Levetiracetam (ucb LO59) affects in vitro models of epilepsy in CA3 pyramidal neurons without altering normal synaptic transmission.
ABSTRACT Previous behavioural and electrophysiological studies have indicated that levetiracetam (ucb LO59) acts as an anticonvulsant drug in vivo. The purpose of the present study was to investigate the effects of levetiracetam on normal synaptic transmission and epileptiform activity in vitro. Intracellular recordings were obtained from the CA3 subfield of the rat hippocampal slice preparation. Levetiracetam in a concentration of 10 microM did not influence basic cell properties or normal synaptic transmission evoked by subthreshold and suprathreshold stimuli to the commissural pathway. However, it strongly inhibited the development of epileptiform bursting by the gamma-aminobutyric acid (GABA)A-receptor antagonist bicuculline (1-30 microM). Levetiracetam also decreased the size of bursts previously established by bicuculline. In experiments in which the glutamate-receptor agonist N-Methyl-D-Aspartate (NMDA) was used to generate spontaneous bursting, levetiracetam had no effect on the size of the bursts but decreased bursting frequency. The difference in effects of levetiracetam on bicuculline- and NMDA-induced bursting appeared to be dependent on the convulsant used, since in the presence of 10 microM bicuculline, levetiracetam decreased the size of NMDA-bursts to the same extent as the size of synaptically evoked bicuculline-bursts but had little effect on bursting frequency. The results show that under our experimental conditions, levetiracetam did not alter the components of normal synaptic transmission. However, levetiracetam at the concentrations studied inhibited epileptiform bursting induced by bicuculline and NMDA in vitro in a manner consistent with the profile of an antiepileptogenic drug.
- [show abstract] [hide abstract]
ABSTRACT: The novel anticonvulsant drug ucb L059 ((S)-alpha-ethyl-2-oxo-1-pyrrolidineacetamide) was evaluated in several rodent models of partial and generalized seizures. Ucb L059 (27-108 mg/kg i.p.) increased the thresholds for tonic electroconvulsions and myoclonic and clonic seizures induced by timed i.v. infusion of pentylenetetrazol (PTZ), but was ineffective in the traditional maximal electroshock seizure and s.c. PTZ seizure tests in mice and rats in doses up to 500 mg/kg. The anticonvulsant potency of ucb L059 in seizure threshold tests was similar to that of standard drugs, such as valproate. In amygdala-kindled rats, ucb L059 exerted potent anticonvulsant activity against both focal and secondarily generalized seizures at doses of 13-108 mg/kg. The adverse effects of ucb L059 were quantitated in the open field and in standard tests for motor impairment, such as the rotarod and chimney tests. Ucb L059 exerted only minimal effects on behaviour, e.g. slight hyperactivity, and did not impair muscle activity in the rotarod test in doses up to 1700 mg/kg i.p. The data indicate that ucb L059 is an interesting new anticonvulsant agent with a broad spectrum of activity and high therapeutic index.European Journal of Pharmacology 04/1993; 232(2-3):147-58. · 2.59 Impact Factor
- [show abstract] [hide abstract]
ABSTRACT: Local diffusion of bicuculline from a bicuculline-containing recording micropipette increased the orthodromic field population spike (PS2), elicited upon commissural stimulation in the hippocampal CA3 region of anaesthetized rats. This increase in PS2 was consistently reduced by 5.4 mg/kg of the novel anticonvulsant drug ucb L059 ((S)-alpha-ethyl-2-oxo-pyrrolidine acetamide), when injected i.v. 10 min prior to lowering in place the bicuculline-containing micropipette. ucb L059 had no effect on PS2 in the absence of bicuculline. Paired-pulse stimulation produced marked inhibition of the second PS2 at low interstimulus interval, an effect which was significantly reduced by bicuculline. Although ucb L059 reduced the effect of bicuculline on both PS2S elicited by paired stimulations, the drug did not alter the reduction by bicuculline of paired-pulse inhibition at low interstimulus interval. These results suggest that ucb L059 prevents increases in CA3 neuronal excitability by bicuculline through a non gamma-aminobutyric acid-ergic mechanism.European Journal of Pharmacology 12/1995; 286(3):321-5. · 2.59 Impact Factor
- [show abstract] [hide abstract]
ABSTRACT: A recent study has described synchronous burst discharges of dentate hilar neurons and area CA3 pyramidal cells in the presence of the convulsants 4-aminopyridine and picrotoxin in guinea-pig hippocampal slices [Müller W. and Misgeld U. (1991) J. Neurophysiol. 65, 141-147]. To examine the synchronous activity of dentate cells and area CA3 pyramidal cells further, epileptiform burst discharges were examined in morphologically and/or electrophysiologically identified non-granule cells in the hilus and granule cell layer of the rat dentate gyrus and compared to simultaneously-recorded pyramidal cells of area CA3a, b, and c. Specifically, the types of dentate cells and the types of discharge were examined, as well as the timing of burst discharge of dentate cells relative to different cells of area CA3. In the presence of the GABAA receptor antagonist bicuculline (30 microM), all dentate cell types discharged in rhythmic, spontaneous bursts that were synchronized with area CA3 pyramidal cell epileptiform bursts. The sampled cells included hilar "mossy" cells, hilar fast-spiking cells (putative interneurons) as well as interneurons located in the granule cell layer, such as the pyramidal "basket" cells. Simultaneous recording from dentate non-granule cells and area CA3 pyramidal cells during exposure to bicuculline demonstrated that stimulus-evoked and spontaneous epileptiform bursts occurred almost exactly at the same time; there were only a few milliseconds between the onsets of pyramidal cell bursts and dentate cell bursts, with the pyramidal cell preceding the dentate cell in almost every case. There were no systematic differences among dentate cell types in the extent they lagged behind pyramidal cells, and there were no detectable differences among area CA3 pyramidal cells. In slices that were cut between area CA3 and the dentate gyrus, epileptiform bursts occurred in area CA3 but not in the dentate. These findings suggest that, in the absence of GABAA receptor-mediated inhibition, excitatory pathways from area CA3 to the dentate gyrus are strong and widespread. These pathways, and possibly other mechanisms, can lead to tightly synchronized action potential discharge of pyramidal cells and dentate non-granule cells. The results also suggest that disinhibition alone is insufficient to cause synchronous bursts in the dentate gyrus, in contrast to area CA3.Neuroscience 04/1994; 59(2):245-57. · 3.12 Impact Factor