Maciej Gasior

Neuroprotective and disease-modifying effects of the ketogenic diet.

The ketogenic diet has been in clinical use for over 80 years, primarily for the symptomatic treatment of epilepsy. A recent clinical study has raised the possibility that exposure to the ketogenic diet may confer long-lasting therapeutic benefits for patients with epilepsy. Moreover, there is evidence from uncontrolled clinical trials and studies in animal models that the ketogenic diet can provide symptomatic and disease-modifying activity in a broad range of neurodegenerative disorders including Alzheimers disease and Parkinsons disease, and may also be protective in traumatic brain injury and stroke. These observations are supported by studies in animal models and isolated cells that show that ketone bodies, especially &bgr;-hydroxybutyrate, confer neuroprotection against diverse types of cellular injury. This review summarizes the experimental, epidemiological and clinical evidence indicating that the ketogenic diet could have beneficial effects in a broad range of brain disorders characterized by the death of neurons. Although the mechanisms are not yet well defined, it is plausible that neuroprotection results from enhanced neuronal energy reserves, which improve the ability of neurons to resist metabolic challenges, and possibly through other actions including antioxidant and anti-inflammatory effects. As the underlying mechanisms become better understood, it will be possible to develop alternative strategies that produce similar or even improved therapeutic effects without the need for exposure to an unpalatable and unhealthy, high-fat diet.

The anticonvulsant activity of acetone, the major ketone body in the ketogenic diet, is not dependent on its metabolites acetol, 1,2-propanediol, methylglyoxal, or pyruvic acid.

Summary:u2002 Background: Acetone, one of the principal ketone bodies elevated during treatment with the ketogenic diet, exhibits anticonvulsant properties that may contribute to the seizure protection conferred by the diet. The anticonvulsant mechanism of acetone is unknown, but it is metabolized to several bioactive substances that could play a role.

Efficacy of the ketogenic diet in the 6-Hz seizure test

Purpose: Since the ketogenic diet is effective in drug‐resistant epilepsies, we sought to determine whether it is active in the 6‐Hz seizure test, which identifies agents with a broader spectrum of activity than conventional antiepileptic screening tests.

Influence of Different Methylxanthines on the Anticonvulsant Action of Common Antiepileptic Drugs in Mice

Summary: The protective activity of carbamazepine (CBZ, 60 min before testing), phenobarbital (PB, 120 ruin), phenytoin (PHT, 120 min), and valproate (VPA, 30 min) alone or concurrent with methylxanthine derivatives was evaluated against maximal electroshock‐induced seizures (MES) in male mice. All drugs were administered intraperitoneally (i.p.), and the protection offered by antiepileptic drugs (AEDs) was expressed as ED50 in mg/kg. Caffeine sodium benzoate in doses of 0.0595‐0.476 mmol/ kg (11.55–92.4 mg/kg) distinctly reduced the anticonvulsant efficacy of PB, in the highest dose tested with an increase in ED50 value from 19.5 to 38 mg/kg. This methylxanthine derivative in the dose range of 0.119‐0.476 mmol/kg (23.1–92.4 mg/kg) also efficiently inhibited the protective action of PHT. When combined with caffeine (0.238 and 0.476 mmol/kg), the ED50 of PHT was raised from 12 to 17 and 24 mg/kg, respectively. In doses of 0.238 and 0.476 mmol/kg, caffeine also diminished the efficacy of CBZ and VPA, and at the highest dose tested the methylxanthine elevated the respective ED50s from 13 to 20.5 mg/kg and from 270 to 420 mg/kg. Generally caffeine sodium benzoate (up to 0.476 mmol/kg) did not affect the plasma levels of studied AEDs, and only at 0.476 mmol/kg did it significantly decrease the level of PHT. Among the other methylxanthines, pentoxifylline (0.238‐0.476 mmol/kg; 66.3–132.5 mg/kg) and diprophylline (0.952 mmol/kg; 242.1 mg/kg) inhibited the protective potential of PHT and the respective ED50 were raised from 12 to 16.5, 15.5, and 14 mg/kg. No significant alterations in PHT plasma levels were observed. Moreover, neither pentoxifylline nor diprophylline affected the antielec‐troshock efficacy of the remaining studied AEDs. The results may suggest that caffeine should be avoided in epileptic patients. Pentoxifylline and diprophylline appear to be less dangerous in patients with epilepsy who must receive methylxanthine medication for reasons other than epilepsy.

Anticonvulsant and proconvulsant actions of 2-deoxy-d-glucose

Purpose:u2002 2‐Deoxy‐d‐glucose (2‐DG), a glucose analog that accumulates in cells and interferes with carbohydrate metabolism by inhibiting glycolytic enzymes, has anticonvulsant actions. Recognizing that severe glucose deprivation can induce seizures, we sought to determine whether acute treatment with 2‐DG can promote seizure susceptibility by assessing its effects on seizure threshold. For comparison, we studied 3‐methyl‐glucose (3‐MG), which like 2‐DG accumulates in cells and reduces glucose uptake, but does not inhibit glycolysis.

Prolonged Attenuation of Amygdala-Kindled Seizure Measures in Rats by Convection-Enhanced Delivery of the N-Type Calcium Channel Antagonists ω-Conotoxin GVIA and ω-Conotoxin MVIIA

Convection-enhanced delivery (CED) permits the homogeneous distribution of therapeutic agents throughout localized regions of the brain parenchyma without causing tissue damage as occurs with bolus injection. Here, we examined whether CED infusion of the N-type calcium channel antagonists ω-conotoxin GVIA (ω-CTX-G) and ω-conotoxin MVIIA (ω-CTX-M) can attenuate kindling measures in fully amygdala-kindled rats. Rats were implanted with a combination infusion cannula-stimulating electrode assembly into the right basolateral amygdala. Fully kindled animals received infusions of vehicle, ω-CTX-G (0.005, 0.05, and 0.5 nmol), ω-CTX-M (0.05, 0.15, and 0.5 nmol), proteolytically inactivated ω-CTX-M (0.5 nmol), or carbamazepine (500 nmol) into the stimulation site. CED of ω-CTX-G and ω-CTX-M over a 20-min period resulted in a dose-dependent increase in the afterdischarge threshold and a decrease in the afterdischarge duration and behavioral seizure score and duration during a period of 20 min to 1 week after the infusion, indicating an inhibitory effect on the triggering and expression of kindled seizures. The protective effects of ω-conotoxins reached a maximum at 48 h postinfusion, and then they gradually resolved over the next 5 days. In contrast, carbamazepine was active at 20 min but not at 24 h after the infusion, whereas CED of vehicle or inactivated ω-CTX-M had no effect. Except for transient tremor in some rats receiving the highest toxin doses, no adverse effects were observed. These results indicate that local CED of high-molecular-weight presynaptic N-type calcium channel blockers can produce long-lasting inhibition of brain excitability and that they may provide prolonged seizure protection in focal seizure disorders.

Pharmacological modulation of GABAB receptors affects cocaine-induced seizures in mice

RationalePrevious data have demonstrated that the convulsant effects of cocaine can be modulated by compounds that increase levels of endogenous γ-aminobutyric acid (GABA) or that directly stimulate GABAA receptors.ObjectivesTo determine whether the convulsant effects of cocaine can be modulated by ligands selective for GABAB receptors in mice.MethodsEffects of the GABAB receptor agonist ((±)-baclofen), antagonist (phaclofen), and their combination were tested against clonic seizures induced by cocaine (75xa0mg/kg). Enantiomers of baclofen were used to confirm stereospecificity of (±)-baclofen’s effects. Pharmacological specificity of (±)-baclofen’s effects was tested by comparison against seizures induced by GBRxa012909 (monoamine transporter inhibitor), pentylenetetrazole (GABAA antagonist), N-methyl-d-aspartate (NMDA agonist), and aminophylline (A1/A2 adenosine antagonist). Additionally, effects of (±)-baclofen on kindled seizures induced by repeated administration of cocaine (60xa0mg/kg every 24xa0h for 6 days) were evaluated. The inverted screen test was used to assess behavioral side effects of baclofen.Results(±)-Baclofen dose-dependently inhibited acute (ED50=4.1xa0mg/kg) and kindled (6.4xa0mg/kg) seizures induced by cocaine at doses somewhat lower than those producing behavioral side effects (11.5xa0mg/kg), and these effects were stereospecific. (±)-Baclofen suppressed seizures induced by GBRxa012909 but not by pentylenetetrazole, NMDA, and aminophylline, suggesting selectivity of its anticonvulsant effects for monoamine-related mechanisms. Finally, phaclofen dose-dependently enhanced the convulsant effects of a threshold dose of cocaine (60xa0mg/kg).ConclusionsModulation of GABAB receptors can affect seizures induced by cocaine. This molecular mechanism may be involved in seizures induced by cocaine or, alternatively, may function as an independent inhibitory mechanism against seizures arising from blockade of monoamine uptake.

Role of GluK1 Kainate Receptors in Seizures, Epileptic Discharges, and Epileptogenesis

Kainate receptors containing the GluK1 subunit have an impact on excitatory and inhibitory neurotransmission in brain regions, such as the amygdala and hippocampus, which are relevant to seizures and epilepsy. Here we used 2-amino-3-(3-hydroxy-5-tert-butylisoxazol-4-yl) propanoic acid (ATPA), a potent and selective agonist of kainate receptors that include the GluK1 subunit, in conjunction with mice deficient in GluK1 and GluK2 kainate receptor subunits to assess the role of GluK1 kainate receptors in provoking seizures and in kindling epileptogenesis. We found that systemic ATPA, acting specifically via GluK1 kainate receptors, causes locomotor arrest and forelimb extension (a unique behavioral characteristic of GluK1 activation) and induces myoclonic behavioral seizures and electrographic seizure discharges in the BLA and hippocampus. In contrast, the proconvulsant activity of systemic AMPA, kainate, and pentylenetetrazol is not mediated by GluK1 kainate receptors, and deletion of these receptors does not elevate the threshold for seizures in the 6 Hz model. ATPA also specifically activates epileptiform discharges in BLA slices in vitro via GluK1 kainate receptors. Olfactory bulb kindling developed similarly in wild-type, GluK1, and GluK2 knock-out mice, demonstrating that GluK1 kainate receptors are not required for epileptogenesis or seizure expression in this model. We conclude that selective activation of kainate receptors containing the GluK1 subunit can trigger seizures, but these receptors are not necessary for seizure generation in models commonly used to identify therapeutic agents for the treatment of epilepsy.

Long-Lasting Attenuation of Amygdala-Kindled Seizures after Convection-Enhanced Delivery of Botulinum Neurotoxins A and B into the Amygdala in Rats

Botulinum neurotoxins (BoNTs) are well recognized to cause potent, selective, and long-lasting neuroparalytic actions by blocking cholinergic neurotransmission to muscles and glands. There is evidence that BoNT isoforms can also inhibit neurotransmission in the brain. In this study, we examined whether locally delivered BoNT/A and BoNT/B can attenuate kindling measures in amygdala-kindled rats. Male rats were implanted with a combination infusion cannula–stimulating electrode assembly into the right basolateral amygdala. Fully kindled animals received a single infusion of vehicle or BoNT/A or BoNT/B at doses of 1, 3.2, or 10 ng over a 20-minute period by convection-enhanced delivery. Electrographic (EEG) and behavioral kindling measures were determined at selected times during the 3- to 64-day period after the infusion. BoNT/B produced a dose-dependent elevation in after-discharge threshold and duration and a reduction in the seizure stage and duration of behavioral seizures that lasted for up to 50 days after infusion. BoNT/A had similar effects on EEG measures; behavioral seizure measures were also reduced, but the effect did not reach statistical significance. The effects of both toxins on EEG and behavioral measures progressively resolved during the latter half of the observation period. Animals gained weight normally, maintained normal body temperature, and did not show altered behavior. This study demonstrates for the first time that locally delivered BoNTs can produce prolonged inhibition of brain excitability, indicating that they could be useful for the treatment of brain disorders, including epilepsy, that would benefit from long-lasting suppression of neurotransmission within a circumscribed brain region.