A direct role of dopamine in the rat subthalamic nucleus and an adjacent intrapeduncular area.

The subthalamic nucleus, a clinically important component of the extrapyramidal motor system, and a lateral area extending into the peduncle contain catecholamine terminals and dopamine receptors coupled to adenylate cyclase. In addition, dopamine agonists administered in vivo enhance glucose utilization in the region. Thus, neuronal function in this region is directly affected by dopamine and dopaminergic drugs.

[Changes in the ultrastructure of the motor zone of the cortex and various areas of the rats pyramidal system in acute toxic action of phenazepam]. / Izmeneniia ul'trastruktury dvigatel'noi zony kory i nekotorykh otdelov ékstrapiramidnoi sistemy krys pri ostrom toksicheskom deistvii fenazepama.

As it was revealed by electron microscopic study, phenazepam (benzodiazepine representative) administered to rats in acute toxic dose caused astrocyte processes swelling mainly in reticular portion of substantia nigra and cerebral areas with high density of GABAergic synapses in initial intoxication stage (one hour after the drug introduction). Following 24 hrs changes of axodendritic and axo-somatic synapse postsynaptic part were detected similar to those of myoneural synapses induced by anti-cholinesterase agents, which allows to suggest the contribution of the increased intracellular calcium ions content. Specific benzodiazepine receptor agonist-flumazenil, introduced 30 min later than phenazepam leaded to the decrease of ultrastructural changes in postsynaptic part of the synapses in reticular zone of substantia nigra. Thus toxic effect of drugs that cause prolonged activity of peripheral and central synapses postsynaptic part results in the alike ultrastructural changes irrespective of their mediator type and is likely to be connected with the growth of intracellular calcium concentration.

[Structural-functional connections of the lemniscus system with the caudate nucleus in the cat]. / Strukturno-funktsional'nye sviazi lemniskovoi sistemy s khvostatym iadrom u koshek.

Afferent projections were studied of nuclei of the spinal cord dorsal columns to the caudate nuclei. Evoked potentials (EPs) were recorded in the caudate nuclei and the nuclei of dorsal columns of the spinal cord to stimulation of the forelimb against the background and after unilateral elimination of the medial lemniscus. After the section, the EPs in the recorded nuclei sharply intensified in response to stimulation of the forelimb, ipsilateral to the section. Degenerative changes were also shown by electron microscopy in axonal terminals in the caudate nuclei at the operated side. Conclusion is drawn that the caudate nuclei receive direct connections from the contralateral nuclei of the spinal cord dorsal columns, which probably, conduct mainly kinesthetic afferent influences.

Análisis ultraestructural comparativo en pacientes con enfermedad de Parkinson y ratas viejas / Ultraestructural comparative analysis between Parkinson disease patients and aged rats

Los pacientes con enfermedad de Parkinson idiopático presentan pérdida neuronal de la sustancia negra parte compacta y la consecuente degeneración de la vía nigroestriatal; por otro lado, se ha reportado que los animales viejos también tienen pérdida de dicha inervación. El objetivo del presente trabajo fue comparar los cambios neurodegenerativos en el neuropilo del núcleo caudado de pacientes parkinsónicos y de animales viejos, con el fin de comparar los cambios que sufre dicho núcleo en los dos procesos degenerativos. En el análisis ultraestructural se utilizaron fragmentos del núcleo caudado de pacientes con enfermedad de Parkinson (n= 4) y de ratas viejas de 36 meses de edad (n= 4), para lo cual se midieron 100 botones presinápticos por caudado y se observó la estructura postsináptica y el número de contactos que establecía el botón con la misma estructura. Los resultados muestran que tanto los pacientes con enfermedad de Parkinson como las ratas viejas presentan un incremento estadisticamente significativo en el tamaño de los botones sinápticos, aumento en el número de contactos axodendríticos y aumento en el número de contactos dobles en comparación con los controles. Los datos indican que los pacientes parkinsónicos presentan alteraciones ultraestructurales similares a las de los animales viejos, alteraciones debidas a la ineficiente inervación dopaminérgica procedente del mesencéfalo, por lo cual se considero que el envejecimiento en animales es un buen modelo para el estudio de la neurodegeneración.