C. Misra et al., Slow deactivation kinetics of NMDA receptors containing NR1 and NR2D subunits in rat cerebellar Purkinje cells, J PHYSL LON, 525(2), 2000, pp. 299-305
1. We have examined the deactivation kinetics of native Iv-methyl-D-asparta
te receptors (NMDARs) containing NR1 and NR2D subunits by patch-clamp recor
ding from Purkinje cells in cerebellar slices from young rats.
2. NMDAR-mediated whole-cell currents were elicited in response to bath app
lication of 20 mu M NMDA and 50 mu M glycine. The NMDAR-mediated currents w
ere small, with an average whole-cell conductance of approximately 750 pS.
3. Following the rapid application of brief pulses (1-10 ms) of 1 mM glutam
ate 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 agonis
t.
4. Analysis of individual channel openings revealed asymmetry of transition
s between the main- and subconductance states - a characteristic of NR1/NR2
D-containing NMDARs. The averaged macroscopic current exhibited a decay tim
e course which was well described by a single exponential function with a t
ime constant of similar to 3 s.
5. We conclude that native NR1/NR2D-containing NMDARs, like their recombina
nt counterparts, display very slow deactivation kinetics. This feature shou
ld provide a means for identification of these receptors at synapses, and i
ndicates that they do not contribute to the synaptic NMDAR currents so far
described.