Does pain sensitivity increase during ictal period? Evidence from absence epileptic WAG/Rij rats

Inherited pain hypersensitivity and increased anxiety-like behaviors are associated with genetic epilepsy in Wistar Audiogenic Rats: Short- and long-term effects of acute and chronic seizures on nociception and anxiety

Anxiety and pain hypersensitivity are neurobehavioral comorbidities commonly reported by patients with epilepsies, and preclinical models are suitable to investigate the neurobiology of behavioral and neuropathological alterations associated with these epilepsy-related comorbidities. This work aimed to characterize endogenous alterations in nociceptive threshold and anxiety-like behaviors in the Wistar Audiogenic Rat (WAR) model of genetic epilepsy. We also assessed the effects of acute and chronic seizures on anxiety and nociception. WARs from acute and chronic seizure protocols were divided into two groups to assess short- and long-term changes in anxiety (1 day or 15 days after seizures, respectively). To assess anxiety-like behaviors, the laboratory animals were submitted to the open field, light-dark box, and elevated plus maze tests. The von Frey, acetone, and hot plate tests were used to measure the endogenous nociception in seizure-free WARs, and postictal antinociception was recorded at 10, 30, 60, 120, 180 min, and 24 h after seizures. Seizure-free WARs presented increased anxiety-like behaviors and pain hypersensitivity, displaying mechanical and thermal allodynia (to heat and cold stimuli) in comparison to nonepileptic Wistar rats. Potent postictal antinociception that persisted for 120 to 180 min was detected after acute and chronic seizures. Additionally, acute and chronic seizures have magnified the expression of anxiety-like behaviors when assessed at 1 day and 15 days after seizures. Behavioral analysis indicated more severe and persistent anxiogenic-like alterations in WARs submitted to acute seizures. Therefore, WARs presented pain hypersensitivity and increased anxiety-like behaviors endogenously associated with genetic epilepsy. Acute and chronic seizures induced postictal antinociception in response to mechanical and thermal stimuli and increased anxiety-like behaviors when assessed 1 day and 15 days later. These findings support the presence of neurobehavioral alterations in subjects with epilepsy and shed light on the use of genetic models to characterize neuropathological and behavioral alterations associated with epilepsy.

Electroencephalographic investigation of the effects of Ginkgo biloba on spike-wave discharges in rats with genetic absence epilepsy

OBJECTIVE

EGb 761, a plant extract obtained from the leaves of the Ginkgo biloba tree, is widely used in modern medicine and traditional medicine applications in the treatment of many diseases. However, in some clinical case reports, it has been suggested that G. biloba causes epileptic seizures. A limited number of experimental animal studies related to the effects of G. biloba on epileptic seizures do not provide sufficient information on the solution of a serious clinical problem with contrasting findings. We aimed to investigate the effects of EGb 761 administered in different doses to adult male Wistar Albino Glaxo/Rijswijk (WAG/Rij) rats which is the genetic animal model of absence epilepsy, on absence seizures using in vivo electrophysiological method. In addition, the effects of EGb 761 doses on locomotor behavior of WAG/Rij rats were evaluated with open-field and rotarod behavioral tests.

METHODS

50, 100, 200, and 400 mg/kg doses of EGb 761 were administered to male WAG/Rij rats with implanted EEG electrodes by oral gavage for 28 days. Evaluation of absence seizures was performed on spike-wave discharges (SWDs) in EEG recorded for 4 h each week. The number of SWDs, the total duration of SWDs, and the mean duration of SWD were determined for the analysis.

RESULTS

In the group treated with 400 mg/kg EGb 761, the number of SWDs and the mean duration of SWD at the 1st and 7th doses and the total duration of SWDs at the 1st, 7th and 14th doses were significantly increased (p < 0.05). In all experimental groups treated with EGb 761 doses, there was no significant change in locomotor activity in the open-field and the rotarod tests.

CONCLUSION

Ginkgo biloba extract EGb 761 increased the epileptic SWD parameters of WAG/Rij rats at high doses (400 mg/kg), causing a pro-epileptic effect on absence seizures. It should be noted that in patients with epilepsy and in high-dose applications, G. biloba extract EGb 761 may lead to an increase in neuronal excitability.

Pain Modulation in WAG/Rij Epileptic Rats (A Genetic Model of Absence Epilepsy): Effects of Biological and Pharmacological Histone Deacetylase Inhibitors

Epigenetic mechanisms are involved in epilepsy and chronic pain development. About that, we studied the effects of the natural histone deacetylase (HDAC) inhibitor sodium butyrate (BUT) in comparison with valproic acid (VPA) in a validated genetic model of generalized absence epilepsy and epileptogenesis. WAG/Rij rats were treated with BUT (30 mg/kg), VPA (300 mg/kg), and their combination (BUT + VPA) daily per os for 6 months. Rats were subjected at Randall–Selitto, von Frey, hot plate, and tail flick tests after 1, 3, and 6 months of treatment to evaluate hypersensitivity to noxious and non-noxiuous stimuli. Moreover, PPAR-γ (G3335 1 mg/kg), GABA-B (CGP35348 80 mg/kg), and opioid (naloxone 1 mg/kg) receptor antagonists were administrated to investigate the possible mechanisms involved in analgesic activity. The expression of NFkB, glutathione reductase, and protein oxidation (carbonylation) was also evaluated by Western blot analysis. WAG/Rij rats showed an altered pain threshold throughout the study (p < 0.001). BUT and BUT + VPA treatment reduced hypersensitivity (p < 0.01). VPA was significantly effective only after 1 month (p < 0.01). All the three receptors are involved in BUT + VPA effects (p < 0.001). BUT and BUT + VPA decreased the expression of NFkB and enhanced glutathione reductase (p < 0.01); protein oxidation (carbonylation) was reduced (p < 0.01). No effect was reported with VPA. In conclusion BUT, alone or in coadministration with VPA, is a valuable candidate for managing the epilepsy-related persistent pain.

Contemporaneous evaluation of patient experience, surgical strategy, and seizure outcomes in patients undergoing stereoelectroencephalography or subdural electrode monitoring

OBJECTIVE

Intracranial electrographic localization of the seizure onset zone (SOZ) can guide surgical approaches for medically refractory epilepsy patients, especially when the presurgical workup is discordant or functional cortical mapping is required. Minimally invasive stereotactic placement of depth electrodes, stereoelectroencephalography (SEEG), has garnered increasing use, but limited data exist to evaluate its postoperative outcomes in the context of the contemporaneous availability of both SEEG and subdural electrode (SDE) monitoring. We aimed to assess the patient experience, surgical intervention, and seizure outcomes associated with these two epileptic focus mapping techniques during a period of rapid adoption of neuromodulatory and ablative epilepsy treatments.

METHODS

We retrospectively reviewed 66 consecutive adult intracranial electrode monitoring cases at our institution between 2014 and 2017. Monitoring was performed with either SEEG (n = 47) or SDEs (n = 19).

RESULTS

Both groups had high rates of SOZ identification (SEEG 91.5%, SDE 88.2%, P = .69). The majority of patients achieved Engel class I (SEEG 29.3%, SDE 35.3%) or II outcomes (SEEG 31.7%, SDE 29.4%) after epilepsy surgery, with no significant difference between groups (P = .79). SEEG patients reported lower median pain scores (P = .03) and required less narcotic pain medication (median = 94.5 vs 594.6 milligram morphine equivalents, P = .0003). Both groups had low rates of symptomatic hemorrhage (SEEG 0%, SDE 5.3%, P = .11). On multivariate logistic regression, undergoing resection or ablation (vs responsive neurostimulation/vagus nerve stimulation) was the only significant independent predictor of a favorable outcome (adjusted odds ratio = 25.4, 95% confidence interval = 3.48-185.7, P = .001).

SIGNIFICANCE

Although both SEEG and SDE monitoring result in favorable seizure control, SEEG has the advantage of superior pain control, decreased narcotic usage, and lack of routine need for intensive care unit stay. Despite a heterogenous collection of epileptic semiologies, seizure outcome was associated with the therapeutic surgical modality and not the intracranial monitoring technique. The potential for an improved postoperative experience makes SEEG a promising method for intracranial electrode monitoring.