How does constriction of afferent and efferent arterioles affect the glomerular filtration rate? I think I know that afferent constriction will decrease the GFR. But what about efferent constriction? Uworld seems to be saying that efferent constriction would increase the GFR, but I found a review online saying: 

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  The net result of efferent arteriolar constriction is an increased filtration fraction. **The GFR most likely decreases** because the RBF decreases, but the decrease in the GFR will not be proportionate because of the increase in glomerular capillary pressure.

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So which is it? and why?