Evaluation of GABA system and cell damage in parahippocampus of patients with temporal lobe epilepsy showing antiepileptic effects after subacute electrical stimulation.

PURPOSE: The gamma-aminobutyric acid (GABA) system and neuronal loss were evaluated in the parahippocampal cortex (PHC) of patients with intractable mesial temporal lobe epilepsy (MTLE) who received subacute electrical stimulation and showed antiepileptic effects. METHODS: GABA tissue content, GABA(A) and benzodiazepine (BZD) receptor levels, as well as neuronal density were determined in PHC of five patients (ESAE group) with an MTLE history of 14.8 +/- 2.5 years and seizure frequency of 11 +/- 2.9 per month, two (40%) of them with mesial sclerosis. This group demonstrated antiepileptic effects after subacute electrical stimulation (130 Hz, 450 micros, 200-400 microA), applied continuously during 16 to 20 days in PHC. Values were compared with those obtained from patients with severe MTLE (history of 21.7 +/- 2.8 years and seizure frequency of 28.2 +/- 14 per month) in whom electrical stimulation did not induce antiepileptic effects (ESWAE group, n = 4), patients with MTLE in whom no electrical stimulation was applied (MTLE group, n = 4), and autopsy material acquired from subjects without epilepsy (n = 4 obtained from three subjects). RESULTS: The ESAE group demonstrated high GABA tissue levels (219%), as well as a significantly higher cell count (58.5%) when compared with the MTLE group. The ESWAE group showed enhanced BZD-receptor levels (38%), whereas their values for GABA tissue levels and GABA(A) receptor were similar to those obtained from the MTLE group. CONCLUSIONS: It is suggested that subacute electrical stimulation of PHC is more effective in patients with less severe epilepsy, an effect associated with a high GABA tissue content and a low rate of cell loss.

Evaluation of opioid peptide and muscarinic receptors in human epileptogenic neocortex: an autoradiography study.

PURPOSE: The main goal of the present study was to evaluate possible alterations in opioid peptide and muscarinic receptors in human neocortical epileptic focus and the surrounding area removed from patients with pharmacologically resistant epilepsy and epilepsy secondary to cerebral lesion by tumor or other causes. METHODS: In vitro quantitative autoradiography experiments were carried out to label mu, delta, and muscarinic receptors of neocortical epileptic focus and surrounding area obtained from patients with pharmacologically resistant primary epilepsy and epilepsy caused by tumors and angioma cavernosa, and compared with neocortex obtained from patients with dementia and tumors without epilepsy. RESULTS: The mu receptor levels were lower in surrounding areas (-46%). The delta receptor binding was reduced in epileptic focus obtained from patients with epilepsy secondary to cerebral lesion (-25%) and surrounding areas (-31%). In contrast, muscarinic receptor levels were higher in the focus from patients with primary epilepsy (layers I-II, 52%; layers III-IV, 44%; layers V-VI, 36%). CONCLUSIONS: It is suggested that the increased muscarinic receptors in the epileptic focus and the decreased mu and delta receptors in the surrounding area are associated with the initiation and propagation of seizure activity in human epileptogenic neocortex.

Activación del sistema de los opiodes endógenos por dosis subconvulsivamantes de metrazol / Activation of the endogenous opioid system with metrazol subconvulsivant dosis

Se investigaron las alteraciones en el sistema de los opioides endógenos en el cerebro de la rata, inducidas por la administración de una dósis subconvulsivante de metrazol (PTZ) (30 mg/kg i.p.). Por medio de experimentos de microdiálisis, encontramos durante los primeros 60 min después del tratamiento, una liberación importante de opiodes endógenos en el hipocampo y la amígdala cerebral. Posteriormente, los valores regresaron a los niveles basales. Por autorradiografía se observó un decremento en los niveles de los receptores mu en varias estructuras cerebrales. Mediante el análisis de la unión a receptores las membranas cerebrales, se confirmó un decremento en el número de estos receptores, sin cambios en su afinidad. En la aplicación de la prueba de Randall-Sellito, se encontró un aumento en el umbral de respuesta a estímulos dolorosos, durante los primeros 30 min. después del PTZ. Finalmente, experimentos de hibridación in situ revelaron un incremento en los niveles de la proencefalina a las 24 hrs después del tratamiento. Nuestros resultados indican que la administración de dosis subconvulsivante de PTZ activan de manera importante al sistema de los opiodes endógenos. Estos cambios resultan relevantes para entender el proceso del epileptogénesis y los mecanismos involucrados en el mismo

Localization of the microelectrode tip combining a rapid procedure method and marking with pontamine sky blue

Uno de los aspectos más relevantes del registro de la actividad unitaria celular en mamíferos, es la localización precisa de los sitios registrados. El asignar a las neuronas o grupos neuronales una colección definida, muchas veces permite establecer la función que estas estructuras tienen en el SNC. Es por esto que hemos desarrollado un método para identificar las neuromas estudiadas, utilizando micropipetas de vidrio que contienen una solución de azul de pontamina al 4% ne KCL 1M. Al finalizar los registros de actividad neuronal unitaria se hace una inyección iontofeorética, se sacrifican los animales, se fijan y se corta el tejido en microtomo de congelación. Se aplica la técnica de procedimiento rápido para obtener una fotografía de la zona de interés. Este método es fácil y rapido de realizar, y tiene la ventaja de que los mismos cortes del tejido pueden ser usados para procedimientos histológicos posteriores