Oxytocin
Oxytocin (Oxt) is a peptide hormone and neuropeptide. Oxytocin is normally produced by the paraventricular nucleus of the hypothalamus and released by the posterior pituitary. It plays a role in social bonding, sexual reproduction, childbirth, and the period after childbirth. Oxytocin is released into the bloodstream as a hormone in response to stretching of the cervix and uterus during labor and with stimulation of the nipples from breastfeeding. This helps with birth, bonding with the baby, and milk production. Oxytocin was discovered by Henry Dale in 1906. Its molecular structure was determined in 1952. Oxytocin is also used as a medication to facilitate childbirth.
Sexual desire and intimate relationships
Much like the opioids mentioned above, the neuropeptide oxytocin has been shown to be extremely affective in the conditioning effects involved in the formation of stable preferences for places, stimuli and other beings. Studies have shown that women specifically not only show greater sensitivity to the release of oxytocin during sexual activity than men, but it has been suggested a correlation exists between oxytocin release and orgasm intensity, which may explain why women generally associate stronger interconnectivity between love and sexual desire.