Spectral analysis of electrocorticographic activity during pharmacological preconditioning and seizure induction by intrahippocampal domoic acid

In vivo laser speckle contrast imaging of 4-aminopyridine- or pentylenetetrazole-induced seizures

Clinical and preclinical studies on epileptic seizures are closely linked to the study of neurovascular coupling. Obtaining reliable information about cerebral blood flow (CBF) in the area of epileptic activity through minimally invasive techniques is crucial for research in this field. In our studies, we used laser speckle contrast imaging (LSCI) to gather information about the local blood circulation in the area of epileptic activity. We used two models of epileptic seizures: one based on 4-aminopyridine (4-AP) and another based on pentylenetetrazole (PTZ). We verified the duration of an epileptic seizure using electrocorticography (ECoG). We applied the antiepileptic drug topiramate (TPM) to both models, but its effect was different in each case. However, in both models, TPM had an effect on neurovascular coupling in the area of epileptic activity, as shown by both LSCI and ECoG data. We demonstrated that TPM significantly reduced the amplitude of 4-AP-induced epileptic seizures (4-AP+TPM: 0.61 ± 0.13 mV vs 4-AP: 1.08 ± 0.19 mV; p < 0.05), and it also reduced gamma power in ECoG in PTZ-induced epileptic seizures (PTZ+TPM: 38.5% ± 11.9% of the peak value vs PTZ: 59.2% ± 3.0% of peak value; p < 0.05). We also captured the pattern of CBF changes during focal epileptic seizures induced by 4-AP. Our data confirm that the system of simultaneous cortical LSCI and registration of ECoG makes it possible to evaluate the effectiveness of pharmacological agents in various types of epileptic seizures in in vivo models and provides spatial and temporal information on the process of ictogenesis.

Atenolol offers better protection than clonidine against cardiac injury in kainic acid-induced status epilepticus

BACKGROUND AND PURPOSE

Status epilepticus is increasingly associated with cardiac injury in both clinical and animal studies. The current study examined ECG activity for up to 48 h following kainic acid (KA) seizure induction and compared the potential of atenolol and clonidine to attenuate this cardiac pathology.

EXPERIMENTAL APPROACH

Sprague-Dawley rats (male, 300-350 g) were implanted with ECG and electrocorticogram electrodes to allow simultaneous telemetric recordings of cardiac and cortical responses during and after KA-induced seizures. Animals were randomized into saline controls, and saline vehicle-, clonidine- or atenolol-pretreated KA groups.

KEY RESULTS

KA administration in the saline-pretreated group produced an immediate bradycardic response (maximal decrease of 28 ± 6%), coinciding with low-level seizure activity. As high-level seizure behaviours and EEG spiking increased, tachycardia also developed, with a maximum heart rate increase of 38 ± 7% coinciding with QTc prolongation and T wave elevation. Both clonidine and atenolol pretreatment attenuated seizure activity and reduced KA-induced changes in heart rate, QTc interval and T wave amplitude observed during both bradycardic and tachycardic phases in saline-pretreated KA animals. Clonidine, however, failed to reduce the power of EEG frequencies. Atenolol and to a lesser extent clonidine attenuated the cardiac hypercontraction band necrosis, inflammatory infiltration, and oedema at 48 h after KA, relative to the saline-KA group.

CONCLUSIONS AND IMPLICATIONS

Severe seizure activity in this model was clearly associated with altered ECG activity and cardiac pathology. We suggest that modulation of sympathetic activity by atenolol provides a promising cardioprotective approach in status epilepticus.

NMDA preconditioning attenuates cortical and hippocampal seizures induced by intracerebroventricular quinolinic acid infusion

Searching for new therapeutic strategies through modulation of glutamatergic transmission using effective neuroprotective agents is essential. Glutamatergic excitotoxicity is a common factor to neurodegenerative diseases and acute events such as cerebral ischemia, traumatic brain injury, and epilepsy. This study aimed to evaluate behavioral and electroencephalographic (EEG) responses of mice cerebral cortex and hippocampus to subconvulsant and convulsant application of NMDA and quinolinic acid (QA), respectively. Moreover, it aimed to evaluate if EEG responses may be related to the neuroprotective effects of NMDA. Mice were preconditioned with NMDA (75 mg/kg, i.p.) and EEG recordings were performed for 30 min. One day later, QA was injected (36.8 nmol/site) and EEG recordings were performed during 10 min. EEG analysis demonstrated NMDA preconditioning promotes spike-wave discharges (SWDs), but it does not display behavioral manifestation of seizures. Animals that were protected by NMDA preconditioning against QA-induced behavioral seizures, presented higher number of SWD after NMDA administration, in comparison to animals preconditioned with NMDA that did display behavioral seizures after QA infusion. No differences were observed in latency for the first seizure or duration of seizures. EEG recordings after QA infusion demonstrated there were no differences in the number of SWD, latency for the first seizure or duration of seizures in animals pretreated with saline or in animals preconditioned by NMDA that received QA. A negative correlation was identified between the number of NMDA-induced SWD and QA-induced seizures severity. These results suggest a higher activation during NMDA preconditioning diminishes mice probability to display behavioral seizures after QA infusion.

Ischemic cardiomyopathy following seizure induction by domoic Acid

Exposure to the excitotoxin domoic acid (DOM) has been shown to produce cardiac lesions in both clinical and animal studies. We have previously shown that DOM failed to directly affect cardiomyocyte viability and energetics, but the development of this cardiomyopathy has remained unexplained. The present study compared effects of high-level seizure induction obtained by intraperitoneal (2 mg/kg) or intrahippocampal (100 pmol) bolus administration of DOM on development of cardiac pathologies in a rat model. Assessment of cardiac pressure derivatives and coronary flow rates revealed a significant time-dependent decrease in combined left ventricular (LV) systolic and diastolic function at 1, 3, 7, and 14 days after intraperitoneal administration and at 7 and 14 days after intrahippocampal DOM administration. LV dysfunction was matched by a similar time-dependent decrease in mitochondrial respiratory control, associated with increased proton leakage, and in mitochondrial enzyme activities. Microscopic examination of the LV midplane revealed evidence of progressive multifocal ischemic damage within the subendocardial, septal, and papillary regions. Lesions ranged from reversible early damage (vacuolization) to hypercontracture and inflammatory necrosis progressing to fibrotic scarring. Plasma proinflammatory IL-1α, IL-1β, and TNF-α cytokine levels were also increased from 3 days after seizure induction. The observed cardiomyopathies did not differ between intraperitoneal and intrahippocampal groups, providing strong evidence that cardiac damage after DOM exposure is a consequence of a seizure-evoked autonomic response.

Pharmacological Preconditioning with GYKI 52466: A Prophylactic Approach to Neuroprotection

Some toxins and drugs can trigger lasting neuroprotective mechanisms that enable neurons to resist a subsequent severe insult. This “pharmacological preconditioning” has far-reaching implications for conditions in which blood flow to the brain is interrupted. We have previously shown that in vitro preconditioning with the AMPA receptor antagonist GYKI 52466 induces tolerance to kainic acid (KA) toxicity in hippocampus. This effect persists well after washout of the drug and may be mediated via inverse agonism of G-protein coupled receptors (GPCRs). Given the amplifying nature of metabotropic modulation, we hypothesized that GYKI 52466 may be effective in reducing seizure severity at doses well below those normally associated with adverse side effects. Here we report that pharmacological preconditioning with low-dose GYKI imparts a significant protection against KA-induced seizures in vivo. GYKI (3 mg/kg, s.c.), 90–180 min prior to high-dose KA, markedly reduced seizure scores, virtually abolished all level 3 and level 4 seizures, and completely suppressed KA-induced hippocampal c-FOS expression. In addition, preconditioned animals exhibited significant reductions in high frequency/high amplitude spiking and ECoG power in the delta, theta, alpha, and beta bands during KA. Adverse behaviors often associated with higher doses of GYKI were not evident during preconditioning. The fact that GYKI is effective at doses well-below, and at pre-administration intervals well-beyond previous studies, suggests that a classical blockade of ionotropic AMPA receptors does not underlie anticonvulsant effects. Low-dose GYKI preconditioning may represent a novel, prophylactic strategy for neuroprotection in a field almost completely devoid of effective pharmaceuticals.