Potentiation of panic-like behaviors of the rat by subconvulsive doses of strychnine

Hereditary convulsions in an outbred prairie vole line

Patients with epilepsy are significantly burdened by the disease due to long-term health risks, the severe side effect profiles of anti-epileptic drugs, and the strong possibility of pharmacoresistant refractory seizures. New animal models of epilepsy with unique characteristics promise to further research to address these ongoing problems. Here, we characterize a newly developed line of prairie voles (Microtus ochrogaster, UTol:HIC or "Toledo" line) that presents with a hereditary, adult-onset, handling-induced convulsion phenotype. Toledo voles were bred for four generations and tested to determine whether the observed phenotype was consistent with epileptic seizures. Toledo voles maintained a stable 22 % incidence of convulsions across generations, with an average age of onset of 12-16 weeks. Convulsions in Toledo voles were reliably evoked by rodent seizure screens and were phenotypically consistent with murine seizures. At the colony level, Toledo voles had a 7-fold increase in risk for sudden unexpected death from unknown causes, which parallels sudden unexpected death in epilepsy (SUDEP) in human patients. Finally, convulsions in Toledo voles were reduced or prevented by treatment with the anti-epileptic drug levetiracetam. Taken in combination, these results suggest that convulsions in Toledo voles may be epileptic seizures. The Toledo prairie vole strain may serve as a new rodent model of epilepsy in an undomesticated, outbred species.

A non-ionotropic activity of NMDA receptors contributes to glycine-induced neuroprotection in cerebral ischemia-reperfusion injury

NMDA receptor (NMDAR) is known for its ionotropic function. But recent evidence suggests that NMDAR also has a non-ionotropic property. To determine the role of non-ionotropic activity of NMDARs in clinical relevant conditions, we tested the effect of glycine, a co-agonist of NMDARs, in rat middle cerebral artery occlusion (MCAO), an animal model of cerebral ischemia-reperfusion injury after the animals were injected with the NMDAR channel blocker MK-801 and the glycine receptor antagonist strychnine. We show that glycine reduces the infarct volume in the brain of ischemic stroke animals pre-injected with MK-801 and strychnine. The effect of glycine is sensitive to the antagonist of glycine-GluN1 binding site and blocked by Akt inhibition. In the neurobehavioral tests, glycine improves the functional recovery of stroke animals pre-injected with MK-801 and strychnine. This study suggests that glycine-induced neuroprotection is mediated in part by the non-ionotropic activity of NMDARs via Akt activation in cerebral ischemia-reperfusion injury.

Trigeminal Inflammatory Compression (TIC) injury induces chronic facial pain and susceptibility to anxiety-related behaviors

Our laboratory previously developed a novel neuropathic and inflammatory facial pain model for mice referred to as the Trigeminal Inflammatory Compression (TIC) model. Rather than inducing whole nerve ischemia and neuronal loss, this injury induces only slight peripheral nerve demyelination triggering long-term mechanical allodynia and cold hypersensitivity on the ipsilateral whisker pad. The aim of the present study is to further characterize the phenotype of the TIC injury model using specific behavioral assays (i.e. light-dark box, open field exploratory activity, and elevated plus maze) to explore pain- and anxiety-like behaviors associated with this model. Our findings determined that the TIC injury produces hypersensitivity 100% of the time after surgery that persists at least 21 weeks post injury (until the animals are euthanized). Three receptive field sensitivity pattern variations in mice with TIC injury are specified. Animals with TIC injury begin displaying anxiety-like behavior in the light-dark box preference and open field exploratory tests at week eight post injury as compared to sham and naïve animals. Panic anxiety-like behavior was shown in the elevated plus maze in mice with TIC injury if the test was preceded with acoustic startle. Thus, in addition to mechanical and cold hypersensitivity, the present study identified significant anxiety-like behaviors in mice with TIC injury resembling the clinical symptomatology and psychosocial impairments of patients with chronic facial pain. Overall, the TIC injury model's chronicity, reproducibility, and reliability in producing pain- and anxiety-like behaviors demonstrate its usefulness as a chronic neuropathic facial pain model.

Sleep and epilepsy: exploring an intriguing relationship with a translational approach

The relationship between sleep and epilepsy has been well established. There is a high prevalence of sleep disturbances in epilepsy, which are associated with a decreased quality of life of individuals with epilepsy. In view of this fact, preclinical research is necessary to address many gaps in knowledge. For instance, it is well known that sleep deprivation can trigger seizures; however, this is a complex pathophysiological event. In this context, there are many valuable animal models of epilepsy that reproduce clinical symptoms and can be used. Investigations using animal models that simulate clinical epilepsy are imperative. Furthermore, preclinical studies that reveal mechanisms related to sleep-epilepsy interactions are very important. Results of such studies can, in turn, improve the understanding of epilepsy itself and can be useful in developing new antiepileptic drugs and preventive measures to control seizures. Preclinical research should be performed using a translational framework with experimental designs that can lead to advances in the quality of life of individuals with epilepsy. In view of the fact that more than 50 million of people are affected by epilepsy around the world, understanding the relationship between sleep and epilepsy is imperative.

The effects of paradoxical sleep deprivation on estrous cycles of the female rats

The present purpose was to examine how sleep deprivation affects the estrous cycle of the female rat. Paradoxical sleep-deprived (PSD) adult female Wistar rats were compared to home-cage control (CTRL) on their estrous cyclicity. Forty-four PSD and forty-four CTRL female rats were distributed into 4 subgroups of 11 animals each according to the phase of estrous cycle and were subjected to sleep deprivation for 96 h by the multiple platform technique. After PSD period, vaginal estrous cycles were taken for an additional 9 days. Animals that were submitted to PSD in diestrus phase (PSD-diestrus) had their estrous cycles disrupted during the recovery period by showing a constant diestrus during the first week. As for hormone alterations, progesterone concentrations were statistically higher in PSD-diestrus compared to respective phase control and to PSD-proestrus and PSD-estrus rats while CTRL-metestrus had higher levels than CTRL-proestrus and estrus groups. Testosterone was significantly decreased in PSD-estrus in relation to PSD-proestrus and PSD-diestrus groups and was lower in CTRL-diestrus rats than in home-cage rats in proestrus. In addition, PSD-diestrus phase exhibited higher concentrations of corticosterone and lower estrogen than the respective control rats. These data indicate that PSD may modulate the ovarian hormone release through alterations in hormonal-neurochemical mechanisms.

Anxiety levels and wild running susceptibility in rats: assessment with elevated plus maze test and predator odor exposure

It is reported in the literature that nearly 20% of rats are susceptible to displays of wild running (WR) behavior when submitted to high intensity acoustic stimulation. Some characteristics of WR suggest that it can be viewed as a panic-like reaction. This work aimed to test whether WR-sensitive rats show higher levels of anxiety in elevated-plus-maze (EPM) and predator-odor exposure paradigms in comparison with WR-resistant ones. Male adult Wistar rats were submitted to two trials of acoustic stimulation (104 dB, 60 s) in order to assess WR susceptibility. Seven WR-sensitive and 15 WR-resistant rats were evaluated by the EPM test. Other 13 WR-sensitive and 18 WR-resistant animals were submitted to the predator-odor exposure test which consisted of a 10 min-session of free exploration in a specific apparatus containing two odoriferous stimuli: cotton swab imbedded with snake cloacal gland secretion or with iguana feces (control). WR-sensitive rats presented a significantly higher closed-to open-arm-entry ratio in the EPM test. All rats responded with anxiety-like behaviors to the predator odor exposure, although the WR-sensitive ones showed a marked behavioral inhibition regardless of the odor condition. We conclude that WR-sensitive rats present elevated levels of anxiety manifested by means of passive behavioral strategies.