Maternal and paternal plasma, salivary, and urinary oxytocin and parent–infant synchrony: considering stress and affiliation components of human bonding

Synthetic oxytocin (OT) was infused iv in four men at 3 mU/min, and the rate was doubled every 90 min for a total of three infusion periods. The mean (+/- SEM) OT MCR was 16.4 +/- 1.7 ml/kg X min and was independent of the rate of infusion. A method for measuring OT in urine was developed using an octadecasilyl-silica column for extraction of the hormone. The extracted residue was reconstituted in potassium phosphate buffer, pH 7.4, for RIA. The minimum detectable level of OT in urine was 0.2 microU/ml (defined as a bound to free ratio of approximately 90%). The mean recovery of OT was 77 +/- 2%. The mean (+/- SEM) concentration of endogenous OT in urine was 10.2 +/- 1.4 microU/ml. Endogenous OT in urine eluted from a reverse phase high pressure liquid chromatography column as a single peak of OT immunoreactivity in the position of synthetic OT. Urinary OT excretion during infusion of synthetic OT was linearly correlated with plasma OT concentration whether calculated as microunits of urinary OT per mg creatinine (r = 0.89) or urinary OT per min (r = 0.93). Mean urinary fractional clearance of OT (OT clearance/creatinine clearance) was 3.6% renal clearance of OT (5.5 ml/min or 0.43% of MCR). Thus, OT MCR was constant over a wide range of physiological plasma OT levels and was similar to MCR in pregnant women studied previously in this laboratory. Less than 1% of OT was cleared in urine. This study defines the relationship between urinary and plasma OT during steady state infusion of physiological concentrations of the hormone and indicates that measurements of OT in urine by RIA may prove helpful for pharmacokinetic and physiological studies of OT-related events in humans.

Extremely premature infants are at great risk for poor neurodevelopmental outcomes, in part because neurologic structures designed to mature in the womb must now do so in the extrauterine environment. Reliable biomarkers of neurodevelopment are especially critical in this population, as behavioral measures can be unreliable due to immaturity of the premature infant nervous system. Oxytocin (OT) has the potential to be a marker of neurobiological processes that offer infant neuroprotection. However, no studies have measured OT in the plasma and urine of premature infants. The purposes of this study were to describe plasma and urine OT levels of premature infants through 34 weeks corrected gestational age (CGA), determine whether plasma and urine OT are correlated, and explore associations between infant demographics and OT trajectories. Plasma and urine from 37 premature infants, born at gestational ages 25–28 6/7 weeks, were longitudinally collected at 14 days of life, then weekly until 34 weeks CGA. Plasma OT decreased with age, at a rate of 15% per week, and exhibited strong stability within infants. Urine OT was not correlated with plasma OT and did not show a significant trend over time; thus, urine may not be a reliable, noninvasive measurement in this population. Apgar score was the only infant demographic characteristic associated with plasma OT. Given the novelty of this work, replication is needed to confirm these findings, and future research should explore potential mechanisms (e.g., stress, normal maturation, and social experiences) that contribute to declining plasma OT levels in premature infants.

To study the relationships between fetal and maternal oxytocin (OT) levels and the initiation of labor in sheep, paired maternal and fetal plasma OT concentrations (microunits per ml) were measured by RIA. Samples were obtained daily from pregnant ewes and their fetuses for 5 days before spontaneous delivery and frequently during the first and second stages of labor and during the 3 h after delivery. The mean maternal plasma OT concentration during the first stage of labor was not different from that preceding labor. In contrast, the mean maternal plasma OT level during stage 2 of labor was significantly higher than the earlier baseline maternal values or the mean paired fetal concentration. There was no significant increase in the mean fetal plasma OT concentration before delivery. The newborn plasma OT concentration was elevated 15 min after delivery. From these data, we conclude that in the sheep, 1) the onset of labor is not associated with increased maternal plasma OT levels, 2) cervical or vaginal distension may be the stimulus for maternal OT release during stage 2 of labor, 3) an increase in the fetal plasma OT concentration does not occur before the initiation of labor or during the course of labor, and 4) stress in the final moments of labor or in early neonatal life may be responsible for elevated cord and early neonatal plasma OT levels.

Sensitive Parenting Is Associated with Plasma Oxytocin and Polymorphisms in the OXTR and CD38 Genes

Oxytocin (OT) has an important role in bond formation and social reciprocity, and animal studies indicate that OT functioning is transferred from parent to child through patterns of parental care. Perspectives on attachment suggest that the individual's various attachment bonds are underpinned by the oxytocinergic system. However, prospective human studies that demonstrate the cross-generation transfer of OT as mediated by early caregiving and its impact on children's multiple attachments are lacking. To address these concerns, the current study included 160 mothers and fathers and their firstborn child who participated in a 3-year longitudinal study. At the first and sixth postpartum months, parents' plasma OT was assayed, parent-infant interactions were videotaped and micro-coded, and allelic variations on the OXTR(rs2254298, rs1042778) and CD38rs3796863 genes were measured. At 3 years, parents' and child's salivary OT was assessed and children's social reciprocity observed during interactions with mother, father, and their first best friend. Parents' OT levels were individually stable across the 3-year period, correlated with low-risk OXTR and CD38 alleles, and predicted child OT. Child's social reciprocity with friend was associated with child OT levels, mother's OT-related genes and hormones, and mother-child reciprocity, but not with father's genes, hormones, or behavior. A cross-generation gene-by-environment effect emerged, with low child OT levels predicted by the interaction of maternal high-risk CD38 allele and diminished maternal care in infancy. These results demonstrate individual stability in peripheral OT across several years and describe a cross-generation transfer of OT through caregiving in humans within a prospective longitudinal design. Consistent with other mammals, biobehavioral experiences within the parent-infant bond shape children's affiliative biology and social behavior across multiple attachments. Our findings bear important implications for conditions involving disruptions to maternal-infant bonding and underscore the potential for peer-based interventions.

The present study investigated the involvement of the oxytocinergic neurones that project into the central amygdala (CeA) in the control of electrolyte excretion and hormone secretion in unanaesthetised rats subjected to acute hypertonic blood volume expansion (BVE; 0.3 M NaCl, 2 ml/100 g of body weight over 1 min). Oxytocin and vasopressin mRNA expression in the paraventricular (Pa) and supraoptic nucleus (SON) of the hypothalamus were also determined using the real time-polymerase chain reaction and in situ hybridisation. Male Wistar rats with unilaterally implanted stainless steel cannulas in the CeA were used. Oxytocin (1 μg/0.2 μl), vasotocin, an oxytocin antagonist (1 μg/0.2 μl) or vehicle was injected into the CeA 20 min before the BVE. In rats treated with vehicle in the CeA, hypertonic BVE increased urinary volume, sodium excretion, plasma oxytocin (OT), vasopressin (AVP) and atrial natriuretic peptide (ANP) levels and also increased the expression of OT and AVP mRNA in the Pa and SON. In rats pre-treated with OT in the CeA, previously to the hypertonic BVE, there were further significant increases in plasma AVP, OT and ANP levels, urinary sodium and urine output, as well as in gene expression (AVP and OT mRNA) in the Pa and SON compared to BVE alone. Vasotocin reduced sodium, urine output and ANP levels, although no changes were observed in plasma AVP and OT levels or in the expression of the AVP and OT genes in both hypothalamic nuclei. The results of the present study suggest that oxytocin in the CeA exerts a facilitatory role in the maintenance of hydroelectrolyte balance in response to changes in extracellular volume and osmolality.

We investigated stability and change of plasma and urinary oxytocin as well as OXTR DNA methylation patterns through psychotherapy. Furthermore, we explored the potential impact of inpatient psychotherapy on oxytocin-related biomarkers and vice versa by differentiating patients who remitted from depression versus non-remitters. Blood and urine samples were taken from 85 premenopausal women (aged 19–52), 43 clinically depressed patients from a psychosomatic inpatient unit, and 42 healthy control subjects matched for age and education at two points of time. Serum and urine oxytocin were measured using standard ELISA, and DNA methylation of the OXTR gene was assessed using bisulfite sequencing at the time of admission (baseline) and at discharge and from controls at matched time points. Oxytocin plasma levels were not associated with depression and were influenced by neither time in healthy controls nor psychotherapy in patients. Non-remitting depressed patients had significantly lower oxytocin urine levels before and after psychotherapy treatment. We found significantly lower exon 1 OTXR methylation in depressed patients over time and these differences were driven by patients remitting due to psychotherapy. A reverse pattern — higher levels of methylation in remitters — was found for exon 2 OXTR DNA methylation. Plasma oxytocin, urinary oxytocin, and OXTR DNA methylation patterns were intrapersonally relatively stable. OXTR-related factors were seemingly unaffected by inpatient psychotherapeutic treatment, but we found significant differences between remitting and non-remitting patients in urinary oxytocin and OXTR DNA methylation. If replicated, this suggests that OXTR-related markers may predict inpatient treatment outcomes of clinically depressed patients.

The influence of depressive symptomatology and perceived stress on plasma and salivary oxytocin before, during and after a support enhancement intervention

Postpartum haemorrhage (PPH) is the leading cause of maternal mortality worldwide. To prevent PPH, the WHO recommends administration of oxytocin (OT) immediately after birth, i.e. during the third stage of labour (TSL). Previous studies demonstrate that methods to quantify OT in biological matrices, e.g. enzyme-linked immunosorbent assays (ELISA), radioimmunoassays (RIA) and liquid chromatography-tandem mass spectrometry (LC-MS/MS) lack the specificity and/or sensitivity to accurately quantify OT in plasma from women administered OT during TSL. This is due to increased metabolic clearance of OT in late-stage pregnancy and at the time of childbirth, resulting in extremely low OT plasma concentrations. This study describes the development of an ultra-sensitive bioanalytical method that overcomes the issues previously reported and enables accurate pharmacokinetic analyses of exogenously administered OT in TSL. A selective and sensitive assay to quantify OT in TSL plasma was developed. Immunoprecipitation (IP) was applied to selectively extract OT from the TSL plasma, thereby generating clean extracts compatible with nanoflow LC (nLC). nLC-MS/MS was chosen for its high sensitivity and ability to differentiate between OT and potentially co-captured OT-like immunoreactive products. The presented methodology is accurate and precise, with a good linear fit between 100-10 000 fg mL-1 OT. TSL plasma samples from a clinical phase 1 study (NCT02999100) were analysed successfully, enabling OT quantification down to 100 fg mL-1. The presented IP-nLC-MS/MS method succeeded in overcoming the sensitivity challenge related to the assay of OT in TSL plasma and thereby revealing the PK profiles of OT in TSL plasma clinical study samples.

Oxytocin (OT) concentration in the blood is considered to be a marker of its action in the brain. However, two problems have emerged when measuring OT level in the blood. First, it is unclear whether different methods of assessment lead to similar OT values. Second, it is unclear if plasma OT concentrations is informative on what OT does in the brain. To clarify these issues, we collected cerebrospinal fluid (CSF) from the brain ventricle of 25 patients during surgery to compare with plasma OT after simultaneous blood withdrawal. Additionally, we collected 12 CSF and blood samples from non-human primates while awake or under anaesthesia. We used four methods to assay OT concentrations: Commercial EIA with/without extraction, laboratory developed EIA with filtration and RIA with extraction. Three of these methods showed a positive correlation between plasma and CSF OT, suggesting a link between plasma and central OT, at least under specific testing conditions. However, none of the methods correlated to each other. Our results show major disagreements among methods used here to measure peripheral and brain OT and therefore they call for more caution when plasma OT is taken as a marker of central OT.

Disclosure: A. Aulinas: None. F. Galbiati: None. M. Wronski: None. C.S. Carter: None. J. Davis: None. H.P. Nazarloo: None. K. Holman: None. G. Julia: None. E. Asanza: None. S.E. Smith: None. L. Kerem: None. F. Plessow: None. E.A. Lawson: Research Investigator; Self; received research funding and study drug from Tonix Pharmaceuticals. Background: Oxytocin (OXT)–based therapeutics, most commonly intranasal (IN) OXT, are under investigation for treating disorders ranging from obesity to osteopenia/osteoporosis, anxiety, and depression. OXT and arginine vasopressin (AVP) are structurally similar hypothalamic-pituitary “sister” peptides with physiologic actions that are shared (e.g. both suppress food intake) and opposing (e.g., OXT is anabolic while AVP is catabolic to bone; OXT reduces and AVP increases anxiety and depressive symptoms). However, the effect of chronic IN OXT administration on endogenous release of OXT and AVP into the circulation, where they can have peripheral and (through the vagus nerve) central actions, is not well established. Preclinical and short-term human studies (mostly single-dose IN OXT) suggest that exogenous OXT increases circulating OXT levels, and limited data on OXT effects on AVP levels report mixed results. Determining the effect of chronic IN OXT administration on endogenous levels of OXT and AVP is important to improve our understanding of underlying mechanisms and potential adverse effects. Leveraging a clinical trial of 8 weeks IN OXT vs. placebo in adults with obesity, we hypothesized that IN OXT would increase endogenous OXT and AVP levels. Since relative levels of OXT and AVP may impact balance of the OXT-AVP system, we also explored effects of IN OXT on the OXT:AVP ratio. Methods: We performed a randomized, double-blind, placebo-controlled trial of 8 weeks IN OXT (24 IU) 4x/day in 61 adults with obesity (stratified by sex and obesity class). Fasting plasma OXT and AVP levels were drawn prior to the morning dose of IN OXT at baseline, and weeks 4, 6, and 8. Fifty-eight participants (53% female, mean age±SD 33.6±5.8 years, body mass index 36.8±4.9 kg/m2) had plasma AVP and/or OXT measurements available at two or more timepoints and were included in our analyses. All endpoints were analyzed with linear mixed effect models including factors Time, Treatment and the interaction term Time*Treatment, controlled for biological sex and obesity class. Results: IN OXT did not impact levels of plasma OXT (coefficient, 0.45 pg/mL; 95% CI, -7.05 to 7.96), AVP (coefficient 0.59 pg/mL; 95% CI -2.81 to 4.01), or the OXT:AVP ratio (coefficient, 0.10; 95% CI, -0.17 to 0.38). Conclusions: Our data suggest that endogenous OXT and AVP levels are not impacted by 8 weeks IN OXT 4x/day, consistent with reassuring safety and tolerability data reported in clinical trials of chronic IN OXT. Effects of IN OXT are likely not mediated by changes in endogenous circulating OXT or AVP levels. Since OXT has a short half-life, it is possible that transient effects on endogenous OXT and AVP production could occur. To determine this, future studies could measure OXT and VP levels with chronic use of IN OXT closer to drug administration.Trial registration number: NCT03043053 Presentation: 6/2/2024

Ether and restraint stress-induced peripheral plasma corticotropin releasing hormone (CRH), arginine vasopressin (AVP), oxytocin (OXY) and adrenocorticotropin (ACTH) levels were measured by radioimmunoassays. Plasma CRH, AVP, OXY and ACTH rose to approximately twice the level of control rats 2 min after the onset of a 1-min exposure to ether. Plasma CRH rose further 5 min after the onset of ether stress, while plasma AVP and OXY returned to the baseline levels at 5 min. Plasma CRH, OXY and ACTH showed significant elevation 2 min after the onset of restraint stress, while plasma AVP did not show a significant change. Plasma OXY and ACTH rose further 5 min after the onset of restraint stress, whereas plasma CRH returned to baseline levels. CRH and OXY concentrations in the hypothalamic median eminence decreased 5 min after the onset of ether exposure and restraint, while the AVP concentration did not differ from control levels. The results, including the discrepancy between plasma CRH and ACTH 5 min after stress, suggest that CRH in the peripheral plasma is derived from both hypothalamic and extrahypothalamic tissues. The levels of stress-induced CRH in the peripheral plasma were sufficient to stimulate ACTH release. These results suggest that ether and restraint stress elevate plasma CRH shortly after the onset of the stress, and that this elevation in the plasma CRH level is at least partly responsible for stress-induced ACTH secretion.

HIRST, JONATHAN J.; HALUSKA, GEORGE J.; COOK, MICHAEL J.; HESS, DAVID L.; NOVY, MILES J. Author Information

Plasma, salivary, and urinary oxytocin in anorexia nervosa: A pilot study

A sensitive and specific radioimmunoassay method for simultaneous measurement of plasma arginine vasopressin (AVP) and oxytocin (OT) has been developed utilizing an extraction technique on DEAE Sephadex A25. This procedure resulted in mean recoveries of 70.7% (AVP) and 65.4% (OT) in the peptide range of 5 to 100 pg/4 ml. The sensitivity of the assay is 0.5 pg/tube for AVP and 2 pg/tube for OT. The lower limit of detection for plasma extracts was 1.2 pg AVP/ml and 5 pg OT/ml plasma. Employing this method in normal human non smokers and ad libitum fluid the basal levels (mean +/- SE) of plasma AVP are 3.5 +/- 0.2 pg/ml in males and 4.6 +/- 0.4 pg/ml in females and the basal concentrations of plasma OT are 5.1 +/- 0.3 pg/ml in males and 5.4 +/- 0.3 pg/ml in females. Dehydration and water loading produced significant changes in plasma AVP and OT concentrations and a significant correlation exists between plasma AVP and plasma (r = 0.96, p less than 0.001) and urinary (r = 0.84, p less than 0.01) osmolality, but not between plasma OT concentrations and plasma (r = 0.11, NS) and urinary (r = 0.27, NS) osmolality. These results suggest that a wide range of physiological and pathophysiological changes in plasma AVP and OT can be simultaneously measured by the extraction procedure and the radioimmunoassay described.