DOI: 10.5061/dryad.rxwdbrvh4
title: Adiponectin rescues synaptic plasticity in the dentate gyrus of a mouse model of fragile X syndrome

description: Fragile X Syndrome (FXS) is the most common inherited cause of
 intellectual disability and is the leading known single-gene cause of
 autism spectrum disorder. FXS patients display varied behavioural deficits
 that include mild to severe cognitive impairments in addition to mood
 disorders. Currently, there is no cure for this condition, however, there
 is an emerging focus on therapies that inhibit mTOR-dependent protein
 synthesis due to the clinical effectiveness of metformin for alleviating
 some behavioural symptoms in FXS. Adiponectin (APN) is a neurohormone that
 is released by adipocytes and provides an alternative means to inhibit
 mTOR activation in the brain. In these studies, we show that Fmr1 KO mice,
 like FXS patients, show reduced levels of circulating APN, and that both
 LTP and LTD in the DG (dentate gyrus) are impaired. Brief (20 min)
 incubation of hippocampal slices in APN (50 nM) was able to rescue both
 LTP and LTD in the DG and increased both the surface expression and
 phosphorylation of GluA1 receptors. These results provide evidence for
 reduced adiponectin levels in FXS playing a role in decreasing
 bidirectional synaptic plasticity and show that therapies that enhance
 adiponectin levels may have therapeutic potential for this and related
 conditions.
description: Slices were perfused with ACSF (30 °C) at a rate of approximately
 2 ml/min and field excitatory postsynaptic potentials (fEPSPs) recorded
 using an Axon MultiClamp 700B amplifier connected to a PC running Clampex
 10.2 software (Molecular Devices, CA, USA). An upright Olympus BX50WI
 microscope was used to assist with visually placing stimulating and
 recording electrodes in the middle of the molecular lay of the DG as
 previously described. fEPSPs were elicited by delivering a 120 μs (10–40
 μA) current pulse every 15s to the medial perforant path (MPP) via a
 concentric bipolar stimulating electrode (FHC, Bowdoin, ME). A
 borosilicate glass recording electrode (1 MΩ) was filled with ACSF and
 visually placed about 200 μm from the stimulating electrode. A stable
 baseline was recorded for at least 15 min using a stimulation magnitude
 that elicit a response of 50% of the maximum amplitude obtained for
 synaptic potentiation, and 70% for synaptic depression experiments.
 Following this, a paired-pulse protocol and an input-output (I/O)
 protocols were applied to evaluate possible changes in synaptic
 transmission induced by the experimental variables investigated.
 Paired-pulse experiments consisted in the application of 6 sets of 2
 pulses each with a 50 ms interpulse interval, and a ratio was calculated
 by dividing the slope of the second fEPSP by the first.
 In order to induce LTP induction in the DG, slices were exposed
 to the GABA<sub>A</sub> receptor antagonist bicuculline
 methiodide during baseline recordings (5 μM washed for 20 min;
 Sigma-Aldrich, ON, Canada). This protocol allows for a significant
 reduction in tonic inhibition and isolation of the excitatory component of
 synaptic transmission in this hippocampal subregion. In addition, to
 assess the impact of long-term exposure to APN (50 nM; &gt;90 min
 incubation), slices were constantly exposed to ACSF supplemented with this
 hormone during both recovery time and recordings. Short-time exposure (50
 nM; 20 min incubation) was evaluated by exposing slices to APN diluted in
 ACSF for 20 min during baseline recordings (in addition to bicuculline
 methiodide for LTP experiments). LTP was induced by applying a
 high-frequency stimulus (HFS; 4 trains of 50 pulses at 100 Hz, 30 s
 apart), and LTD by prolonged low-frequency stimulation (LFS; 900 pulses at
 1 Hz, 1 s apart). Responses were recorded for 60 min after the
 conditioning stimulus, and fEPSPs slopes were calculated using Clampfit 10
 (Axon Instruments). Two parameters were then quantified for statistical
 comparisons: LTP was calculated ~60 min following induction by averaging
 20 successive recordings; PTP (post-tetanic potentiation) was calculated
 by averaging the first 4 responses following induction. (This measure
 includes a mixture of a rapid NMDAR-independent potentiation and
 NMDAR-dependent short-term potentiation; STP). Experiments were conducted
 using hippocampal slices that exhibited response amplitudes exceeding 1 mV
 and a favorable fEPSP to fiber volley ratio of 2:1 or higher, which was
 considered qualitative indicators of robust tissue responses.
description: # Adiponectin rescues synaptic plasticity in the dentate gyrus of a mouse
 model of fragile X syndrome
 [https://doi.org/10.5061/dryad.rxwdbrvh4](https://doi.org/10.5061/dryad.rxwdbrvh4) ## Description of the data and file structure An excel spreadsheet is provided that consists of 4 sheets. The first presents the individual slice data from each animal in a series of columns. Columns are grouped according to experimental group. Page 1 is specific to LTP data, while Page 2 is specific to LTD data. On page 3, the input/output data for each slice is presented in a series of boxes/columns for each experimental group. On page 4, the paired-pulse data for each slice is presented in a series of boxes/columns for each experimental group. ## Sharing/Access information Additional information can be obtained by directly contacting the authors.  ## Code/Software All data was analyzed using PClamp software, with slope values exported into Excel. Statistical analyses were performed using GraphPad Prism9 (GraphPad Software, LLC).