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Developmental increase of asynchronic glutamate release from hippocampal synapses in mutant taiep rat
Author(s) -
Fuenzalida Marco,
Aliaga Esteban,
Olivares Virginia,
Roncagliolo Manuel,
Bonansco Christian
Publication year - 2009
Publication title -
synapse
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.809
H-Index - 106
eISSN - 1098-2396
pISSN - 0887-4476
DOI - 10.1002/syn.20622
Subject(s) - synaptophysin , excitatory postsynaptic potential , neurotransmission , neuroscience , glutamate receptor , hippocampal formation , biology , neurotransmitter , cnqx , postsynaptic potential , inhibitory postsynaptic potential , stimulation , chemistry , medicine , ampa receptor , central nervous system , immunohistochemistry , receptor
During development, regulation of the strength of synaptic transmission plays a central role in the formation of mammalian brain circuitries. In taiep rat, a neurological mutant with severe reactive astrogliosis and demyelination, we have described alterations in the synaptic transmission in central neurons, characterized by asynchronous excitatory postsynaptic currents ( ASYN EPSCs), because of delayed neurotransmitter release. This hippocampal synaptic dysfunction has been described in juvenile mutants, concomitantly with the appearance of their main glial alterations. However, it is unknown whether this abnormal synaptic activity is correlated with some alterations of synaptic maturation during the postnatal development. Using intracellular electrophysiological recordings and immunohistochemistry assays, we studied the maturation of CA3‐CA1 synapses in taiep rats. In taiep , the number of ASYN EPSCs evoked by conventional stimulation of Schaffer collaterals increases with age (P7–P30) and can be evoked by stimulation of single fiber. The amplitude and frequency of spontaneous EPSC (sEPSC) increased during the postnatal development in both control and taiep rats. However, in taiep , the increase of sEPSC frequency was significantly higher than in the control rats. The frequency of miniature EPSC (mEPSC) increased over the studied age range, without differences between taiep and control rats. In both control and taiep groups, the synaptophysin immunostaining (SYP‐IR) in the stratum radiatum of CA1 region was significantly lower in the juvenile (P30) than in the neonatal (P10) rats, suggesting that synaptic pruning is normally occurring in taiep , even when SYP‐IR was higher in taiep than control in both ages studied. These results suggest that, in taiep mutants, the asynchronic transmission is due to a dysfunction in the glutamate release mechanisms that progressively increases during development, which is not attributable to the existence of aberrant synaptic contacts. Synapse 63:502–509, 2009. © 2009 Wiley‐Liss, Inc.