Increased exocytotic capability of rat cerebellar granule neurons cultured under depolarizing conditions.
To obtain insights into the mechanisms underlying activity-dependent survival of neurons, we surveyed various indices of cellular activity in rat cerebellar granule neurons cultured under conditions advantageous and disadvantageous for survival. Previously, we reported that the turnover of Ca2+ (both influx and efflux) is activated in raised K+-cultures (survival condition), although the cytoplasmic Ca2+ concentration is not affected. We also reported that endocytotic activity was high in the high K+-cultures. In the present study, we used the release of FM1-43 dye [N-(3-triethylammoniumpropyl)-4-(4-dibutylamino)styryl)py ridium bromide] to determine the exocytotic capabilities of neurons cultured in normal K+ (death condition), high K+ (survival condition) and brain-derived neurotrophic factor-supplemented (survival condition) media. The FM1-43 releases triggered by K+-induced depolarization and glutamate exposure were significantly higher in the high K+-cultures than in normal K+-cultures. Interestingly, the neurons whose survival was supported by brain-derived neurotrophic factor did not show high exocytotic capability, indicating that the high exocytotic capability is not a mere result of viability. However, the number of synaptic sites per cell (as monitored by synaptophysin immunopositivity) was unaffected by culture conditions. The present results suggest that an enhanced exocytotic activity supported by a strengthened exocytotic capability may underlie the high viability of rat cerebellar granule neurons cultured under depolarizing conditions.
Yamagishi
S
S
Department of Biology, Osaka University Graduate School of Science, Toyonaka, Japan.
Fujikawa
N
N
Kohara
K
K
Tominaga-Yoshino
K
K
Ogura
A
A
D000818:Animals; D019208:Brain-Derived Neurotrophic Factor / Q000494:pharmacology; D002470:Cell Survival / Q000187:drug effects / Q000502:physiology; D002478:Cells, Cultured; D002531:Cerebellum / Q000166:cytology*; D005089:Exocytosis / Q000187:drug effects / Q000502:physiology*; D005260:Female; D005456:Fluorescent Dyes; D066298:In Vitro Techniques; D008297:Male; D008564:Membrane Potentials / Q000502:physiology; D009474:Neurons / Q000166:cytology* / Q000187:drug effects / Q000502:physiology*; D011189:Potassium Chloride / Q000494:pharmacology; D011726:Pyridinium Compounds; D000644:Quaternary Ammonium Compounds; D051381:Rats; D017208:Rats, Wistar; D013569:Synapses / Q000502:physiology
D019208:Brain-Derived Neurotrophic Factor; C073804:FM1 43; D005456:Fluorescent Dyes; D011726:Pyridinium Compounds; D000644:Quaternary Ammonium Compounds; D011189:Potassium Chloride