Synaptic vesicle pool size, release probability and synaptic depression are sensitive to Ca2+ buffering capacity in the developing rat calyx of Held
Braz. j. med. biol. res
;
42(1): 94-104, Jan. 2009. ilus, tab, graf
Article
Dans Anglais
| LILACS
| ID: lil-505422
ABSTRACT
The calyx of Held, a specialized synaptic terminal in the medial nucleus of the trapezoid body, undergoes a series of changes during postnatal development that prepares this synapse for reliable high frequency firing. These changes reduce short-term synaptic depression during tetanic stimulation and thereby prevent action potential failures during a stimulus train. We measured presynaptic membrane capacitance changes in calyces from young postnatal day 5-7 (p5-7) or older (p10-12) rat pups to examine the effect of calcium buffer capacity on vesicle pool size and the efficiency of exocytosis. Vesicle pool size was sensitive to the choice and concentration of exogenous Ca2+ buffer, and this sensitivity was much stronger in younger animals. Pool size and exocytosis efficiency in p5-7 calyces were depressed by 0.2 mM EGTA to a greater extent than with 0.05 mM BAPTA, even though BAPTA is a 100-fold faster Ca2+ buffer. However, this was not the case for p10-12 calyces. With 5 mM EGTA, exocytosis efficiency was reduced to a much larger extent in young calyces compared to older calyces. Depression of exocytosis using pairs of 10-ms depolarizations was reduced by 0.2 mM EGTA compared to 0.05 mM BAPTA to a similar extent in both age groups. These results indicate a developmentally regulated heterogeneity in the sensitivity of different vesicle pools to Ca2+ buffer capacity. We propose that, during development, a population of vesicles that are tightly coupled to Ca2+ channels expands at the expense of vesicles more distant from Ca2+ channels.
Texte intégral:
Disponible
Indice:
LILAS (Amériques)
Sujet Principal:
Vésicules synaptiques
/
Tronc cérébral
/
Calcium
/
Transmission synaptique
/
Signalisation calcique
Type d'étude:
Etude diagnostique
Limites du sujet:
Animaux
langue:
Anglais
Texte intégral:
Braz. j. med. biol. res
Thème du journal:
Biologie
/
Médicament
Année:
2009
Type:
Article
/
Congrès et conférence
Pays d'affiliation:
Brésil
/
États-Unis d'Amérique
Institution/Pays d'affiliation:
Oregon Health and Science University/US
/
Universidade de São Paulo/BR
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