Oxytocin is a hormone, not a neurotransmitter. It is secreted from the posterior pituitary gland, which is located in your brain. The main function of oxytocin is arguably to stimulate contractions of the muscles.
It is a crucial hormone for bonding between mother and baby, lovers, fathers, and their children, and an en-actor of any altruistic emphatic actions: to help, embrace, nurture and service- with Pleasure. People we know as compassionate, like Gandhi, Mother Theresa, Mandela, Obama, etc certainly should have more if it through their blood-stream.
The lack of Oxytocin can cause indirectly depression by a down-spiraling cascade of signals that halt and inhibit the glands that produce hormones, neurotransmitters, and life-promoting agents.
Life without Oxytocin is dry, the touch meaningless and even disgusting and repulsive, the bonds just mental, contractual and cold. It is the juice in the kiss and orgasm, and the memory of its promising repeated experience is what pushes the Evolution of hot-blooded mammals forward to bond and remain into bonds- willfully free- and enjoy while in it.