CYCLOHEXIMIDE ABOLISHES PERTUSSIS TOXIN-INDUCED INCREASE IN GLUTAMATE RELEASE FROM CEREBELLAR GRANULE NEURONS

Release of glutamate from cerebellar granule neurones was stimulated either by adding 50 mM K+ to normal Krebs medium, or by adding 5 mM Ca2+ to neurones continuously depolarised with 50 mM KC in the absence of Ca2+. Pre-incubation of neurones for 16 h with pertussis toxin (PTX) increased the stimulated glutamate release in both K+-stimulated and continuously depolarised neurones. Under both conditions, the PTX-induced increase in release was abolished by cycloheximide. In contrast, in the presence of cycloheximide, PTX still prevented the GABA, agonist (-)-baclofen from inhibiting glutamate release. These results suggest that G-protein ADP-ribosylation by PTX in cerebellar granule neurones may increase synthesis of a protein associated with the L-type calcium channel.