Development of electrophysiological properties of intracerebellar nuclei neurones in rat cerebellar slices maintained in vitro

140 HIGH EXTRACELLULAR K + PROMOTES THE SURVIVAL OF CEREBELLAR GRANULE CELLS IN CULTURE ~+ THROUGH A Ca -DEPENDENT MECHANISM. V i t t o r i o Ga l lo , Ann E. Kingsbury and Robert Balazs, MRC Developmental Neurobiology Uni t , 33 John's Mews WCIN 2NS London, U.K. Granule ce l l s from P8 ra t cerebe l la can be cul tured fo r 2 weeks in a serum-supplemented medium conta in ing 25mM K +, but d ie a f t e r 5-6 days in v i t r o (DIV) i~ less than 15mM K +. Cel ls grown fo r the f i r s t 3 days in 5mM and then sh i f ted to 25mM K surv ive fo r 2 weeks and are morpho log ica l ly i nd i s t i ngu ishab le from ce l l s cu l tured in 25mM K + from 0 DIV,but when cu l tures are sh i f ted from 25mM to 12mM K ÷ a l l neurones d ie w i th in 48 hours. At 5 DIV vera t r ineinduced te t rodo tox in (TTX)-sensi t ive Glu release is s im i la r in cul tures grown in 5mM or 25mM K + and other indices of neuronal maturat ion are also comparable. In terms of ce l l surv iva l high K + + can be replaced by Rb , but not by ve ra t r i ne ( I 5 # g /ml ) . The e f f ec t of high K + on ce l l surv iva l is not counteracted by growing ce l l s in the presence of TTX (I #M) or ~ l o c a i n e (50#g /m l ) . Neurones cul tured in a 25mM K + medium conta in ing e i t he r lOmM Mg ~ , 1,6 mM EGTA or IO~M D600 survive only fo r 5-6 DIV. The vol tage dependent component of qbcaZ+ uptake, manifested in these cul tures a f t e r 5 DIV, increases rap id l y reaching a "p lateau" by 8DIV. A f te r 3DIV high K + is necessary