Prolactin is primarily thought of as a hormone rather than a 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
No evidence for prolactin’s involvement in the post-ejaculatory refractory period