• In a double-blind study, intravenous injection of naloxone, at a dose sufficient to saturate the opiate (endorphin) receptors, had no effect on sexual arousal, penile erection, ejaculation, or orgasm in a human subject. Apparently, endorphins are not involved in these phenomena.
Goldstein A, Hansteen RW. Evidence Against Involvement of Endorphins in Sexual Arousal and Orgasm in Man. Arch Gen Psychiatry. 1977;34(10):1179-1180. doi:10.1001/archpsyc.1977.01770220061006