Oxytocin Peptide Overview

Oxytocin may have relevance in widespread areas of study. Though Oxytocin levels are at their highest during nursing and birth in various gestational organisms, research indicates they may also be elevated in scenarios of social bonding. For this reason, studies have suggested that Oxytocin may support libido.

It seems this is accomplished by regulating the activation of circuits that motivate caloric intake. The ventral tegmental region (VTA) is a component of this route and the site of dopaminergic organism formation. The VTA also has Oxytocin receptors, and it is thought that the impact of reduced food demand is caused by Oxytocin exposure that saturates these receptors.

Oxytocin: Mechanism of Action

Recent studies have suggested that the hypothalamic neuropeptide hormone Oxytocin may be important in controlling hunger and weight via the central nervous system. It is deemed crucial to research the mechanisms of Oxytocin's anorexigenic impacts if this neurohormonal weight loss compound is to be considered. One study aimed to evaluate the impact of Oxytocin.

Researchers postulated that Oxytocin might dampen the ventral tegmental area's (VTA) response to visual cues representing high-calorie food instead of non-food stimuli. The VTA is the birthplace of the mesolimbic dopaminergic reward system. In response to stimuli involving high-calorie foods, research models under observation that were exposed to Oxytocin appeared to have had bilateral VTA hypoactivation, in contrast to the control group.

According to a secondary exploratory whole-brain analysis, hyperactivation in cognitive control (anterior cingulate and frontopolar cortex) and hypoactivation in additional hedonic (orbitofrontal cortex, insula, globus pallidus, putamen, hippocampus, and amygdala) and homeostatic (hypothalamus) food motivation regions were found following Oxytocin exposure compared to controls.

The BOLD signal in reward-related food motivation brain areas appeared reduced after Oxytocin exposure, suggesting a possible neurobiological explanation for the anorexigenic impacts of Oxytocin in animal models. The results also imply that cognitive control areas, deemed essential for controlling food intake and emotional conflict resolution, seem more activated after Oxytocin exposure, but homeostatic regions appear less activated. More research is needed to establish a connection between these alterations in brain activity and the impacts of Oxytocin on appetite and weight.

Oxytocin: Chemosensors

Although speculation of social chemo-signaling in research models is mounting, current understanding of the processes involved is limited. Two chemo signals, androstane-4,16,-dien-3-one and extra-1,3,5 (10),16-tetraen-3-ol, respectively, convey femininity to the targeted recipients.

Researchers investigated whether the two neuropeptides, Oxytocin and Vasopressin, are involved in subconsciously processing these signals, considering their evolutionarily conserved roles in reproductive and social behaviors, respectively. Atosiban, a competitive antagonist of both Oxytocin and Vasopressin receptors, consistently blocked chemosensory communications, according to psychophysical data. In contrast, Oxytocin was hypothesized to have affected androstadiene and estratetraenol decoding in concentration-dependent, nonmonotonic ways that were reliant on the social proficiency of the receivers, whereas Vasopressin had no such impact. When considered as a whole, these results suggest that neuroendocrine parameters are directly related to the subliminal chemosensory communications between sexes.

Oxytocin: Reproductive Function

Studies suggest that the paraventricular nucleus of the hypothalamus contains oxytocinergic neurons that regulate erectile function and sexual behavior in animal models. These neurons project to locations beyond the hypothalamus and the lumbar spinal cord. An important part of the neurological circuits that regulate penile reflexes in rats, sometimes called the "spinal ejaculation generator (SEG)" circuits, is the gastrin-releasing peptide (GRP) system located in the lumbosacral spinal cord. In this study, scientists looked at how the SEG neurons in rats communicate with the hypothalamic-spinal Oxytocin pathway.

This study reports that Oxytocin may activate SEG/GRP neurons that express Oxytocin receptors, which are involved in sexual behavior. Both the amount of ejaculation and the behavior preceding it seem affected by presenting an Oxytocin receptor antagonist intrathecally during normal sexual engagement. Axonal varicosities near the plasmalemma suggested Oxytocin-neurophysin immunoreactivity in electron microscopy of potassium-stimulated acute lumbar cord slices. No electron-lucent microvesicles or thickenings of the synaptic membrane were observed in these areas. Based on these findings, it appears that Oxytocin may be released in the lumbar spinal cord of rats not only through conventional synapses but also through exocytosis of dense-cored vesicles from axonal varicosities. Then, it reaches the Oxytocin receptors on GRP neurons through diffusion, a form of localized volume transmission, and may impact sexual function. Scientists interested in Oxytocin are encouraged to visit www.corepeptides.com.

References

[i] Magon N, Kalra S. The orgasmic history of oxytocin: Love, lust, and labor. Indian J Endocrinol Metab. 2011 Sep;15 Suppl 3(Suppl3):S156-61. doi: 10.4103/2230-8210.84851. PMID: 22029018; PMCID: PMC3183515.

[ii] Kepu Chen, Yuting Ye, Nikolaus F Troje, Wen Zhou (2021) Oxytocin modulates human chemosensory decoding of sex in a dose-dependent manner eLife 10:e59376 https://doi.org/10.7554/eLife.59376

[iii] Plessow F, Marengi DA, Perry SK, Felicione JM, Franklin R, Holmes TM, Holsen, LM, Makris N, Deckersbach T, Lawson EA. Effects of Intranasal Oxytocin on the Blood Oxygenation Level-Dependent Signal in Food Motivation and Cognitive Control Pathways in Overweight and Obese Men. Neuropsychopharmacology. 2018 Feb;43(3):638-645. doi: 10.1038/npp.2017.226. Epub 2017 Sep 20. PubMed PMID:28930284; PubMed Central PMCID: PMC5770767.

[iv] Diven, Liany C et al. “Oxytocin discontinuation during active labor in women who undergo labor induction.” American journal of obstetrics and gynecology vol. 207,6 (2012): 471.e1-8. doi:10.1016/j.ajog.2012.08.035

[v] Rabow, S., Hjorth, U., Schönbeck, S. et al. Effects of oxytocin and anaesthesia on vascular tone in pregnant women: a randomized, double-blind placebo-controlled study using non-invasive pulse wave analysis. BMC Pregnancy Childbirth 18, 453 (2018).