^^^ This was pulled directly from my neuroscience text book, minus citations, because that would take too long to type. If anyone really wants those, I'll edit my post and include a bibliography of the cited parts.
"Biological Psycology" 8th. ed.; Kalat, James. W
"In moderate concentrations, dopamine stimulates mostly type D1 and D5 receptors, which facilitate erection of the penis in the male and sexually receptive postures in the female. In higher concentrations, dopamine stimulates type D2 receptors, which lead to orgasm. The effects at D1 and D2 receptors tend to inhibit each other. As a result, the early stages of sexual excitement are characterized by arousal but not orgasm; the late stage is marked by orgasm and then a decrease in arousal.
Whereas dopamine stimulates sexual activity, the neurotransmitter serotonin inhibits it, in part by blocking dopamine release. Many popular antidepressant drugs increase serotonin activity, and one of their side effects is to decrease sexual arousal and impair orgasm."
I will post my stipulations later. Right now, I have to go to class...
...discuss amongst yourself.
~Decibel