Oxytocin — 4mg

Oxytocin is a 9-amino acid cyclic neuropeptide (Cys-Tyr-Ile-Gln-Asn-Cys-Pro-Leu-Gly, with a disulfide bridge between Cys1 and Cys6) synthesized in the paraventricular and supraoptic nuclei of the hypothalamus and released from the posterior pituitary into systemic circulation. It is evolutionarily ancient, with homologs (vasotocin, mesotocin, isotocin) present across vertebrates, suggesting a deeply conserved role in reproductive and social behavior. Its classical endocrine functions involve uterine contraction during parturition and milk ejection during lactation — roles for which synthetic oxytocin (Pitocin) has long been FDA-approved as a therapeutic agent.

The compound's more recent research profile centers on its central nervous system effects, where it acts as a neuromodulator rather than a classical neurotransmitter. Oxytocinergic projections from hypothalamic nuclei reach the amygdala, nucleus accumbens, prefrontal cortex, and brainstem regions involved in autonomic regulation. Through the oxytocin receptor (OXTR) — a GPCR coupled to Gq/G11 signaling — it influences trust formation, in-group affiliation, parent-infant bonding, pair-bonding in monogamous species, and responses to social threat. Intranasal administration has been the predominant research route for CNS effects, with subcutaneous routes also used in animal protocols.

Research applications include investigations into autism spectrum disorders (where altered oxytocinergic signaling has been implicated), social anxiety, post-traumatic stress disorder, and addiction recovery models. Findings have been heterogeneous — early enthusiasm for oxytocin as a "trust hormone" has been tempered by replication difficulties and context-dependent effects that can range from prosocial to antisocial depending on study design. The peptide has also been studied in cardiovascular research for its effects on atrial natriuretic peptide release and cardiomyocyte function. Its short plasma half-life (approximately 3–5 minutes systemically) necessitates careful pharmacokinetic design in research protocols.