Is Oxytocin the “Love Hormone?” The answer coming from both human and animal research

Amanda P. Borrowa , Liza Moscoviceb, and Nicole M. Cameronab

Psychology Departmenta , Biology Departmentb, Binghamton University NY 13902

Introduction ♡ Oxytocin (OT) is a nonapeptide released from the periventricular nucleus and the supraoptic nucleus of the hypothalamus to other brain regions and indirectly to the periphery via the posterior pituitary

♡ OT receptors are located widely throughout the brain, and are found within reproductive organs, functioning in contractility during labor and orgasm ♡ During sexual arousal and orgasm in humans, plasma OT levels increase, and OT receptor-rich brain regions show activation. These same findings are shown in other species. ♡ Additionally, OT implicated in pairbonding in humans, prairie voles, and several non-human primate species ♡ Because of its presence during mating and pairbonding, OT has often been dubbed the “love hormone.” But is this an accurate description?

Animal Research ♡ Almost all animal research has focused on central OT activity ♡ The prairie vole, a monogamous species, shows greater densities of oxytocin receptors and releases more OT during mating than its promiscuous relative, the montane vole ♡ Blocking OT in prairie voles prevents pair bonding and partner preference following mating ♡ In cotton-top tamarins, a pair-bonding primate, urine OT levels positively correlated with affiliation and sex behavior

Conclusions ♡ Love has been hypothesized to be a highly developed extension of mate preference ♡ OT is involved in pair bonding and mate preference, and is released during sex, but has yet to be definitively linked to love ♡ Our findings demonstrate that OT release during mating is more complex than previously assumed ♡ The relationship between peripheral OT and central OT is not well understood

References 1.  Borrow, A.P. & Cameron, N.M. (2012) Horm. Behav.,

266-76. 2.  Fisher et al. (2006) Phil. Trans. R. Soc. B. 2173-86. 3.  Lim et al. (2004). J. Comp. Neurol. 555-70. 4.  Mens et al. (1983). Brain Res. 143-9. 5.  Schneidermann et al. (2012).

Psychoneuroendocrinology. 6.  Snowdon et al., (2010) Horm Behav. 614-8.

Our Findings ♡ Natural variations in maternal care influence sexual behavior in female offspring; mothers providing Low levels of nurturing produce more promiscuous offspring ♡ We have recently shown that OT peripheral release during mating also varies as a function of maternal care received

Human Research ♡ Most human research has focused on peripheral OT ♡ Intranasal OT improved sexual functioning in males and females in several documented case studies ♡ OT increases during arousal and peaks at orgasm ♡ A recent study found higher levels of OT in new couples than in single subjects, with lower OT levels predictive of poorer relationship quality and of separation six months later ♡ Human work on OT effects within the brain has been complicated by the fact that peripheral OT administration only results in approximately 0.002% of the hormone entering the central nervous system

♡ Preliminary fMRI work has shown activation of regions dense with OT receptors ♡ The hypothalamus, an area important for mating, is activated by romantic but not maternal love ♡ Whether OT receptors are activated, and what OT release looks like in the human brain remains to be seen

Fig. 1: Basic representation of OT release within the rodent

Fig. 2: Receiving a greater number of ejaculation increases OT in Low female offspring, but decreases OT in Highs

Fig. 3: Lordosis quotient (frequency of lordosis) positively correlated with OT in High female offspring only

Fig. 4: Receiving intromissions negatively correlated with OT in High female offspring; weak positive correlation for Lows