Relationship between the calcium release and the cerebellar LTD

Abstract

Long-term depression (LTD) of the parallel fiber (PF)–Purkinje cell (PC) synapse is an underlying mechanism by which motor coordination and learning are regulated. Elevation of cytoplasmic calcium in the PC dendrites is a critical event for LTD induction. To investigate the relationship between the calcium signal pattern and the LTD induction, we performed calcium imaging from PCs in acute cerebellar slices. LTD was induced by ten trains of 50Hz x 5 bursts of parallel fiber stimuli at 1Hz in PCs from 2 weeks old mice, but not from 4 weeks old mice. This PF short burst stimuli (50Hz x 5) produced a biphasic calcium transient in dendrites of PCs, first peak of which reflects calcium influx and second one does calcium release from intracellular calcium stores. By comparing amplitudes of the first and second calcium transients, we found a correlation between calcium release activity and LTD amplitude in PCs from 2 weeks old mice. This finding unveils an importance of calcium release especially in synaptic maturation in the developing cerebellar cortex. [Jpn J Physiol 55 Suppl:S149 (2005)]