Membrane resistance of a neuron I am about to simulate a neuron activity with the "Leaky Integrate and Fire" neuron model. But for that I need the membrane resistance. I was really looking a lot online, but I just cant find a value.
Does anybody know the measured resistance value, or the value usually used in this model?
If there is literature that you are building off of or comparing your approach to, I would look in their papers to see what values they used and use the same. This is the standard approach, as it yields easily comparable experimental results.

If you are just looking for some ballpark numbers for less formal research, these guys used 1 mΩ, these guys did the same, and these guys say they use 10 MΩ (I think they might mean mΩ). If you want, you can also tune the model by altering this parameter until it yields expected behaviors you are looking for under conditions where you know how the model performs. Different kinds of neurons have different resistance. It's hard to be more specific without knowing more details about what you want to do.