Pharmacoresistant temporal lobe epilepsy modifies histamine turnover and H3 receptor function in the human hippocampus and temporal neocortex.

Experiments were designed to evaluate the tissue content of tele-methylhistamine (t-MeHA) and histamine as well as H3 receptor (H3 Rs) binding and activation of the heterotrimeric guanine nucleotide binding αi/o proteins (Gαi/o) coupled to these receptors in the hippocampus and temporal neocortex of patients (n = 10) with pharmacoresistant mesial temporal lobe epilepsy (MTLE). Patients with MTLE showed elevated tissue content of t-MeHA in the hippocampus. Analyses revealed that a younger age at seizure onset was correlated with a higher tissue content of t-MeHA, lower H3 R binding, and lower efficacy of Gαi/o protein activation in the hippocampus. We conclude that the hippocampus shows a reduction in the H3 R function associated with enhanced histamine. In contrast, the temporal neocortex displayed a high efficacy of H3 Rs Gαi/o protein activation that was associated with low tissue contents of histamine and t-MeHA. These results indicate an overactivation of H3 Rs leading to decreased histamine in the temporal neocortex. However, this situation was lessened in circumstances such as a longer duration of epilepsy or higher seizure frequency. It is concluded that decrease in H3 Rs function and enhanced levels of histamine may contribute to the epileptic activity in the hippocampus and temporal neocortex of patients with pharmacoresistant MTLE.

Absence of linear correlation between fluctuations in area of simultaneous recorded monosynaptic responses and Hoffmann's reflexes in the rat.

In this study we analyze the possible relationship between fluctuations in area of monosynaptic reflex responses (MSR) and Hoffmann's reflex (H reflexes) in the plantar closed loop pathway of the anesthetized rat. These reflexes were evoked by low-frequency stimuli applied to the sciatic nerve or lateral plantar nerve and then concurrently recorded on the distal tibial nerve or lateral plantar nerve, respectively as well as the lateral plantar muscles in the foot of the anesthetized rat. From trial to trial, H reflexes showed higher variability in area than MSR, whether the latter was recorded in the distal tibial nerve (n=8 experiments) or in the lateral plantar nerve (n=5 experiments). No linear correlation was found between changes in area of concurrently evoked MSR and H reflexes (r(MSR-H,n=8)=0.11+/-0.03 and r(MSR-H,n=5)=0.08+/-0.09, respectively). These findings suggest that trial-to-trial fluctuations in area of H reflexes may involve interaction of several sources of variation, among others to MSR variability (due to pre-, and post-synaptic factors influencing the excitability of spinal motoneurons) in combination with those related to peripheral mechanisms, such as trial to trial activation of a different number of muscle fibers, either by the probabilistic transmitter release from neuromuscular junctions, by activation of motor units of variable size or to fluctuations in excitability of muscle fibers.

Enfermedades neurodegenerativas que cursan con demencia / Demential in the course of neurodegenerative diseases

La demencia es el resultado de la disfunción y la muerte de células del sistema nervioso central y periférico. Con etiología diversa, se inicia de una manera insidiosa y se manifiesta por un agotamiento progresivo y simétrico de las neuronas que producen déficit cognoscitivo múltiple, que desemboca en deterioro de la capacidad para aprender y tendencia a olvidar lo aprendido. Entre las enfermedades neurodegenerativas que cursan con demencia están: Alzheimer, Parkinson, Huntington, Pick, Creutzfeld-Jakob y demencías de etiologías múltiples. La población con una mayor predisposición a padecerlas es la que se encuentra por arriba de los 50 años de edad, lo que coincide con una disminución de la concentración sanguínea de hormonas gonadales, uno de los diversos factores de riesgo. Entre las áreas anatómicas más comúnmente afectadas se encuentran el hipocampo, las áreas motoras primaria y somatosensorial, algunas estructuras del sistema límbico, las cortezas parieto-temporal, frontal y entorrinal. Se sugiere que la patología de esta última área es la responsable de la alteración olfatoria temprana que presentan después de la instalación de la enfermedad, como ha sido reportado para las enfermedades de Alzheimer y Parkinson entre otras, citándose la posibilidad de que esta disfunción sirva como un detector temprano de enfermedades neurodegenerativas.

Participación del sistema olfatorio en la regulación de la ingesta de alimentos / Participation of the olfactory system in the control of intake of food

Se registraron potenciales provocados por estimulación del nervio vago cervical en el bulbo olfatorio (BO), hipotálamo lateral (HL) y la porción rostral del núcleo del tracto solitario (NTS). Se observó que el componente lento del potencial provocado registrado en el BO, correspondía a la capa periglomerular, en cambio el componente previo con una latencia de 4 ms, sólo era registrado en la capa profunda del bulbo olfatorio, probablemente correspondía a la actividad de la capa glomerular. Se encontró que el potencial provocado registrado a nivel del BO, por estimulación del nervio vago, era suprimido por la lesión del NTS, en cambio el potencial registrado en el HL, no sufría cambio alguno. Los resultados aquí presentados, apoyan la idea de una proyección visceral al BO con relevo en el NTS. Se discuten las implicaciones funcionales de esta vía.