EPSP/IPSP amplitude values? I'm working with a Hodgkin-Huxley model that receives synaptic inputs from presynaptic neurons. If it receives a spike from an excitatory presynaptic neuron, the voltage of my HH neuron inceases by an amount $g$. If it receives a spike from an inhibitory neuron, the voltage jumps down by an amount $g \times K$ (so K is the factor controlling how much the voltage drops relative to how much it would increase from an excitatory neuron). I read in textbooks that the ratio of excitatory:inhibitory neurons is generally $4:1$. That implies that for the system to be "balanced", I should have $K=4$. If $K&lt;4$, then there is a net drift upwards in voltage towards the threshold values, and for $K&gt;4$, there is a net drift downwards away from the threshold. 

I have two sub-questions:

1) Is there a typical value of $g$ (the EPSP amplitude) that is biologically plausible? I've seen anywhere from $0.1-0.5$ and above which is quite a big range. I know that there is often a big range based on stimulus and whatnot, but I'm looking for a biologically reasonable value.

2) What is a typical value of $K$? In other words, what is the size of a typical IPSP amplitude relative to the EPSP amplitude? I've seen anywhere from the amplitude being the same to the amplitude being 4x the EPSP amplitude (which of course is a mighty big range).
By definition, current-based synapses are biologically implausible.  After all, biological synapses are conductance-based [1].  It is possible that current based synapses are sufficient to answer the question you are asking.  It is also possible that they are not.  Generally, biological plausibility is not a matter of the parameter values you are using but rather a matter of whether the question you are asking has biological relevance. After all, unless you have a morphologically accurate simulation including every single receptor type, etc. your model is not biologically realistic.  

The question you are asking doesn't have a good answer because you are asking a biologically non-sensical question:  what is the value of current based synapse magnitudes?
The only way one could possibly answer that question is if one knew why that question needs an answer.  Maybe you don't even need a reasonable value for the question you are trying to answer because the phenomenon is robust.  Maybe you need the answer to the fifth decimal place because your model is very sensitive to that value.   

Point is, biological realism is incredibly context-specific.

[1] Although I have heard a strange argument that the high resistance at the spine neck means that synapses are practically current sources.  I don't know anyone that relies on that.