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Homosynaptic frequency‐dependent depression by release site inactivation at neonatal hippocampal synapses in the stratum lacunosum‐moleculare
Author(s) -
Ma Rong,
Hanse Eric,
Gustafsson Bengt
Publication year - 2021
Publication title -
european journal of neuroscience
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.346
H-Index - 206
eISSN - 1460-9568
pISSN - 0953-816X
DOI - 10.1111/ejn.15357
Subject(s) - neuroscience , hippocampal formation , synaptic fatigue , stimulation , neurotransmission , kainate receptor , chemistry , interneuron , nmda receptor , biology , ampa receptor , inhibitory postsynaptic potential , receptor , excitatory postsynaptic potential , biochemistry
When activated at low frequencies (0.1–1 Hz), second postnatal week synapses onto the most distal part of the apical dendritic tree (stratum lacunosum‐moleculare) of rat hippocampal CA1 pyramidal cells display a frequency‐dependent synaptic depression not observed for the more proximal (stratum radiatum) synapses. Depression in this frequency range is thought of as a possible contributor to behavioural habituation. In fact, in contrast to the proximal synapses, the distal synapses provide more direct sensory information from the entorhinal cortex as well as from thalamic nuclei. The use of antagonists showed that the activation of GABA A , GABA B , NMDA, mGlu, kainate, adenosine, or endocannabinoid receptors was not directly involved in the depression, indicating it to be intrinsic to the synapses themselves. While the depression affected paired‐pulse plasticity in a manner indicating a decrease in vesicle release probability, the depression could not be explained by a stimulus‐dependent decrease in calcium influx. Despite affecting the synaptic response evoked by brief high‐frequency stimulation (10 impulses, 20 Hz) in a manner indicating vesicle depletion, the depression was unaffected by large variations in release probability. The depression was found not only to affect the synaptic transmission at low frequencies (0.1–1 Hz) but also to contribute to the depression evolving during brief high‐frequency stimulation (10 impulses, 20 Hz). We propose that a release‐independent process directly inactivating release sites with a fast onset (ms) and long duration (up to 20 s) underlies this synaptic depression.