You may fit your curve with exponential fit (as you are describing in attached fig.). It will give time course /ms that would tell similar thing what you fit straight in 1ms interval.

Hi Erik.  

We analyse slope in all our papers because the peak amplitude is often contributed to by polysynaptic pathways in our corticostriatal system. Slope is likely more representative of AMPA conductance. We use Axograph and find the maximum slope between two cursors placed at the start of the PSP and just after the peak, as a measure of maximum synaptic current. We use a sliding measurement and ensure that the slope is measured over a sample of 20 points at 10kHz sampling rate. This has held us in good stead for analysing many experiments. It is only problematic when you have  multiple components making up the ascending limb of the PSP, likely due to a number of different monosynaptic pathways of differing latencies being activated by the stimulus current and impinging upon the cell. In that case you may need to constrain the fit to one component and place your cursors around that component. We are working in vivo so this might not be a problem if you're in vitro.  

best regards 

John 

Dear Erik,

The easiest way to analyze the rise time of your EPSP traces is determining the "20-80% rise time". To do so, you measure the amplitude of your EPSP from the preceding baseline (e. g., before the stimulation artefact of your evoked EPSP), then you determine the 20 and 80% of that EPSP amplitude and make a linear fitting between these two points. This is a good estimation of the rise time of PSPs and PSCs in general, regardless of the nature of the signal. This "20-80% rise time" may be comparable to the results of more elaborated mathematical methods such as single exponential fitting and first derivative.

I hope this helps you.

Best,

I agree with Alejandro Javier. You first have to find the max amplitude of EPSP from the baseline value (determined before the stimulus artefact).Then you can look for 35-65% rise time. I normally use this time window because I work on field potential and I must avoid to peak signal from the volley potential. In calmpfit in the analysis function should be the command to set the time window 

Hi Erik,

as Alejandro pointed out before, the 20-80% rise time is most commonly used, with 10-90% on 2nd place, so I suggest you pick one of these ranges to make your data comparable to previous studies.

There is an integrated function in pClamp (Clampfit 9 and later versions I presume) called "rise slope" which you can easily use for this purpose, you just set the cursors of the search region over the whole slope of the PSP and plug in the percentages that are optimal for your data set, as Francesco suggested. Clampfit then does the work for you. If you are using Clampfit 8, you have to proceed as described here: http://mdc.custhelp.com/app/answers/detail/a_id/16557/~/pclamp:-calculate-rise-%28and-decay%29-slopes-in-clampfit Don't forget to define your baseline with another set of cursors.

Good luck!