Hi Dr. Vickery,
We use horizontal brain slices and stimulate thalamic afferent fibres (not the CT fibres). I will place the stimulating electrode differently next time before recording, maybe slightly further away. We tried replacing the electrode because until a few weeks back, all the cells recorded from horizontal slices using the same stimulating and recording set up gave synpatic responses without the antidromic spikes. The only thing that has changed is the electrode as part of a routine replacement. (We use orthodontic resin to stick together two tungsten stimulating electrodes from AM systems).
----- Original Message -----
From: "Richard Vickery" <Richard.Vickery from unsw.edu.au>
To: neur-sci from magpie.bio.indiana.edu
Sent: Sunday, March 20, 2011 10:54:13 PM
Subject: [Neuroscience] Re: Avoiding antidromic spike during synaptic stimulation
There's usually not a lot of difference between the axon activating parameters,
so changing electrodes won't separate out your input axons from the ones
originating from the neuron you are recording from.
I don't know about the geometry of your thalamic slice, but what you want is to
be on an input pathway and not on an output pathway. You will more likely get
success hunting around for a better stimulus site than by changing electrodes.
On 20/03/2011 2:00 PM, Yamini Venkataraman wrote:
>> I record synaptic responses in thalamic neurons in brain slices using whole
> cell patch clamp. The stimulating electrode is a bipolar parallel stimulating
> electrode (separation ~ 1 mm) and this generally works well in evoking
> synaptic responses. Off-late, there has been a huge antidromic spike in every
> cell that is visible just prior to the PSP. Its not clear why the antodromic
> spike is being generated, even when the stimulating electrode is well
> separated from the recording electrode. Nothing in the set-up has changed
> except for replacing the stimulating electrode with an identical new one.
> Since then, we have tried several new electrodes and even replaced the GRASS
> stimulator to eliminate the antidromic spike but its always present.
>> This problem is not there with a bipolar concentric stimulating electrode,
> that generates a short duration stimulus artifact, but unfortunately that
> does not evoke synaptics in most cells even at the highest stimulating
>> It would be very helpful to hear any suggestions for eliminating the
> antidromic spike.\
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