Prolactin is primarily thought of as hormone rather than neurotransmitter. However, the central nervous system contains prolactin receptors and prolactin affects the levels of other hormones. Prolactin can affect certain dopamine and oxytocin functions.
Human
Absence of orgasm-induced prolactin secretion in a healthy multi-orgasmic male subject
Coitus-induced orgasm stimulates prolactin secretion in healthy subjects
Prolactin secretory rhythm in women: immediate and long-term alterations after sexual contact
Cardiovascular and endocrine alterations after masturbation-induced orgasm in women
Animal
Prolactin release after mating and genitosensory stimulation in females