OXT and neoplasm: Pineal melatonin levels in the third ventricle not only modulate hypothalamic oxytocin [134], as melatonin also suppresses the κ-opioid receptor [135] and increases the endogenous μ-opioid receptor ligand, β-endorphin [136], indicating that the suppression of pineal (and possibly) local melatonin production will modulate the influence of the opioidergic system on patterned immune responses, including within the tumor microenvironment.