Synaptic Transmission - Science topic
The communication from a NEURON to a target (neuron, muscle, or secretory cell) across a SYNAPSE. In chemical synaptic transmission, the presynaptic neuron releases a NEUROTRANSMITTER that diffuses across the synaptic cleft and binds to specific synaptic receptors, activating them. The activated receptors modulate specific ion channels and/or second-messenger systems in the postsynaptic cell. In electrical synaptic transmission, electrical signals are communicated as an ionic current flow across ELECTRICAL SYNAPSES.
Questions related to Synaptic Transmission
I think both are used mainly for blocking GABAA receptors. Since gabazine is more selelctive for GABAA receptors, is it better to use for studying EPSC? Is it enough to block IPSC by only blocking GABAA receptors? Thanks.
Hello to everyone,
my name is Stylianos and these days I have focused on pairing recordings.
I cause 5 APs (5 pulses 20Hz) to a SOM-Martinotti neuron and I record IPSCs in a principal neuron in cortical slices at 0 mV in presence of DNQX and CGP. I found depression of the synaptic transmission (pulses 2,3,4,5 were smaller in amplitude compared to the 1st). This finding is in agreement with the literature.
BUT.....When I did the same experiment by optogenetically activating many SOMs with CAG.ChR2 and recording IPSCs in principal neurons, I found facilitation of the 2nd pulse compared to the 1st (in these experiments I applied the PPR protocol with 2 pulses at 20Hz).
So, I am wondering if there is an explanation about this discrepancy.
I thank you a priori for reading this.
I have noticed an increased in the asymmetrical synaptic excitatory junctions to be increased in the diabetic brain but could not find any discussion of this in the literature at present. If you have any information or publications regarding this question please share with me when you have the time.
My hypothesis is that in younger diabetic brains this increase in asymmetrical synaptic excitatory junctions may result in an overuse phenomenon and result in a later or older models in their attentuation and or loss as in accelerated aging in the diabetic brain. Thank you for your time and consideration.
M.R. (Pete) Hayden, MD
Two papers are using the method.
One attached and the other cited here: "Single rodent mesohabenular axons release glutamate and GABA" Root et al 2014
is this theory right?
Pathway 1: the fast increase of intercellular [K+] produced by the spiking activity of the postsynaptic neuron.
Pathway 2: the slow production of a mediator (Glutamat) triggered by the synaptic activity.
Neurons are grown on coverslips in culture after some time they form connections and synapses (very basic networks). What kind of stimulator (digitimer) do i get to look at synaptically stimulated APs? I have used a voltage stimulator like the DS2 (digitimer) with a bipolar electrode in brain slice neurons, but I'm not sure if that's the best kind of stimulation for neurons in culture. Is current stimulator better or biphasic and what difference does it make? Also what kind of electrode would work better? Would a bipolar electrode fry my neuron cultures?
If one uses antibodies against VGLUT1 and synaptophysin to stain in WT cultured hippocampal neurons, one expects the immunosignals to co-localize, since both are synaptic vesicle specific proteins. how to explain the finding of solely vglut1 signals? I understand if I have only synaptophysin signals, maybe I thereby detected vgat expressing neurons, but synaptic vesicles that are positive for vglut1 and not stained with anti synaptophysin antibody?
I’m doing in vivo electrophysiology in anesthetized mice where I record evoked field excitatory post synaptic potentials (fEPSP) in the hippocampus (electrical stimulation at CA 3 fibers; recording at CA1 stratum radiatum). I would like to learn more strategies to study short-term plasticity mechanisms and other parameters of basal synaptic function in in vivo anesthetized preparation, always keeping in mind that intend to study evoked fEPSP. So far I use classical input/output measurements and Paired Pulse analysis but I’ve seen other types of protocols although I’m not yet familiar with the principles behind. If someone has any suggestion/advice, I would be very grateful. Thank you.
In our scenario, we let an Axon grow in Vitro over a distance of 500µm before it will find Dendrites to connect to.
How many Synapses are formed by that Axon when coming in contact with those Dendrites?
- The elapsed time will be 7 Days
- The Cells are embryonic Hippocampal cells from Rats
A second Question would be related: What would be the spatial spreading of the most distant Synapses?
I need to know this to solve a problem we have when connecting single Neurons to Clusters.
I'm a little bit in trouble with LTP on CA1. I performed some experiments inducing LTP after HFS (1 for 100 stimuli at 250Hz). This protocol is able to induce a strong potentiation of the synapse. My problem is that the potentiation after the induction is not stable and the response continues to increase without reaching a plateau. What do you think the problem is? I recorded extracellularly fEPSPs from hippocampal brain slices (400uM thickness; flow rate of about 2 mL/minute).
Thanks in advance for your advices.
It is quite well established that DHPG perfused in acute hippocampal slices causes a transient decrease in synaptic transmission in hippocampal CA1 region (DHPG 100 micoM is perfused for 10 minutes in Palmer et al. 1997) but i haven't found the molecular mechanism that is proposed to underlay this short depression (i did find a lot of mechanisms by which mGluR-LTD could occur, including retrograde transmitters hypothesis)
It seems to be related to a reduction in calcium influx in pre-synaptic terminals but i don't know how this can happen upon group 1 mGluR activation induced by DHPG....
First I do apologize for posting my question here. I just signed up and am quite new. I just started recording fEPSP from hippocampal CA1 region and the problem is that the signal amplitude I get is very small (between 0.2-0.5 mV). I do sagittal sectioning (300 µm) in cold ASCF and incubate for 1-1:30 h at 30 degrees. I work with 2-4 month-old mice. When I put the slices under the microscope, all the layers can be easily distinguished. The fiber valley is very very small which I think can be good sign.
I have been struggling with this problem for a couple of weeks and tried many things to get bigger signal but nothing seems to work. The last thing that recently came to my mind was that maybe there is something wrong with the stimulation protocol. This is my first recording experience and I have no idea about how to make a protocol. The one that I am currently using is the one used by one of the students in other lab for recording EPSP from cortex and is apparently working perfectly for him.
Can anyone explain what each of the following is:
First level, delta level, first duration, delta duration, digital bit pattern (#3-0) & (#7-4), train rate...
Maybe I will be able to make a protocol for hippocampal fEPSP if I have a better idea about each of the above term and the best possible range they can be within.
Also, does anyone have any recommendations for the positioning of the stimulating and recording electrodes? Is there any particular area to get the best possible response?
I do appreciate anyone's help in this regard.
Thank you all in advance
I want to do some calcium current measurements in dissociated hippocampal cultures, to make an I-V plot. I suspect the mutated protein I express, influences the VGCC-conductance. In order to isolate the calcium currents I plan on blocking the sodium-currents with TTX and use a cesium based intracellular to block the potassium currents.
My problem is choosing the cesium based intracellular medium. After doing a quick the literature I have seen several mixtures. I have seen recipes with either: Cs-glutamate, Cs-sulfate or Cs-methanesulfonate. Can someone help me by explaining these compounds?
Furthermore, I have seen some use barium instead of calcium to assess the conductance of the VGCC. Why use another ion?
Thanks in advance,
I am new into electrophysiology. I am studying LTP via a STDP protocol in whole-cell configuration, recording currents. After the LTP induction my Rs badly increases (more than 30%) but there is no change into synaptic currents. As far as i know, when Rs increases the currents should decrease following ohm law. If my currents don't decrease can be due to a potentiation into synaptic transmission?
I am using clampex 10.2 and multiclamp 700B to record from the cell, with a pipette resistance of 5 mOhm.
I hope I explained myself well,
I just get very puzzled when reading some paper results about brain slice work, when the author stimulates one intracortical region and records the response of another intracortical region, how can I know whether it is direct connection between these two regions or may involve other subcortical regions, eg the thalamus? I didn't find any evidence in the paper about preserving the thalamocortical pathway or not. How can I understand the results in these kinds of paper?
Hope anybody expert in brain slice work can help me with this. Thanks
It seems the dual virus-based monosynaptic tracing, i.e.G-TVA plus EnvA-pseudotyped deltaG RABV, is a widely used technique for seeking presynaptic partners of host cells. See (Bergami et al., 2015, Neuron 85, 710–717) and (Garcia et al., 2014, Dev Cell 30, 645-659). Is there any possibility of leakage?
As mentioned by Jim Al-Khalili in 'Life on the Edge':
The EM field, pulling together all those coherent ion channels in disparate parts of the brain to generate synchronous firing, could play a role in the transition between unconscious and conscious thoughts.
Can it be that the synchronous firing can make something visible what is not visible by asynchronous firing.
To test pre- versus postsynaptic mechanism of drug action, I am using the paired-pulse protocol. I am curious about the rationale behind altering Ca2+/Mg2+ ratio to better detect small changes. Can anyone help? How does increasing or decreasing this ratio affect PPR? I would love to know the mechanism (residual calcium hypothesis etc) behind it. Also how would this relate to synapses that show control paired-pulse depression like the medial perforant pathway in DG?
I am planing some experiments to study difference in basal synaptic transmission accross different animal conditions. I am thinking about producing a fiber volley vs fEPSP slope curve, but I haven't done this before.
Can anyone advise me for this exercise?
Regarding the x-axis of this putative curve, should I give fixed increasing steps for the stimulation intensity (for me this option seems easier) or should I try to find representative FV values (e.g. 0.05, 0.1, 0.15, 0.2, etc...; for me this option seems harder, since the FV size changes among preparations).
It would be great if you can help me.
Hi, I am trying to manipulate background synaptic release in acute brain slice.
Does anyone know how to increase background synaptic release without affecting postsynaptic dendritic active conductance too much (i.e. 4-AP increases presynptic releases but also blocks dendritic A-type channel)? What I have tried is to increase extracellular K+ from 2.5 to 3 mM, but the effect was not strong enough.
I'd be interested to know how subthreshold oscillations and noise of the inputs of a neuron are related. In particular, I would like to understand if there is some compensatory mechanism that may lead to neglect subthreshold oscillations with respect to the noise affecting synaptic inputs. This seems to me relevant to know in view of a simplified neuron model implementation for applications using very large spiking neural networks.
Do you think the animals emotional state might be responsible? Ever tried publishing, what do reviewers say?
I need to block the glutamatergic and GABAergic vesicular synaptic release in cerebellar acute slices. I would apply Tetanus Toxin. Can I expect a complete blockage of excitatory and inhibitory postsynaptic currents (whole cell recording from Purkinje Neurons)? Is there a better alternative?
NOTE - I do not want to block pharmacologically the neurotransmitter-receptors or any ion channels.
After having so many trouble with the signals I got in my rat hippocampal slices (small amplitude, poor inhibition, tendency for epileptic responses, often contamination with population spikes) I decided to try the already described protective cutting method substituting the NaCl for sucrose during the cutting procedure.
The results amazed me. The different laminar layers of the slices were clearly differentiable, and the signals were big and smooth, without any contamination by population spikes.
Now, I am naturally tempted to start working with this kind of preparation, but a paper from the group of Graham Collingridge warns that the level of LTP is lower in slices cut in sucrose ACSF, apparently due to an enhanced inhibition by GABAergic neurons (Kuenzi J Neurosci Methods. 2000 100(1-2):117-22); and raises the question I just set out. This enhanced GABAergic activity may come from a greater survival of these cells in the sucrose based procedure. However, looking through the literature, just few labs have been performing experiments under such conditions.
So, is it acceptable? Would the interpretation of my results be harder by the use of this protocol?
I rather think that this procedure better preserves both excitatory and inhibitory neurons, so it keeps the integrity of the network in a state which more closely resembles the physiological one.
I would love to know your opinion.
Thank you very much.
I have already tried adapting established methods for other animals with no success. I am using a polyclonal antibody (Sigma).
I am currently planning an acute aerobic exercise study that is likely to increase circulating levels of BDNF. However, the increase in BDNF following this type of activity is expected to be transient, returning to baseline within a few hours following the activity. What I would like to know is how long the downstream effects of a transient change in BDNF are likely to be affected. Will the cascades initiated by BDNF-trkB binding continue to be modulated after the BDNF levels have returned to baseline? If so, for how long? Any articles that relate to this topic would be welcomed.
I have read a study in which the authors labeled vesicles with quantum dots and suggested a number of times that a single vesicle can be used. What do you think about this?
I am making coronal slices and stimulating at 30% of the maximum response of my field potential.
Specifically from cortical Layer 2/3 pyramidal neurons using whole-cell patch configuration and from brain slices (2-3 weeks weeks old mice). But I don't mind any other brain area either or animal. I know of papers using excised patches but nothing in whole cell configuration.
It is known that OGD supresses fEPSPs in CA1 region, and some reports demonstrated that presynaptic A1 (A2 or A3 in another way) and Ca++ flow regulation underlined this suppression. Intracellular signaling such as PKC was also suggested. Some researchers showed that the fEPSPs suppression is irreversible if OGD for more than 10 or 30 minutes (on acute brain slices). However, in my hand, fEPSPs still can be recovered to 60% of baseline level after 45 minutes OGD insult (completely recovered if it is 30 min OGD). Any opinion for this difference? In addition, some transgenic/mutant mice generated in our lab have shown either beneficial or deleterious effect, but I did not know much about the mechanisms that accounts for fEPSPs suppression. Can anyone provide advice?