It could have the most direct effect on the amount of mitochondria in cells and also the system of the membrane.
We should expect that the rat will have have more difficulty in learning the task compared to a normal rat. This is because the rat has been injected with a certain drug that oppresses the dopamine activity. And then the rat is placed in an operant chamber where a lever-pressing task is shaped through positive reinforcement.
I believe you use the pH scale with comparing acids and bases.