A recently published study has found that females show greater brain activation to uncertain rewards during the most fertile stage of the menstrual cycle, perhaps explaining why women dress more attractively and have altered sexual preferences during this time.(link)The dopamine system is known to be involved in reward processing, and one of the current theories is that it is particularly involved in reward prediction - that is, it signals when we might expect to find something gratifying.
The key female sex hormone estrogen is known to alter dopamine function, so it was thought that females might show changes in how they experience rewards when estrogen levels fluctuate during the menstrual cycle.
The most direct dopamine-related rewards are drugs like cocaine and amphetamine, and studies have found that the same dose feels stronger during the fertile follicular phase of the cycle.