Developmental regulation of the intracellular Ca2+ sensitivity of vesicle fusion and Ca2+–secretion coupling at the rat calyx of Held
AUTOR(ES)
Kochubey, Olexiy
FONTE
Blackwell Science Inc
RESUMO
Developmental refinement of synaptic transmission can occur via changes in several pre- and postsynaptic factors, but it has been unknown whether the intrinsic Ca2+ sensitivity of vesicle fusion in the nerve terminal can be regulated during development. Using the calyx of Held, a giant synapse in the auditory pathway, we studied the presynaptic mechanisms underlying the developmental regulation of Ca2+–secretion coupling, comparing a time period before, and shortly after the onset of hearing in rats. We found an ∼2-fold leftward shift in the relationship between EPSC amplitude and presynaptic Ca2+ current charge (QCa), indicating that brief presynaptic Ca2+ currents become significantly more efficient in driving release. Using a Ca2+ tail current protocol, we also found that the high cooperativity between EPSC amplitude and QCa was slightly reduced with development. In contrast, in presynaptic Ca2+ uncaging experiments, the intrinsic Ca2+ cooperativity of vesicle fusion was identical, and the intrinsic Ca2+ sensitivity was slightly reduced with development. This indicates that the significantly enhanced release efficiency of brief Ca2+ currents must be caused by a tighter co-localization of Ca2+ channels and readily releasable vesicles, but not by changes in the intrinsic properties of Ca2+-dependent release. Using the parameters of the intrinsic Ca2+ sensitivity measured at each developmental stage, we estimate that during a presynaptic action potential (AP), a given readily releasable vesicle experiences an about 1.3-fold higher ‘local’ intracellular Ca2+ concentration ([Ca2+]i) signal with development. Thus, the data indicate a tightening in the Ca2+ channel–vesicle co-localization during development, without a major change in the intrinsic Ca2+ sensitivity of vesicle fusion.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=2718258Documentos Relacionados
- Synaptic vesicle pool size, release probability and synaptic depression are sensitive to Ca2+ buffering capacity in the developing rat calyx of Held
- Activation of neurohypophysial vasopressin release by Ca2+ influx and intracellular Ca2+ accumulation in the rat.
- Ca2+ and Sr2+ entry induced Ca2+ release from the intracellular Ca2+ store in smooth muscle cells of rat portal vein.
- Role of Ca2+ channel in cardiac excitation-contraction coupling in the rat: evidence from Ca2+ transients and contraction.
- The effects of taurine on Ca2+ uptake by the sarcoplasmic reticulum and Ca2+ sensitivity of chemically skinned rat heart.