NMDA Receptor-Mediated Currents in Rat Cerebellar Granule and Unipolar Brush Cells

Abstract

verse Slater. NMDA receptor-mediated currents in rat cerebellar granule and unipolar brush cells. J Neurophysiol 87: 1948 -1959, 2002; 10.1152/jn.00599.2001. The properties of N-methyl-D-aspartate (NMDA) receptor-mediated currents at the giant cerebellar mossyfiber unipolar brush cell (UBC) synapse were compared with those of adjacent granule cells using patch-clamp recording methods in thin slices of rat cerebellar nodulus. In UBCs, NMDA receptor-mediated excitatory postsynaptic currents (EPSCs) decayed as a single exponential whose time constant was independent of membrane potential. The EPSC was reduced in all cells by the NR1/NR2B-selective antagonist ifenprodil, and the Zn 2ϩ chelator N,N,NЈ,NЈ-tetrakis(2-pyridylmethyl)ethylenediamine (TPEN) produced a transient potentiation in 50% of cells. In contrast, the NMDA EPSC in granule cells decayed as a double exponential that dramatically switched to a slower rate at positive membrane potentials. The synaptic response in some granule cells also displayed a late second peak at positive potentials, and in others, activation of mossy fibers produced repetitive trains of EPSCs indicating they may be postsynaptic to the UBC network. Single-channel recordings of outside-out somatic patches from UBCs in magnesium-free solution revealed only high-conductance (50 pS) channels whose open time was increased with depolarization, but the opening frequency was decreased to yield a low (p o ϭ 0.0298), voltage-independent opening probability. Lowering extracellular calcium (2.5-0.25 mM) had no effects on channel gating, although an increase of single-channel conductance was observed at lower calcium concentrations. Taken together, the data support the notion that the NMDA receptor in UBCs may comprise both NR1/ NR2A and NR1/NR2B receptors. Furthermore, the properties of the EPSC in these two classes of feedforward glutamatergic interneurons display fundamental differences that may relate to their roles in synaptic integration.

Functional plasticity of the N-methyl-d-aspartate receptor in differentiating human erythroid precursor cells

“…The low conductance and slow deactivation time we have observed for NMDARs in polychromatic erythroblasts were shown to be characteristic for the receptor formed by the GluN2C/D and GluN3B subunits (49). Currents mediated by the NMDAR in proerythroblasts showed no plateau phase as it was reported for the NMDAR currents in neuronal cells (4). These findings indicate that an atypical subunit composition and functional pattern of NMDAR in erythroid cells resemble the properties of the receptors described for other nonneuronal tissues (7, 28, 39).…”

ON and OFF Unipolar Brush Cells Transform Multisensory Inputs to the Auditory System

“…However, the initial studies of mossy fiber-UBC synaptic transmission (Rossi et al, 1995; Kinney et al, 1997; Billups et al, 2002) were done prior to subtype characterization, and only the ON UBC was described. Since then, one other study of cerebellar UBCs investigated synaptic kinetics, again only describing ON UBCs (van Dorp and de Zeeuw, 2014).…”

Calcium-binding proteins in the cerebellar cortex of the bottlenose dolphin and harbour porpoise

“…As is known, cable properties of a dendritic arborization are largely determined by its geometry and span (Vetter et al, 2001). In particular, short and thick dendrites guarantee stable and efficient spike propagation to the soma, while a high spatial density of terminal arborization together with a long primary dendrite (as in the case of long-dendrite UBCs) impedes spike spatial summation and propagation (Kinney et al, 1997;Billups et al, 2002). Given the above, elaborated terminal arborization of dolphin UBCs suggests their high integrative capacities, and variation in primary dendrite length between potential UBC types may reflect differences in their cable properties.…”