https://www.frontiersin.org/articles/10.3389/fpsyg.2017.01520/full
According to primate studies, endogenous opioid peptide (e.g., endorphins) receptor genes have also been implicated in social relationships.
Although our results with OXTR and OPRM1 gene variants should be regarded as preliminary due to the relatively low sample size, they suggest that (1) OXTR and OPRM1 gene variants in dogs affect human-directed social behavior and (2) their effects differ between breeds.
Back off, stranger, that's my mate! The role of kappa opioid receptorshttps://blogs.scientificamerican.com/scicurious-brain/back-off-stranger-thats-my-mate-the-role-of-kappa-opioid-receptors/
Dopamine blockers lead faithful voles astrayhttps://www.newscientist.com/article/dn8412-dopamine-blockers-lead-faithful-voles-astray/?ignored=irrelevant
https://www.ncbi.nlm.nih.gov/pubmed/11292460
It has been demonstrated previously that kappa opioid receptor agonists, such as dynorphin, inhibit oxytocin secretion in the rat.
Thus, our results suggest that kappa opioid receptor agonists can exert direct inhibitory actions on oxytocin magnocellular neurons.
Dopaamie receptor agonists (i.e. apomorphine) and oxytocine are among the most studied substances that induce both penile erection and yawing
http://baillement.com/melis-ragiolas/morphine-melis.html
Prevention by morphine of apomorphine- and oxytocin-induced penile erection and yawning: involvement of nitric oxide
Oxytocin neurons are the only peptidergic neurons that develop opiate (morphine) dependence and tolerance, providing a robust model to study the cellular mechanisms of opiate addiction.
https://www.sciencedirect.com/topics/pharmacology-toxicology-and-pharmaceutical-science/kappa-opiate-receptor-agonist
This article supplements the evidence that oxytocin regulates nociception in the central nervous system. It presents additional material for clinical application of oxytocin as an analgesia drug. https://www.researchgate.net/publication/6699395_Involvement_of_Opioid_Receptors_in_Oxytocin-Induced_Antinociception_in_the_Nucleus_Accumbens_of_Rats
Involvement of Opioid Receptors in Oxytocin-Induced Antinociception in the Nucleus Accumbens of Rats