Mc. Bellingham et al., DEVELOPMENTAL-CHANGES IN EPSC QUANTAL SIZE AND QUANTAL CONTENT AT A CENTRAL GLUTAMATERGIC SYNAPSE IN RAT, Journal of physiology, 511(3), 1998, pp. 861-869
1. Developmental changes in amplitude and time course of single-fibre-
evoked and spontaneous EPSCs mediated by AMPA and NMDA receptors at th
e endbulb-bushy cell synapse of rats from 4 to 22 days of age were rec
orded using whole-cell patch-clamp methods in in vitro slices of cochl
ear nucleus. 2. The mean conductance of the AMPA component of evoked E
PSCs increased by 68%, while that of the NMDA component decreased by 6
1%, for 12- to 18-day-old rats cf. 4- to 11-day old rats. 3. The mean
AMPA spontaneous EPSC conductance increased by 54%, while mean NMDA sp
ontaneous EPSC conductance decreased by 83%, for 12- to 22-day-old rat
s cf. 4- to 11-day-old rats. The mean number of quanta contributing to
peak evoked AMPA conductance also increased by 78% in the older age g
roup, after correction for the asynchrony of evoked quantal release. 4
. The decay time constant of spontaneous AMPA EPSCs showed a small dec
rease in older animals, while the decay time constant of spontaneous N
MDA EPSCs was markedly decreased in older animals. The decay time cons
tants of evoked NMDA EPSCs showed a quantitatively similar decrease to
that of spontaneous NMDA EPSCs. This suggests that AMPA receptor subu
nit composition is unlikely to undergo developmental change, while NMD
A receptor subunit composition may be substantially altered during syn
aptic maturation. 5. These data are consistent with a developmentally
increased efficacy of AMPA receptor-mediated synaptic transmission at
the endbulb-bushy cell synapse, due to an increase in underlying AMPA-
mediated quantal size and content during the same period as a transien
t co-localization of NMDA receptors.