Dynamics of dendritic calcium transients evoked by quantal release at excitatory hippocampal synapses

AUTOR(ES)

Murthy, Venkatesh N.

FONTE

The National Academy of Sciences

RESUMO

Synaptic N-methyl-d-aspartate (NMDA) receptors detect coincident pre- and postsynaptic activity and play a critical role in triggering changes in synaptic strength at central synapses. Despite intensive study of synaptic plasticity, relatively little is known about the magnitude and duration of calcium accumulation caused by unitary events at individual synapses. We used fluorescence imaging to detect NMDA receptor-mediated miniature synaptic calcium transients (MSCTs) caused by spontaneous release of synaptic vesicles in dendrites of cultured hippocampal neurons. MSCTs originated focally in dendritic regions <1 μm in length and decayed with a time constant of 0.35 ± 0.03 s. Multiple occurrences of MSCTs recorded at single sites had fluctuating amplitudes, with a coefficient of variation of 0.34. From the reduction in the spatial spread of MSCTs with decreasing concentration of indicator dye, we estimated that the dominant endogenous calcium buffer in dendrites is relatively immobile (diffusion coefficient between 10 and 50 μm2/s). We conclude that calcium rise caused by spontaneous quantal synaptic NMDA receptor activation (i) is variable, (ii) lasts for a time period briefer than previous measurements indicate, and (iii) is confined by endogenous calcium buffers to local dendritic regions even when synapses are not on spines.

Documentos Relacionados

• Presynaptic Calcium Dynamics and Transmitter Release Evoked by Single Action Potentials at Mammalian Central Synapses
• Sr2+ and quantal events at excitatory synapses between mouse hippocampal neurons in culture.
• Regulation of excitatory transmission at hippocampal synapses by calbindin D28k.
• The calcium dependence of spontaneous and evoked quantal release at the frog neuromuscular junction
• Paired-pulse depression of unitary quantal amplitude at single hippocampal synapses