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Synchronisation of neurotransmitter release during postnatal development in a calyceal presynaptic terminal of rat
Author(s) -
Chuhma Nao,
Koyano Konomi,
Ohmori Harunori
Publication year - 2001
Publication title -
the journal of physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.802
H-Index - 240
eISSN - 1469-7793
pISSN - 0022-3751
DOI - 10.1111/j.1469-7793.2001.0093m.x
Subject(s) - excitatory postsynaptic potential , trapezoid body , postsynaptic current , postsynaptic potential , neuroscience , neurotransmission , biophysics , neurotransmitter , chemistry , synapse , brainstem , biology , inhibitory postsynaptic potential , central nervous system , biochemistry , receptor
1 Mechanisms contributing to the synchronisation of transmitter release during development were studied in synapses of the medial nucleus of the trapezoid body (MNTB) using patch recording and Ca 2+ imaging techniques in a rat brainstem slice preparation. 2 Excitatory postsynaptic currents (EPSCs) were generated in an all‐or‐none manner at immature synapses (postnatal days earlier than P6). Many delayed miniature EPSC (mEPSC)‐like currents followed EPSCs at immature synapses, while observations of delayed mEPSC‐like currents were rare at mature synapses (later than P9). 3 At immature synapses bath application of either ω‐conotoxin GVIA or ω‐agatoxin‐IVA reduced EPSCs (both to 40% of control), and Ca 2+ currents in the presynaptic terminal (both to 70% of control). The frequency of delayed mEPSC‐like currents was reduced by ω‐conotoxin GVIA, but not by ω‐agatoxin IVA. 4 At immature synapses delayed mEPSC‐like currents were rare after incubation of the slice with extrinsic Ca 2+ buffers (EGTA AM). 5 At mature synapses many mEPSC‐like currents followed evoked EPSCs after partial block of Ca 2+ channels by bath application of a low concentration of Cd 2+ (3 μ m ) or ω‐agatoxin IVA (50 n m ) but not by low [Ca 2+ ] o (0.5‐1 m m ). 6 Ca 2+ transients induced by action potentials in presynaptic terminals were monitored by adding a high concentration of fura‐2 (200 μ m ) to the pipette. Their decay time course was slower at immature presynaptic terminals than at mature terminals. Both the Ca 2+ extrusion rate and the endogenous Ca 2+ binding capacity were estimated to be smaller at immature terminals than at mature terminals. 7 These results suggest that the maturation of synaptic transmission in MNTB progresses with the capacity for Ca 2+ clearance from the presynaptic terminal. The possible importance of developmental increases in both Ca 2+ clearance capacity and Ca 2+ currents is discussed in relation to the synchronisation of transmitter release.