Getting crazy with PSpice and real op.amp.

I have to measure the BIAS current in a uA741, by using the following schematic:

With real instrumentation (function generator, 20 MHz scope...) all is ok: the switch is initially closed; after some second it's open, then in output you can see the offset of sine signal decreasing up to take the falling sine signal to the saturation (negative) due to integration of the BIAS current.

Now, I have to repeat the lab with PSpice and I am not able to reproduce it such as we did it in laboratory: in Probe I get always a sine 1V/-1V without the "falling" effect...

I was wondering how I can to config PSpice in order to achieve this result; I tried to chanhe various settings with no effect. I'm using PSpice Student version.

Thanks in advance