Understanding IPSC trace

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Sarah Sapouckey
Sarah Sapouckey's picture
Understanding IPSC trace

Hi, I am really new to patch-clamp recordings, and am trying to learn as much as posible by myself. I don't 100% understand how the patch-clamp recording works and so I don't really understand IPSC and EPSC traces. If an inhibitory post-synaptic potential is inhibiting and thus hyperpolarizing the neuron, why does the trace show positive changes in current amplitude? Is this because the voltage is being held constant but since the cell is becoming more negative a positive current is needed to hold the voltage study and that is the read-out of the experiment? And like-wise for negative EPSC traces. I am trying to fully understand a neuroscience paper and this is holding me back. Any help is really appreciated, thank you!

Fraser Moss
Fraser Moss's picture
IPSC sign convention

Typically IPSCs are mediated by an increase in potassium ofr chloride conductance (current out or into the cell respectively).Potassium is positively charged, and by convention net outward movement of positive charge (a positive current) from the cell under voltage clamp manifests as an outward current.Cl is negatively charged, and so by convention net inward movement of Cl manifests as outward current.Either way the evoked IPSC reduces the likelihood of an action potential because the cells membrane potantial becomes more negative when it is not under voltage clamp.  When clamped at a constant voltage, positive current is required to maintain the clamp.