M. Yuzaki et al., FUNCTIONAL NMDA RECEPTORS ARE TRANSIENTLY ACTIVE AND SUPPORT THE SURVIVAL OF PURKINJE-CELLS IN CULTURE, The Journal of neuroscience, 16(15), 1996, pp. 4651-4661
Conflicting evidence exists concerning the activity of NMDA receptors
(NMDARs) in cerebellar Purkinje cells and their possible functions. To
investigate the activity of NMDARs, we used whole-cell recording on i
mmunocytochemically identified Purkinje cells in primary culture. In a
ddition, we used mice with a disrupted NMDAR1 gene that lack functiona
l NMDARs (NR1-/-) to assess the physiological role of NMDARs. In cultu
res from normal mice, NMDA-mediated currents were detected in all iden
tified Purkinje cells at 4 d in vitro (div). After 14 d, however, NMDA
responses were reduced in amplitude, whereas the responses to kainate
and glutamate increased steadily in amplitude. In addition, the NMDA-
induced current displayed a pronounced desensitization at these later
stages; peak current declined to zero during steady application of NMD
A. At 7 div, the number of surviving Purkinje cells was less in cultur
es treated with NMDA antagonists, and their survival was dose-dependen
t. Purkinje cell survival was correspondingly poorer in cultures from
the NR1-/- mice than in wild-type controls, suggesting that NMDAR acti
vity enhances the survival of Purkinje cells in vitro. The addition of
moderate doses of NMDA promoted the survival of wild-type Purkinje ce
lls in the presence of tetrodotoxin. Feeder layers of cerebellar granu
le cells derived from wild-type or NR1-/- mice promoted survival of Pu
rkinje cells to a similar degree, suggesting that the NMDAR in Purkinj
e cells, but not in other cells, is directly involved in Purkinje cell
viability. The results demonstrate that NMDARs transiently produce me
mbrane current in Purkinje cells and may serve as one of the epigeneti
c factors that support the survival of Purkinje cells in vitro.