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High-voltage-activated Ca2+ currents show similar patterns of expression in stellate and pyramidal cells from rat entorhinal cortex layer II
No full textDifferential expression of resurgent sodium current in rat hippocampal, parahippocampal, and palaeocortical neurons.
No full textExpression of resurgent sodium current in pyramidal neurons of rat perirhinal cortex: evidence for axonal location of the underlying channels
No full textAnalysis of resurgent sodium-current expression in rat parahippocampal cortices and hippocampal formation.
No full textThree functionally different types of voltage-dependent Na currents in rat cerebellar granule cells in situ
No full textZn2+ modulates multiple types of neuronal voltage-gated Ca2+ channels at physiological Ca2+ levels
No full textEffects of Cu2+, Co2+, and Mn2+ on the gating kinetics of high-voltage-activated Ca2+ channels in rat palaeocortical neurons
No full textResurgent Na+ current in pyramidal neurones of rat perirhinal cortex: axonal location of channels and contribution to depolarizing drive during repetitive firing.
Full text linkThe perirhinal cortex (PRC) is a supra-modal cortical area that collects and integrates information originating from uni- and multi-modal neocortical regions and directed to the hippocampus. The mechanisms that underlie the specific excitable properties of the different PRC neuronal types are still largely unknown, and their elucidation may be important in understanding the integrative functions of PRC. In this study we investigated the expression and properties of resurgent Na+ current (INaR) in pyramidal neurones of rat PRC area 35 (layer II). Patch-clamp experiments in acute PRC slices were first carried out. A measurable INaR was expressed by a large majority of neurones (31 out of 35 cells). INaR appeared as an inward, slowly-decaying current elicited upon step repolarisation after depolarisations sufficient to induce nearly complete inactivation of the transient Na+ current (INaT). INaR had a peak amplitude of about 2.5% that of INaT, and showed the typical biophysical properties also observed in other neuronal types (i.e. cerebellar Purkinje and granule cells), including a bell-shaped current-voltage relationship with a peak at approximately –40 mV, and a characteristic acceleration of activation and decay speed at potentials negative to –45 mV. Current-clamp experiments were then carried out in which repetitive action-potential discharge at various frequencies was induced with depolarising current injection. The voltage signals thus obtained were then used as command waveforms for voltage-clamp recordings. These experiments showed that a Na+ current identifiable as INaR activates in the early interspike phase even at relatively high firing frequencies (20 Hz), thereby contributing to the depolarising drive and possibly enhancing repetitive discharge. In acutely dissociated area-35 layer-II neurones, as well as in nucleated patches from the same neurones, INaR was never observed, despite the presence of typical INaTs. Because in both preparations neuronal processes are lost, we carried out experiments of focal tetrodotoxin (TTx) application in slices to verify whether the channels responsible for INaR are located in compartment(s) different from the soma. We found that TTx preferentially inhibited INaR when applied close to the site of axon emergence from soma, whereas application to the apical pole of the soma had a significantly smaller effect on INaR. Our results indicate that in area-35 pyramidal cells INaR is largely generated in the axon initial segment, where it may participate to setting the coding properties of these neurones
The duration and amplitude of the plateau phase of ATP- and ADP-evoked Ca(2+) signals are modulated by ectonucleotidases in in situ endothelial cells of rat aorta
No full textCu2+, Co2+, and Mn2+ Modify the Gating Kinetics of High-Voltage-Activated Ca2+ Channels in Rat Palaeocortical Neurons
No full textAbstract. The effects of three divalent metal cations (Mn2+, Co2+, and Cu2+) on high-voltage-activated (HVA) Ca2+ currents were studied in acutely disso-ciated pyramidal neurons of rat piriform cortex using the patch-clamp technique. Cu2+, Mn2+, and Co2+ blocked HVA currents conducted by Ba2+ (IBa) with IC50 of 920 nM, 58 lM, and 65 lM, respec-tively. Additionally, after application of non-saturating concentrations of the three cations, resid-ual currents activated with substantially slower ki-netics than control IBa. As a consequence, the current fraction abolished by the blocking cations typically displayed, in its early phase, an unusually fast-decaying transient. The latter phenomenon turned out to be a subtraction artifact, since none of th
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