Glutamate and gamma-aminobutyric acid content and release of synaptosomes from temporal lobe epilepsy patients

Relationship between fluid-attenuated inversion-recovery (FLAIR) signal intensity and inflammatory mediator's levels in the hippocampus of patients with temporal lobe epilepsy and mesial temporal sclerosis

We investigated a relationship between the FLAIR signal found in mesial temporal sclerosis (MTS) and inflammation. Twenty nine patients were selected through clinical and MRI analysis and submitted to cortico-amygdalo-hippocampectomy to seizure control. Glutamate, TNFα, IL1, nitric oxide (NO) levels and immunostaining against IL1β and CD45 was performed. Control tissues (n=10) were obtained after autopsy of patients without neurological disorders. The glutamate was decreased in the temporal lobe epilepsy (TLE) -MTS group (p<0.001), suggesting increased release of this neurotransmitter. The IL1β and TNFα were increased in the hippocampus (p<0.05) demonstrating an active inflammatory process. A positive linear correlation between FLAIR signal and NO and IL1β levels and a negative linear correlation between FLAIR signal and glutamate concentration was found. Lymphocytes infiltrates were present in hippocampi of TLE patients. These data showed an association between hippocampal signal alteration and increased inflammatory markers in TLE-MTS.

Effects of vigabatrin on brain GABA+/Cr signals in focus-distant and focus-near brain regions monitored by 1H-NMR spectroscopy

The new antiepileptic drug vigabatrin (VGB) increases gamma-aminobutyric acid (GABA) in the brain. We compared GABA+/Cr signals measured focus-near and focus-distant and correlated it with the degree of response to VGB. Brain GABA+/Cr signals were measured in 17 epileptic patients in structurally normal appearing tissue by nuclear proton magnetic resonance (1H-NMR) spectroscopy using a special editing sequence for GABA. In 11 patients the measurements were done in brain areas distant to focus and in six near to focus. Full-responders (seizure reduction of >or=50% at the end of the treatment phase) and partial-responders (seizure reduction of >or=50% at the end of the first month of treatment but <or=50% at end of treatment) had lower GABA+/Cr signals in the hemisphere with the epileptogenic focus and increases of the GABA+/Cr signals with VGB. Non-responders (seizure reduction of <or=50%) had no side difference in the GABA+/Cr signals before treatment and no increase during treatment. These observations were made in structurally normal appearing tissue near to the focus and distant to the focus. A side difference in brain GABA+/Cr signal between the epileptogenic and non-epileptogenic hemisphere before VGB treatment correlates with an improved seizure control under VGB treatment regardless whether the measurement is done focus-near or focus-distant.

Sevoflurane reduces synaptic glutamate release in human synaptosomes

Volatile anesthetics reduce excitatory synaptic transmission in the mammalian brain. In the present study, the effect of sevoflurane on synaptic glutamate release, free cytosolic Ca2+ ([Ca2+]i), and glutamate uptake was investigated using isolated presynaptic terminals prepared from human cerebral cortex. The tissue was obtained from standard temporal lobe specimens removed because of epilepsy. The glutamate release and [Ca2+]i was measured as the fluorescence of nicotinamide adenine dinucleotide phosphate (NADPH) and fura-2, respectively. The uptake of radiolabeled glutamate was measured in a beta-scintillation counter. Membrane depolarization with 4-aminopyridine for three minutes evoked a Ca2+-dependent glutamate release of 3.4 +/- 0.5 nmol/mg. Sevoflurane 2.5 and 4.0% attenuated the evoked release by 45 and 55%, respectively. The evoked increase in [Ca2+]i was not significantly altered by the anesthetic agent. The uptake studies were performed in the high-affinity area, and Km was calculated to 19.3 +/- 5.7 x 10(-6) M and Vmax to 5.7 +/- 1.0 micromol g(-1) min(-1). The Km and Vmax values were not significantly altered by sevoflurane 2.5%. These results demonstrate that sevoflurane in the human brain reduces Ca2+-dependent glutamate release. The exact mode of action is still to be resolved.