Post-tetanic potentiation involves the presynaptic binding of calcium to calmodulin

Hippocampal Excitatory Synaptic Transmission and Plasticity Are Differentially Altered during Postnatal Development by Loss of the X-Linked Intellectual Disability Protein Oligophrenin-1

Oligophrenin-1 (OPHN1) is a Rho-GTPase-activating protein (RhoGAP), whose mutations are associated with X-linked intellectual disability (XLID). OPHN1 is enriched at the synapse in both pre- and postsynaptic compartments, where it regulates the RhoA/ROCK/MLC2 signaling pathway, playing a critical role in cytoskeleton remodeling and vesicle recycling. Ophn1 knockout (KO) adult mice display some behavioral deficits in multiple tasks, reminiscent of some symptoms in the human pathology. We also previously reported a reduction in dendritic spine density in the adult hippocampus of KO mice. Yet the nature of the deficits occurring in these mice during postnatal development remains elusive. Here, we show that juvenile KO mice present normal basal synaptic transmission, but altered synaptic plasticity, with a selective impairment in long-term depression, but no change in long-term potentiation. This contrasts with the functional deficits that these mice display at the adult stage, as we found that both basal synaptic transmission and long-term potentiation are reduced at later stages, due to presynaptic alterations. In addition, the number of excitatory synapses in adult is increased, suggesting some unsuccessful compensation. Altogether, these results suggest that OPHN1 function at synapses is differentially affected during maturation of the brain, which provides some therapeutic opportunities for early intervention.

Influence of tetanic stimulation on the staircase phenomenon and the acceleromyographic time-course of neuromuscular block: a randomized controlled trial

During neuromuscular monitoring, repeated electrical stimulation evokes muscle responses of increasing magnitude ('staircase phenomenon', SP). We aimed to evaluate whether SP affects time course and twitches' values of an acceleromyographic assessed neuromuscular block with or without previous tetanic stimulation. Fifty adult patients were randomized to receive a 50 Hz tetanic stimulus (S group) or not (C group) before monitor calibration. After 20 min of TOF ratio (TOFr) stimulation rocuronium was administered. Onset time of block (primary endpoint), recovery of T1 to 25%, TOFr to 0.9, and recovery index were compared. We also compared T1 and TOFr at baseline, post-stimulation, and during recovery from block. Moreover the correlation between T1 at maximum recovery and (a) baseline T1 and (b) post-stimulation T1 along with T1/TOFr ratio during recovery were evaluated. After stimulation median T1 increased (32%) in group C and decreased (16%) in group S (P = 0.0001). Onset time (Median [IQR] in seconds) was 90 (29-77) vs. 75 (28-60) in C and S group (P = 0.002). Time [Mean (SD) in minutes] to normalized TOFr 0.9 were 70.13 (14.9) vs. 62.1 (21.2) in C and S groups (P = 0.204). TOFr showed no differences between groups at any time point. T1 at maximum recovery showed a stronger correlation with post-stabilization T1 compared to baseline. (ρ = 0.80 and ρ = 0.85, for C and S groups.) Standard calibration does not ensure twitch baseline stabilization and prolongs onset time of neuromuscular block. TOF ratio is not influenced by SP.

Copper Inhibits NMDA Receptor-Independent LTP and Modulates the Paired-Pulse Ratio after LTP in Mouse Hippocampal Slices

Copper misregulation has been implicated in the pathological processes underlying deterioration of learning and memory in Alzheimer's disease and other neurodegenerative disorders. Supporting this, inhibition of long-term potentiation (LTP) by copper (II) has been well established, but the exact mechanism is poorly characterized. It is thought that an interaction between copper and postsynaptic NMDA receptors is a major part of the mechanism; however, in this study, we found that copper (II) inhibited NMDA receptor-independent LTP in the CA3 region of hippocampal slices. In addition, in the CA3 and CA1 regions, copper modulated the paired-pulse ratio (PPR) in an LTP-dependent manner. Combined, this suggests the involvement of a presynaptic mechanism in the modulation of synaptic plasticity by copper. Inhibition of the copper-dependent changes in the PPR with cyclothiazide suggested that this may involve an interaction with the presynaptic AMPA receptors that regulate neurotransmitter release.