Changes in synaptic strength and presynaptic release at the PP
synapses
Functionally, the glutamatergic inputs to the DG convey distinct types
of somatosensorial information. The MPP conveys spatial information from
the MEC, and the LPP transfers multisensorial information from the LEC
(Hunsaker et al., 2007; Fernández-Ruiz et al., 2021). Moreover, the
synaptic transfer is sustained by axons with unique electrophysiological
properties that determine plasticity capabilities and the pace and
strength of neurotransmitter release(Petersen et al., 2013;
Collitti-Klausnitzer et al., 2021). Those synaptic features have been
robustly demonstrated in this study. Consistent with previous works
(Segev et al., 2020; Márquez et al., 2023), our FV and PPF analyses
revealed that MK-801 alters the FV amplitude (or presynaptic action
potentials) and glutamate release. Dysregulation in the propagation of
the FV and the subsequent activation of the molecular machinery
underlying glutamate release may explain the reduced strength of the
glutamatergic transmission found in the MPP synapse. In line with this
possibility, transient hypofunction of NMDARs interferes with the
functional expression of presynaptic proteins that control
neurotransmitter release in animal models of schizophrenia (Maher and
LoTurco, 2012; Saggu et al., 2013) and schizophrenic individuals (Egbujo
et al., 2016). Finally, the altered neurotransmitter release process in
the MPP compared to the LPP synapse of MK-801-treated animals may
suggest a marked dysregulation in transferring spatial information but
not non-spatial information from the PP to the DG, a phenomenon that
requires additional investigation.