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At least 1,405 records · Page 78Linked to original sources
PubMed2003

Pathway-specific differences in subunit composition of synaptic NMDA receptors on pyramidal neurons in neocortex.

Heterogeneity of synaptic inputs onto neocortical layer 5 pyramidal neurons could result from differences in the underlying receptors, yet previous work has shown that functional attributes of AMPA receptors are uniform among synaptic connections onto these neurons. To determine whether NMDA receptors (NMDARs) would be similarly uniform, we compared in the same pyramidal neurons pharmacologically isolated NMDAR-mediated EPSCs evoked by stimulation of two anatomically distinguishable pathways, callosal or intracortical. Based on differences in voltage dependence, decay kinetics, apparent Mg2+sensitivity, and subunit-specific (NR2A, NR2B, and NR2C/D) pharmacology, we found NMDARs at these inputs to be distinct. Furthermore, NMDARs activated by the intracortical pathway were more efficient at integrating EPSPs and bringing the neuron closer to the spike-firing threshold than the callosal pathway. These results suggest that pyramidal neurons encode information differentially depending on the origin of their neocortical inputs and that NMDAR-dependent synaptic plasticity may be pathway specific.

Action Potentials↗
PubMed2005

Heterogeneity of axon terminals expressing VGLUT1 in the cerebral neocortex.

Using immunocytochemical techniques and confocal microscopy we have studied the localization of the vesicular glutamate transporters (VGLUTs) 1 and 2 in the mammalian cerebral cortex. The cardinal observations gathered to date can be summarized as follows: 1) Many VGLUT1-positive puncta coexpressing synaptophysin-1 outline pyramidal cell somata and proximal dendrites; of these, a sizeable fraction coexpress VGAT, the vesicular transporter for GABA; 2) VGLUT2-positive puncta are also present in layers II-III and some of them coexpress VGLUTI. These findings suggest that in the cerebral cortex of adult rats axon terminals expressing VGLUT1 are heterogeneous.

Amino Acid Transport Systems↗
PubMed2005

[Synaptic plasticity of neocortex of albino rats in diffuse-focal injuries of the brain].

In an experiment conducted using mature albino rats, the regularities of reorganization of synaptic architectonics of cortical layer I of the brain were studied in the areas of diffuse-focal injuries. The models of acute break of systemic circulation (clinical death) as a result of 6-minute-long mechanical asphyxia, compression of common carotid arteries for 20 min (ischemia) and rotatory sublethal injury according to Noble-Collip method (cranial trauma), were used. Using the methods of electron microscopy and morphometric analysis, it was shown that a reduction in a general numerical density of synapses was accompanied by the changes in relative and absolute numbers of major variants of synaptic organization. The content of large simple and perforated contacts was increased, as well as of synapses with invaginated synaptic membranes, containing mitochonria and spine apparatus. The changes detected are considered as a structural basis for realization of the mechanisms of synaptic plasticity in diffuse-focal injuries of the brain.

Animals↗
PubMed2006

[Intranasal epitalon infusion modulates neuronal activity in the rat neocortex].

Properties of tetrapeptide epitalon (Ala-Glu-Asp-Gly) constructed on the basis of pineal peptide extract, have been studied. The intranasal infusions: a noninvasive way to deliver this peptide to CNS hypassing the blood-brain barrier, was used. The aim of the study is to estimate epitalon action on rat motor cortex spontaneous activity. Wistar male rats were anesthetized with urethane (1 g/kg). Extracellular unit recording was made using glass microelectrodes (1-2 MOhm). After recording of spontaneous activity (10-15 min), epitalon intranasal infusion (2 ng) was followed by 30-minute recording. Within a few minutes after the infusion, significant activation of neural activity was observed (2-2.5-fold higher frequency of neuronal spikes). Complex response consisting of several phases was identified in some recordings. The spikes frequency growth during 5 to 7 min (first phase) after the infusion was followed by the second (11-12 min) and the third (17-18 min) phases. An increase of neuronal spontaneous activity was conditioned by the higher frequency of already active units and by the involvement of previously silent cells. At least the first phase of epitalon action can be explained by direct action of the peptide on the cells of the motor cortex.

Action Potentials↗