Acute and chronic changes in K(+)-induced depolarization alter NMDA and nNOS gene expression in cultured cerebellar granule cells.
The influence of low or high (10 or 25 mM) K(+)-induced membrane depolarization on the mRNA levels for NMDA receptor subunits was investigated by RNase protection assay in cultured rat cerebellar granule cells. Cells, maintained for 7 days in K25+, a condition that promotes their survival and maturation, express the highest levels of NR-1 and NR-2A mRNA, whereas NR-2B is maximally expressed in cells grown in K10+. Acute changes in medium K+ concentration had a significant effect on the mRNA levels for NMDA receptor subunits. A concomitant reduction of NR-2A mRNA and induction of NR-2B was observed following a 24-h shift of the culture medium from K25+ to K10+. Under these circumstances NR-2C, not detected in basal conditions, became expressed. Neuronal nitric oxide synthase, an enzyme linked to NMDA receptor activation, was also influenced by growth conditions. Its expression, higher under low excitation (K10+), is induced in the shift from K25+ to K10+ and is markedly decreased in the opposite situation. These data indicate that several factors may influence the expression of NMDA receptor subunits and consequently may modulate the function of this receptor complex and its adaptation to acute and chronic changes in neuronal activity.
Tascedda
F
F
Center of Neuropharmacology, Institute of Pharmacological Sciences, University of Milan, Italy.
Molteni
R
R
Racagni
G
G
Riva
M A
MA
D000818:Animals; D000831:Animals, Newborn; D002478:Cells, Cultured; D002531:Cerebellum / Q000502:physiology*; D003470:Culture Media; D007527:Isoenzymes / Q000096:biosynthesis; D046911:Macromolecular Substances; D008564:Membrane Potentials / Q000187:drug effects; D009474:Neurons / Q000166:cytology / Q000378:metabolism / Q000502:physiology*; D019001:Nitric Oxide Synthase / Q000096:biosynthesis*; D011188:Potassium / Q000494:pharmacology*; D012333:RNA, Messenger / Q000096:biosynthesis; D051381:Rats; D017207:Rats, Sprague-Dawley; D016194:Receptors, N-Methyl-D-Aspartate / Q000096:biosynthesis*; D014158:Transcription, Genetic / Q000187:drug effects
D003470:Culture Media; D007527:Isoenzymes; D046911:Macromolecular Substances; D012333:RNA, Messenger; D016194:Receptors, N-Methyl-D-Aspartate; D019001:Nitric Oxide Synthase; D011188:Potassium