Accumulating evidence suggests that changes in neuronal chloride homeostasis may be involved in the mechanisms by which brain insults induce the development of epilepsy. A variety of brain insults, including status epilepticus (SE), lead to changes in the expression of the cation-chloride cotransporters KCC2 and NKCC1, resulting in intracellular chloride accumulation and reappearance of immature, depolarizing synaptic responses to GABA A receptor activation, which may critically contribute to the neuronal hyperexcitability underlying epileptogenesis. In the present study, it was evaluated whether prolonged administration of the selective NKCC1 inhibitor, bumetanide, after a pilocarpine-induced SE modifies the development of epilepsy in adult female rats. The antiepileptic drug phenobarbital, either alone or in combination, was used for comparison. Based on pharmacokinetic studies with bumetanide, which showed extremely rapid elimination and low brain penetration of this drug in rats, bumetanide was administered systemically with different dosing protocols, including continuous intravenous infusion. As shown by immunohistochemistry, neuronal NKCC1 expression was markedly upregulated shortly after SE. Prophylactic treatment with phenobarbital after SE reduced the number of rats developing spontaneous seizures and decreased seizure frequency, indicating a disease-modifying effect. Bumetanide did not exert any significant effects on development of spontaneous seizures nor did it enhance the effects of phenobarbital. However, combined treatment with both drugs counteracted several of the behavioral consequences of SE, which was not observed with single drug treatment. These data do not indicate that bumetanide can prevent epilepsy after SE, but the disease-modifying effect of this drug warrants further studies with more lipophilic prodrugs of bumetanide.

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In patients at risk of developing epilepsy after an initial precipitating injury to the brain, the epileptogenic latent period may offer a window of opportunity for initiating potential antiepileptogenic therapy in an attempt to prevent epilepsy from developing. One potential target for antiepileptogenesis is the development of neuronal hyperexcitability during the latent period. Surprisingly, some recent studies in models of temporal lobe epilepsy (TLE) have suggested that proconvulsant drugs could have favourable effects on epileptogenesis, resulting in the proposal of pursuing proconvulsant prophylaxis for epileptogenesis. In the present study, we evaluated this provocative hypothesis by experiments with the GABA(A) receptor antagonist pentylenetetrazole (PTZ) in two TLE models, the intrahippocampal kainate model and the lithium-pilocarpine model in rats. First, we repeatedly determined the PTZ seizure threshold by i.v. infusion of the convulsant during the latent period following intrahippocampal kainate. In line with recent experiments in the lithium-pilocarpine model, the PTZ seizure threshold was significantly decreased over several days following status epilepticus. We then studied whether prolonged infusion of a proconvulsant dose of PTZ at different times after kainate or pilocarpine affected the development of epilepsy. PTZ did not prevent the development of spontaneous recurrent seizures and did not decrease their frequency or severity, but exerted only a moderate disease-modifying effect in that spontaneous seizures in the kainate model were significantly shortened. These data indicate that administration of proconvulsant drugs such as PTZ during the latent period following SE is not a promising strategy for preventing epilepsy.

Deep brain stimulation of the subthalamic nucleus is an effective treatment option for Parkinson's disease. In our lab we established a protocol to screen different neurostimulation patterns in hemiparkinsonian (unilateral lesioned) rats. It consists of creating a unilateral Parkinson's lesion by injecting 6-hydroxydopamine (6-OHDA) into the right medial forebrain bundle, implanting chronic stimulation electrodes into the subthalamic nucleus and evaluating motor outcomes at the end of 24 hr periods of cable-bound external neurostimulation. The stimulation was conducted with constant current stimulation. The amplitude was set 20% below the individual threshold for side effects. The motor outcome evaluation was done by the assessment of spontaneous paw use in the cylinder test according to Shallert and by the assessment of skilled reaching in the staircase test according to Montoya. This protocol describes in detail the training in the staircase box, the cylinder test, as well as the use of both in hemiparkinsonian rats. The use of both tests is necessary, because the staircase test seems to be more sensitive for fine motor skill impairment and exhibits greater sensitivity to change during neurostimulation. The combination of the unilateral Parkinson model and the two behavioral tests allows the assessment of different stimulation parameters in a standardized way.