The Ecology of Humans (29-1) Oxytocin


Oxytocin is one of the neurochemical foundations of sociality in mammals. It enhances social motivation to approach and affiliate with close social partners, which constitutes the basis for the formation of any stable social bond and facilitates its maintenance over time. ~ American zoologist Teresa Romero

Oxytocin is a peptide of 9 amino acids. The hormone oxytocin is found in all vertebrates and has more ancient evolutionary roots.

In mammals, oxytocin acts in the brain as a modulator. Oxytocin is produced in the hypothalamus and its secretion regulated there.

Oxytocin is released into the blood by the pituitary gland. Oxytocin and its chemical cousin, vasopressin, are the only known hormones released by the human pituitary gland to act at a distance. Vasopressin plays a key role in homeostasis: specifically, the regulation of water, glucose, and salts in the blood.

Brain structures involved with emotions and social behaviors have dense fields of oxytocin receptors. This includes the hypothalamus, the amygdala, the anterior cingulate cortex, and the nucleus accumbens.

The hypothalamus is highly connected with other brain structures and is instrumental in sexual behaviors.

The amygdala is active while forming and storing memories related to emotional events, and fear conditioning (learning to predict aversive events).

The anterior cingulate cortex participates in error and conflict detection, and thereby associated with decisions (go/no-go).

The nucleus accumbens is lively while experiencing emotions related to pleasure, reward, laughter, addiction, fear, aggression, and the placebo effect.

There is an oxytocin receptor gene (OXTR) which has 2 variants: A (adenine) and G (guanine). People with the A variant tend toward increased sensitivity to stress, lower self-esteem, and are more depression prone. This is merely one observation that behavior and biology are intertwined. But OXTR is not destiny. And OXTR interacts with other genes as part of psychological makeup and dynamics.

Released into the bloodstream, oxytocin influences various organs, including the uterus and mammary glands.

Historically, oxytocin has been understood for its role in females, related to reproduction and maternal behaviors. Oxytocin is released in copious amounts for inducing labor, and after excitation of the nipples: stimulating milk flow for breastfeeding in nursing mothers.

Oxytocin is a chemical ingredient active in a broader expanse of behaviors, including orgasm, pair bonding, and anxiety. Oxytocin has been popularized as the “love hormone” for its profound effect on affection.

Oxytocin has various influences. Oxytocin increases with stress. Oxytocin chemically inspires trust and generosity, and reduces fear, thus affecting judgment.

Oxytocin likely affects other social emotions, including promoting envy and schadenfeude (pleasure from someone else’s misfortune). Oxytocin stimulates emotive empathy and sexual arousal in both males and females.

Elevated oxytocin impairs retrieval of unhappy memories and negatively affects learning. Animal studies indicate that oxytocin inhibits developing a tolerance to various addictive drugs (alcohol, cocaine, and opiates), and reduces withdrawal symptoms.

Autistic children have significantly low levels of oxytocin.