration before aortic cross-clamping has significant neuroprotective effect on spinal cord injury in rabbits.

Early Administration of Gabapentinoids Improves Motor Recovery after Human Spinal Cord Injury

The anticonvulsant pregabalin promotes neural regeneration in a mouse model of spinal cord injury (SCI). We have also previously observed that anticonvulsants improve motor outcomes following human SCI. The present study examined the optimal timing and type of anticonvulsants administered in a large, prospective, multi-center, cohort study in acute SCI. Mixed-effects regression techniques were used to model total motor scores at 1, 3, 6, and 12 months post injury. We found that early (not late) administration of anticonvulsants significantly improved motor recovery (6.25 points over 1 year). The beneficial effect of anticonvulsants remained significant after adjustment for differences in 1-month motor scores and injury characteristics. A review of a subset of patients revealed that gabapentinoids were the most frequently administrated anticonvulsant. Together with preclinical findings, intervention with anticonvulsants represents a potential pharmacological strategy to improve motor function after SCI.

α2δ-1 Signaling Drives Cell Death, Synaptogenesis, Circuit Reorganization, and Gabapentin-Mediated Neuroprotection in a Model of Insult-Induced Cortical Malformation

Developmental cortical malformations (DCMs) result from pre- and perinatal insults, as well as genetic mutations. Hypoxia, viral infection, and traumatic injury are the most common environmental causes of DCMs, and are associated with the subsyndromes focal polymicrogyria and focal cortical dysplasia (FCD) Type IIId, both of which have a high incidence of epilepsy. Understanding the molecular signals that lead to the formation of a hyperexcitable network in DCMs is critical to devising novel treatment strategies. In a previous study using the freeze-lesion (FL) murine model of DCM, we found that levels of thrombospondin (TSP) and the calcium channel auxiliary subunit α2δ-1 were elevated. TSP binds to α2δ-1 to drive the formation of excitatory synapses during development, suggesting that overactivation of this pathway may lead to exuberant excitatory synaptogenesis and network hyperexcitability seen in DCMs. In that study, antagonizing TSP/α2δ-1 signaling using the drug gabapentin (GBP) reduced many FL-induced pathologies. Here, we used mice with a genetic deletion of α2δ-1 to determine how α2δ-1 contributes to cell death, elevated excitatory synapse number, and in vitro network function after FL and to examine the molecular specificity of GBP's effects. We identified a critical role for α2δ-1 in FL-induced pathologies and in mediating the neuroprotective effects of GBP. Interestingly, genetic deletion of α2δ-1 did not eliminate GBP's effects on synaptogenesis, suggesting that GBP can have α2δ-1-independent effects. Taken together these studies suggests that inhibiting α2δ-1 signaling may have therapeutic promise to reduce cell death and network reorganization associated with insult-induced DCMs.

Effects of Pain and Pain Management on Motor Recovery of Spinal Cord–Injured Patients

Background. Approximately 60% of patients suffering from acute spinal cord injury (SCI) develop pain within days to weeks after injury, which ultimately persists into chronic stages. To date, the consequences of pain after SCI have been largely examined in terms of interfering with quality of life. Objective. The objective of this study was to examine the effects of pain and pain management on neurological recovery after SCI. Methods. We analyzed clinical data in a prospective multicenter observational cohort study in patients with SCI. Using mixed effects regression techniques, total motor and sensory scores were modelled at 1, 3, 6, and 12 months postinjury. Results. A total of 225 individuals were included in the study (mean age: 45.8 ± 18 years, 80% male). At 1 month postinjury, 28% of individuals with SCI reported at- or below-level neuropathic pain. While pain classification showed no effect on neurological outcomes, individuals administered anticonvulsant medications at 1 month postinjury showed significant reductions in pain intensity (2 points over 1 year; P < .05) and greater recovery in total motor scores (7.3 points over 1 year; P < .05). This drug effect on motor recovery remained significant after adjustment for injury level and injury severity, pain classification, and pain intensity. Conclusion. While initial pain classification and intensity did not reveal an effect on motor recovery following acute SCI, anticonvulsants conferred a significant beneficial effect on motor outcomes. Early intervention with anticonvulsants may have effects beyond pain management and warrant further studies to evaluate the therapeutic effectiveness in human SCI.

Efficacy of Anti-Epileptic Drugs in the Treatment of Tumor and Its Associated Epilepsy: An in vitro Perspective

The change in the therapeutic targets from neuron to glia has proved beneficial in the treatment of many psychiatric disorders. The anti-epileptic drugs (AEDs) have been widely prescribed for the treatment of partial and complete seizures, bipolar disorder among others. The current study was carried out to explore the efficacy of some conventional and novel AEDs for the treatment of tumor-associated epilepsy which develops in 29-49% of the patients diagnosed with brain tumors. We used C6 glioma cell line as model system to study the effect of selected AEDs, viz., gabapentin (GBP), valproic acid (VPA) and topiramate (TPM). Morphometry, cell cycle analysis, apoptosis, expression of different protein markers, viz., GFAP, HSP70 and nuclear factor-κB (NFκB) were studied in AED-treated cultures. The study was further extended to rat hypothalamic primary explant cultures, and cell migration and expression of plasticity markers - neural cell adhesion molecule (NCAM) and polysialylation of NCAM (PSA-NCAM) - were studied in the explants. TPM was observed to show more pronounced increase in apoptosis of glioblastoma cells accompanied by significant downregulation in the expression of HSP70 and NFκB. TPM-treated explants also showed highest process ramification and cellular migration accompanied by intense expression of the plasticity markers as compared to those treated with GBP and VPA. Among the 3 AEDs tested, TPM was observed to show more promising effects on cytoprotection and plasticity of C6 glioma cells.

Does the intrathecal propofol have a neuroprotective effect on spinal cord ischemia?

The neuroprotective effects of propofol have been confirmed. However, it remains unclear whether intrathecal administration of propofol exhibits neuroprotective effects on spinal cord ischemia. At 1 hour prior to spinal cord ischemia, propofol (100 and 300 µg) was intrathecally administered in rats with spinal cord ischemia. Propofol pre-treatment greatly improved rat pathological changes and neurological function deficits at 24 hours after spinal cord ischemia. These results suggest that intrathecal administration of propofol exhibits neuroprotective effects on spinal cord structural and functional damage caused by ischemia.

Methodology of motor evoked potentials in a rabbit model

Spinal cord ischemia (SCI) is a devastating complication of aortic operations. Neuromonitoring using motor evoked potentials (MEPs) is a sensitive modality to detect SCI in humans. We describe a leporine SCI model using MEPs to test pharmaceutical therapeutics and other neuroprotective adjuncts. In 80 rabbits, methods to obtain MEPs in normotensive and ischemic rabbits were developed. The effects of isoflurane, propofol, apnea, and hypotension on lower extremity MEPs were studied. Lower extremity MEPs disappear upon SCI induction in 78 of 78 (100 %) rabbits. Prior to SCI induction and during apneic episodes, lower extremity MEPs were lost in all (100 %) and upper extremity MEPs in one (25 %). Isoflurane was used in four experiments, with loss of lower extremity MEPs in all four (100 %) and loss of upper extremity MEPs in zero. With propofol upper extremity, MEPs were obtainable in 80 of 80 rabbits (100 %) and lower extremity MEPs in 78 of 80 rabbits (97.5 %) prior to SCI induction. The presence of these lower extremity MEPs prior to SCI induction was not correlated with systolic or diastolic blood pressure. Disappearance of MEPs occurred in all 45 rabbits with postoperative lower extremity impairment. MEPs in the leporine model correlate closely with paraplegia. MEPs are influenced by inhaled anesthetics and apnea but not by hypotension alone. Propofol anesthesia provides reliable MEPs. This study provides the basis for a reproducible model of SCI to be used for novel therapeutic drug development.

Preventive effect of intrathecal paracetamol on spinal cord injury in rats

Background:

Ischemic injury of the spinal cord during the surgical repair of thoracoabdominal aortic aneurysms might lead to paraplegia. Although a number of different mechanisms have been proposed, the exact cause of paraplegia has remained unknown, hampering the development of effective pharmacologic or other strategies for prevention of this condition. A number of studies suggested that cyclooxygenases (COX) contribute to neural breakdown; thus, COX inhibitors might reduce injury.

Objectives:

We aimed to assess the preventive effect of intrathecal (IT) pretreatment with paracetamol on spinal cord injury in a rat model.

Materials and Methods:

This experimental study was performed in Ataturk University Animal Research Laboratory Center, Erzurum, Turkey. Adult male Wistar rats were randomly allocated to three experimental groups (n = 6) to receive IT physiologic saline (controls), 50 µg of paracetamol, or 100 µg paracetamol one hour before induction of spinal cord ischemia. Six other rats were considered as the sham group. For the assessment of ischemic injury, motor functions of the hind limbs and histopathologic changes of the lumbar spinal cord were evaluated. Additional 20 rats were divided into two equal groups for the second part of the study where the survival rates were recorded in controls and in animals receiving 100 µg of paracetamol during the 28-day observation period.

Results:

Pretreatment with 100 µg of paracetamol resulted in a significant improvement in motor functions and histopathologic findings (P < 0.05). Despite a higher rate of survival in 100 µg of paracetamol group (70%) at day 28, the difference was not statistically significant in comparison with controls.

Conclusions:

Our results suggest a protective effect of pretreatment with IT paracetamol on ischemic spinal cord injury during thoracolumbar aortic aneurysm surgery.

Effects of curcumin on acute spinal cord ischemia-reperfusion injury in rabbits

Object

The object of this study was to conduct a prospective, randomized, laboratory investigation of the neuroprotective effects of curcumin functionally, biochemically, and histologically in an experimental acute spinal cord ischemia-reperfusion injury on rabbits.

Methods

Eighteen rabbits were randomly assigned to 1 of 3 groups: the sham group, the ischemia-reperfusion group, or the curcumin group. Spinal cord ischemia was induced by applying an infrarenal aortic cross-clamp for 30 minutes. At 48 hours after ischemia, neurological function was evaluated with modified Tarlov criteria. Biochemical changes in the spinal cord and plasma were observed by measuring levels of malondialdehyde (MDA), advanced oxidation protein products (AOPP), glutathione (GSH), superoxide dismutase (SOD), catalase (CAT), nitrite/nitrate, and tumor necrosis factor-α (TNF-α). Histological changes were examined with H & E staining. Immunohistochemical staining with antibodies against caspase-3 was performed to evaluate cell apoptosis after ischemia.

Results

In the curcumin group, neurological outcome scores were statistically significantly better compared with the ischemia-reperfusion group. In the ischemia-reperfusion group, MDA, AOPP, and nitrite/nitrate levels were significantly elevated in the spinal cord tissue and the plasma by the induction of ischemia-reperfusion. The curcumin treatment significantly prevented the ischemia-reperfusion–induced elevation of nitrite/nitrate and TNF-α. In addition, the spinal cord tissue and the plasma SOD, GSH, and CAT levels were found to be preserved in the curcumin group and not statistically different from those of the sham group. Histological evaluation of the tissues also demonstrated a decrease in axonal damage, neuronal degeneration, and glial cell infiltration after curcumin administration.

Conclusions

Although further studies including different dose regimens and time intervals are required, curcumin could attenuate a spinal cord ischemia-reperfusion injury in rabbits via reducing oxidative products and proinflammatory cytokines, as well as increasing activities of antioxidant enzymes and preventing apoptotic cell death.

The value of signal peptide-CUB-EGF domain-containing protein 1 and oxidative stress parameters in the diagnosis of acute mesenteric ischemia

OBJECTIVES

This study investigated the diagnostic value of signal peptide-CUB-EGF domain-containing protein 1 (SCUBE-1) and other oxidative stress parameters in the early diagnosis of acute mesenteric ischemia, which has high mortality and morbidity if not identified and treated in the early period.

METHODS

Thirty-six female Sprague-Dawley rats were used in this randomized, controlled study. Rats were divided into six groups: three control groups (Groups I, III, and V) and three ischemia groups (Groups II, IV, and VI). In the control groups, blood and tissue specimens were sampled at 30 minutes (Group I), 2 hours (Group III), and 6 hours (Group V), following a simple laparotomy. In the ischemia groups, the superior mesenteric artery (SMA) was ligated following laparotomy, and blood and tissue samples were sampled at 30 minutes (Group II), 2 hours (Group IV), and 6 hours (Group VI).

RESULTS

When comparing the ischemia and control groups, the differences in SCUBE-1, malondialdehyde (MDA), and total antioxidant status (TAS) levels in the 30-minute period were not significant (p > 0.05); at 2 hours, SCUBE-1 levels rose rapidly, and although the desired level of significance could not be obtained with Bonferroni correction, the level was significantly higher compared to the control group at the same time interval (for SCUBE-1, Group III vs. Group IV, p = 0.006). In these periods (30 minutes and 2 hours), only total oxidative status (TOS) and oxidative stress index (OSI) values were significantly higher in the ischemia group compared to the control group (for both, p = 0.004). A pronounced rise in SCUBE-1 levels was determined with 6-hour ischemia (for SCUBE-1, Group V vs. Group VI, p = 0.004). The changes in MDA, TAS, TOS, and OSI levels were not significant (p = 0.025, p = 0.321, p = 0.006, and p = 0.037, respectively).

CONCLUSIONS

SCUBE-1 levels have the potential to be used as a marker of early period injury in acute mesenteric ischemia, although it is impossible to state explicitly that they can be used for early diagnosis. The same can be said for plasma MDA and TAS levels. The authors believe that TOS and OSI levels, however, can be used in early diagnosis and as an injury marker. Moreover, OSI also exhibits a medium-strong correlation with histopathologic injury.

Gabapentin is neuroprotective through glutamate receptor-independent mechanisms in staurosporine-induced apoptosis of cultured rat cerebellar neurons

The anticonvulsants that are currently available modulate the activity of neuronal receptors and ion channels, which are equally involved in apoptotic pathways. We investigated the hypothesis that gabapentin (GP), an anticonvulsant without effect on glutamate receptors acting as GABA analog, has neuroprotective properties. For comparison, we chose topiramate (TPM), which has been reported to be neuroprotective via AMPA receptors blockade. For this purpose, we used rat cerebellar granule neuron (CGN) cultures and we triggered apoptosis independent of glutamate receptors with staurosporine, a broad-spectrum protein kinase inhibitor. GP at therapeutic range concentration significantly increased cell viability in CGN cultures maintained in physiological KCl concentration and reversed apoptosis induced by staurosporine. Blockade of NMDA or AMPA receptors by MK801 or NBQX, respectively, did not alter GP neuroprotection, which was reversed instead by GABA. In contrast, protective effect of TPM on STS-treated CGN cultures was annihilated by NBQX, and not altered by MK801 or GABA. Treatments with neuroprotective concentrations of GP or TPM did not modify the expression of neuronal cell adhesion molecule or synaptophysin or the morphological aspect of neuronal endings. In summary, we report that GP is neuroprotective through glutamate-receptor independent mechanisms and without alteration of neuronal plasticity markers, which makes it a possible candidate for clinical neuroprotection trials.

Gabapentin decreases epileptiform discharges in a chronic model of neocortical trauma

Gabapentin (GBP) is an anticonvulsant that acts at the α2δ-1 submit of the L-type calcium channel. It is recently reported that GBP is a potent inhibitor of thrombospondin (TSP)-induced excitatory synapse formation in vitro and in vivo. Here we studied effects of chronic GBP administration on epileptogenesis in the partial cortical isolation ("undercut") model of posttraumatic epilepsy, in which abnormal axonal sprouting and aberrant synaptogenesis contribute to occurrence of epileptiform discharges. Results showed that 1) the incidence of evoked epileptiform discharges in undercut cortical slices studied 1 day or ~2 weeks after the last GBP dose, was significantly reduced by GBP treatments, beginning on the day of injury; 2) the expression of GFAP and TSP1 protein, as well as the number of FJC stained cells was decreased in GBP treated undercut animals; 3) in vivo GBP treatment of rats with undercuts for 3 or 7 days decreased the density of vGlut1-PSD95 close appositions (presumed synapses) in comparison to saline treated controls with similar lesions;4) the electrophysiological data are compatible with the above anatomical changes, showing decreases in mEPSC and sEPSC frequency in the GBP treated animals. These results indicate that chronic administration of GBP after cortical injury is antiepileptogenic in the undercut model of post-traumatic epilepsy, perhaps by both neuroprotective actions and decreases in excitatory synapse formation. The findings may suggest the potential use of GBP as an antiepileptogenic agent following traumatic brain injury.