Slow deactivation kinetics of NMDA receptors containing NR1 and NR2D subunits in rat cerebellar Purkinje cells

• Published in: The Journal of physiology 2000-06, Vol.525 (2), p.299-305
• Main Authors: Misra, Charu, Brickley, Stephen G, Wyllie, David J A, Cull-Candy, Stuart G
• Format: Article
• Language: English
• Subjects: Animals; Glutamic Acid - pharmacology; In Vitro Techniques; Kinetics; Patch-Clamp Techniques; Purkinje Cells - drug effects; Purkinje Cells - metabolism; Rapid Report; Rats; Rats, Sprague-Dawley; Receptors, N-Methyl-D-Aspartate - antagonists & inhibitors; Receptors, N-Methyl-D-Aspartate - chemistry; Receptors, N-Methyl-D-Aspartate - metabolism
• ISSN: 0022-3751; 1469-7793
• DOI: 10.1111/j.1469-7793.2000.t01-1-00299.x

We have examined the deactivation kinetics of native N -methyl-D-aspartate receptors (NMDARs) containing NR1 and NR2D subunits by patch-clamp recording from Purkinje cells in cerebellar slices from young rats. NMDAR-mediated whole-cell currents were elicited in response to bath application of 20 μ m NMDA and 50 μ m glycine. The NMDAR-mediated currents were small, with an average whole-cell conductance of approximately 750 pS. Following the rapid application of brief pulses (1–10 ms) of 1 mM glutamate to outside-out membrane patches, we observed a low-conductance type of single-channel activity which lasted up to 30 s after the removal of agonist. Analysis of individual channel openings revealed asymmetry of transitions between the main- and subconductance states – a characteristic of NR1/NR2D-containing NMDARs. The averaged macroscopic current exhibited a decay time course which was well described by a single exponential function with a time constant of ∼3 s. We conclude that native NR1/NR2D-containing NMDARs, like their recombinant counterparts, display very slow deactivation kinetics. This feature should provide a means for identification of these receptors at synapses, and indicates that they do not contribute to the synaptic NMDAR currents so far described.