Pulses Of Oxytocin Research Articles

Oxytocin secretion and human parturition: Pulse frequency and duration increase during spontaneous labor in women

The secretory pattern of oxytocin was determined in blood samples taken at 1 -minute intervals for 30 minutes from 32 parturient women. The samples were collected in a manner that minimized degradation by plasma oxytocinase, and a highly specific antibody was used for the radioimmunoassay. The results indicated that oxytocin is secreted in discrete pulses of short duration. The frequency of the pulses was significantly higher during spontaneous labor than before the onset of labor. The mean pulse frequencies per 30 minutes were 1.2 ± 0.54 before labor, 4.2 ± 0.45 during the first stage, and 6.7 ± 0.49 during the second and third stages of labor. The mean pulse durations in these three groups were 1.2 ± 0.20, 1.9 ± 0.28, and 2.0 ± 0.26 minutes, respectively. The amplitude of the pulses was variable with no significant differences between the groups, the majority being around 1.0 μU/ml. The spontaneous pulses were of similar magnitude as those measured in 18 women after intravenous injections of 4 to 16 mU of oxytocin, which doses stimulated uterine contractions. We therefore conclude that the pulses of oxytocin observed at increasing frequency during spontaneous labor are of physiologic significance and provide evidence for the participation of oxytocin in the onset and maintenance of spontaneous labor. The secretory pattern of oxytocin was determined in blood samples taken at 1 -minute intervals for 30 minutes from 32 parturient women. The samples were collected in a manner that minimized degradation by plasma oxytocinase, and a highly specific antibody was used for the radioimmunoassay. The results indicated that oxytocin is secreted in discrete pulses of short duration. The frequency of the pulses was significantly higher during spontaneous labor than before the onset of labor. The mean pulse frequencies per 30 minutes were 1.2 ± 0.54 before labor, 4.2 ± 0.45 during the first stage, and 6.7 ± 0.49 during the second and third stages of labor. The mean pulse durations in these three groups were 1.2 ± 0.20, 1.9 ± 0.28, and 2.0 ± 0.26 minutes, respectively. The amplitude of the pulses was variable with no significant differences between the groups, the majority being around 1.0 μU/ml. The spontaneous pulses were of similar magnitude as those measured in 18 women after intravenous injections of 4 to 16 mU of oxytocin, which doses stimulated uterine contractions. We therefore conclude that the pulses of oxytocin observed at increasing frequency during spontaneous labor are of physiologic significance and provide evidence for the participation of oxytocin in the onset and maintenance of spontaneous labor.

Stress-related hormones affect human chorionic gonadotrophin secretion from the early human placenta in vitro

The effect of a physiological range of concentrations of three stress-related hormones, oxytocin (OT), arginine-vasopressin (AVP) and prolactin (PRL) was tested upon human chorionic gonadotrophin (HCG) secretion by placental explants from early pregnancy in static and superfusion cultures. In static cultures, OT and AVP significantly increased HCG secretion, whereas PRL had no effect. In superfusion, 1-min pulses of OT induced a significant (two- to 10-fold) rise in HCG pulse amplitude compared to the control. This effect of this neuropeptide was blocked by coadministration of a specific receptor antagonist. AVP also increased the glycoprotein pulse amplitude by two- to five-fold, but only with every second pulse administered. PRL pulses caused a progressive inhibition of spontaneous HCG pulsatility. In conclusion, stress-related hormones affect placental HCG secretion in vitro. The involvement of these factors in impairing early pregnancy development is suggested.

Pulsatile release of oxytocin into the circulation of the ewe during oestrus, mating and the early luteal phase

Two experiments were designed to investigate release patterns of oxytocin into plasma during oestrus and the early luteal phase. In Exp. 1, blood samples were collected from 5 ewes every 30 min for 10 h during 6 days around oestrus and the early luteal phase. During oestrus concentrations of oxytocin were generally low (1.27 +/- 0.54 pg/ml; mean +/- s.d.) but with occasional pulses up to 6 pg/ml. By Day 5 mean basal concentrations had risen to 4.5 +/- 2.1 pg/ml with a fluctuating release pattern. In Exp. 2, a method was developed for continuous blood sampling from conscious, unrestrained ewes. On the predicted day of oestrus following an untreated oestrous cycle, 8-ml blood samples were collected every minute for two 35-min periods (8 ewes: 16 sampling periods). For 6 ewes a ram was introduced to the pen for part of this time, and resulting behaviour was recorded. Additional blood samples were assayed for LH and progesterone to determine the stage of the cycle. Overall mean oxytocin concentrations ranged from 1.5 +/- 0.53 to 6.8 +/- 5.25 pg/ml in different animals. Ewes which were both in oestrus and exposed to the ram showed a pulsatile oxytocin release pattern consisting of low baseline concentrations with short-duration pulses superimposed (duration 1-4 min; amplitude 2.5-31.7 pg/ml; frequency 3.18/h). Coitus was not temporally associated with pulsatile release. However, the importance of the presence of the ram was indicated by total separation of 2 oestrous ewes from the ram until after experimentation. In these animals only 1 pulse of oxytocin was detected in 2.7 h of sampling. It is concluded that, although mean oxytocin concentrations at oestrus were low, short duration pulses were released into the plasma at this time. This effect may be dependent on the presence of a ram.

Variation in myometrial response to intravenous oxytocin administration at different times of the day in the pregnant rhesus monkey.

To assess a potential underlying rhythm in the sensitivity of the pregnant primate myometrium to oxytocin we infused five pregnant rhesus monkeys (gestational age, 121-142 days) with oxytocin at three different periods of the 24-h day, in the order night, afternoon, and morning, via the maternal inferior vena cava. Oxytocin was administered for 1 min every 5 min over 30 min at four doses 400, 800, 2000, and 4000 pg/min.kg. The response of the myometrium, evaluated as the number of contractions per pulse of oxytocin, was greatest in the early hours of darkness. Studies in three additional monkeys in which the order of the oxytocin challenge tests was changed, again showed that the response to oxytocin was greatest in the hours of darkness. We conclude that an underlying, as yet undefined, rhythm exists in the sensitivity of the pregnant primate myometrium to oxytocin at different times of the 24-h day. This change in myometrial sensitivity may be due to variation in one or more of the many potential regulatory sites of oxytocin's action at the cellular level. We hypothesize that this difference in myometrial sensitivity to oxytocin plays a role in the switch from myometrial contractures to contractions that occurs around the hours of darkness, e.g. postsurgery, during food withdrawal, and before delivery.

Establishment of pregnancy in sheep and pigs.

Sheep conceptuses secrete a protein, ovine trophoblast protein-1 (oTP-1), between days 10 and 21 of gestation, that is responsible for establishment of pregnancy. oTP-1 inhibits uterine production of episodic release of prostaglandin (PG) F2 alpha (PGF) necessary for luteolysis and produced in response to oestradiol and oxytocin. oTP-1 does not compete with oxytocin for binding to its receptors or interfere with oxytocin stimulation of the inositol phospholipid second messenger system after oxytocin receptors are formed. However, oTP-1 may affect synthesis of oxytocin, oestrogen and/or progesterone receptors to alter the ability of the uterus to produce episodic pulses of PGF in response to episodic pulses of oxytocin. Porcine conceptuses secrete oestrogens between days 10 and 15 of pregnancy that are essential for establishment of pregnancy. Oestrogens, directly or indirectly, alter secretion of PGF from an endocrine direction (toward the uterine vasculature) to an exocrine direction (toward the uterine lumen). PGF sequestered in the uterine lumen is unavailable to exert a luteolytic effect on the corpus luteum (CL). Pig conceptus secretory proteins stimulate uterine production of PGF and PGE, but do not appear to be responsible for inhibition of luteolysis. Conceptus secretory proteins of sheep and pigs include proteins that have antiviral activity and are considered interferons. In sheep, oTP-1 has antiluteolytic, immunosuppressive, antiviral and possibly antiproliferative properties. The specific pig conceptus secretory protein(s) possessing antiviral activity has not been established. Unlike oTP-1, however, pig interferon-like protein(s) does not appear to possess antiluteolytic activity.

Hormonal changes during luteal regression in farmed fallow deer, Dama dama.

Concentrations of progesterone, oxytocin and PGFM (pulmonary metabolite of PGF-2 alpha) were measured in plasma from peripheral blood samples collected from 5 fallow does every hour or 2 h for 12-h periods on Days 15-20 inclusive of the oestrous cycle (i.e. luteolysis). For 3 does that exhibited oestrus on Day 21, plasma progesterone concentrations fluctuated between 3 and 10 ng/ml on Days 15-18 inclusive. Thereafter, values declined progressively to attain minimum concentrations of less than 0.05 ng/ml on Day 20. Basal concentrations of plasma oxytocin and PGFM fluctuated between 5 and 20 pg/ml and 10 and 100 pg/ml respectively. Episodic pulses of plasma oxytocin (greater than 300 pg/ml) occurred on Days 15 and 16, whereas pulses of plasma PGFM (greater than 400 pg/ml) occurred on Days 19 and 20. There was little apparent correlation between episodic pulses of the two hormones. For 2 does that exhibited oestrus on Day 22, plasma progesterone concentrations declined to minimum values of 1.0-1.5 ng/ml by Day 20. One of these does showed very high levels of oxytocin secretion throughout the sampling period while the other showed an apparent paucity of oxytocin secretory periods. Two does hysterectomized on Day 13 of their second oestrous cycle failed to exhibit further oestrous cycles. Continual elevation of plasma progesterone concentrations (2-6 ng/ml) for an 8-month period indicated persistence of the corpus luteum after hysterectomy. It is concluded that luteolysis in fallow deer involves episodic secretion of both oxytocin and PGF-2 alpha.

Notions récentes concernant le corps jaune

Corpora lutea from sheep and cows as well as human and primates contain both large and small steroidogenic cells exhibiting distinct functional properties. Only the small cells seem to be able to respond in vitro to LH stimulation by raising their progesterone secretion. However, the entire progesterone secretion of the corpus luteum has been shown to be regulated in vivo by LH in the primate. The LH steroidogenic action involves the activation of membrane adenylate cyclase whose molecular mechanism has been elucidated. Then a rise in intracellular cyclic AMP induces phosphorylation by a cyclic AMP dependent protein kinase of steroidogenic protein targets which have not yet been completely identified. In sheep and cows, luteolysis is believed to be the consequence of a series of reciprocal interactions between the corpus luteum whose large cells secrete pulses of oxytocin in response to PGF2 alpha luteolysin and the endometrium which secretes pulses of PGF2 alpha in response to oxytocin. The secretion of endometrial PGF2 alpha can only begin after the induction of endometrial receptors by estradiol, from the preovulatory follicles. Similarly in women and primates luteolysis, which does not require the presence of the uterus, could be the consequence of local reciprocal paracrine interactions between luteal cells of different types. These interactions are likely to involve PGF2 alpha' oxytocin and estradiol. The biochemical mechanism responsible for the inhibition by PGF alpha of LH induced progesterone secretion in luteal cells could involve a stimulation in the cell membrane of protein kinase C and the rise of cytosolic Ca+.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of progesterone administration on the release of uterine prostaglandin F 2α and ovarian oxytocin in the goat

The effects of intramuscular progesterone administration (20 mg·day −1) on plasma concentrations of 13,14-dihydro-15-keto-prostaglandin F 2α (PGFM-pulmonary metabolite of prostaglandin F 2α) and oxytocin were examined in seventeen goats after either bilateral ovariectomy, hysterectomy or during days 12–16 of the estrous cycle. Daily mean values of PGFM in animals treated with progesterone after ovariectomy were significantly greater ( P<0.001) than in their corresponding controls on the last two treatment days (10 and 11); concentrations of oxytocin, however, remained at or near the limits of assay sensitivity. In hysterectomized goats PGFM concentrations remained extremely low and oxytocin release appeared steady rather than pulsatile. In the intact animals, undergoing luteolysis, daily mean concentrations of both PGFM and oxytocin were significantly greater ( P<0.01) in progesterone-treated goats than in their oil-treated controls; furthermore, in the progesterone-treated goats, increases in PGFM concentrations, observed after the peaks of progesterone, were either coincident with or prior to pulses of oxytocin. These results demonstrate that uterine PGF 2α stimulates the pulsatile release of oxytocin from the ovary during luteolysis in the goat.

Effects of a luteolytic dose of oestradiol benzoate on uterine oxytocin receptor concentrations, phosphoinositide turnover and prostaglandin F-2 alpha secretion in sheep.

Administration of oestradiol-17 beta benzoate on Days 9 and 10 of the oestrous cycle resulted in episodic secretion of PGF-2 alpha (as indicated by elevated circulating concentrations of 13,14-dihydro-15-ketoprostaglandin F-2 alpha) and a decline in circulating progesterone. Release of PGF-2 alpha began 35 +/- 3 h after first injection of oestrogen and progesterone concentrations declined from 42 +/- 3 h. Secretion of oxytocin, which was first observed 26 +/- 3 h after oestrogen treatment, preceded secretion of PGF-2 alpha; 69% of pulses of oxytocin coincided with episodes of PGF-2 alpha secretion. Uterine oxytocin receptor concentrations were raised in ewes treated with oestrogen, increases occurring in caruncular endometrium and myometrium by 12 h after treatment and in intercaruncular endometrium by 24 h. Raised receptor concentrations were followed at 24 h by increases in the incorporation of [3H]inositol into phosphatidylinositol and in the hydrolysis of labelled tissue phosphoinositides in response to oxytocin in slices of caruncular endometrium incubated in vitro. The following sequence of events is therefore suggested to occur at oestrogen-induced luteolysis: induction of the oxytocin receptor; increased turnover of phosphoinositides; onset of episodic secretion of PGF-2 alpha; and functional luteolysis.

Oxytocin, oxytocin-associated neurophysin, and prostaglandin F2 alpha concentrations in the utero-ovarian vein of pregnant and nonpregnant sheep.

Oxytocin, oxytocin-associated neurophysin (neurophysin), prostaglandin F2 alpha (PGF2 alpha), and progesterone concentrations were measured in the utero-ovarian vein (UOV) of sheep during the estrous cycle and early pregnancy. On days 13-16 of the cycle, large pulses of PGF2 alpha, oxytocin, and neurophysin were measured in samples collected at hourly intervals from the UOV draining a corpus luteum (UOV/CL). Most of the PGF2 alpha pulses (96.5%) coincided with a pulse of both oxytocin and neurophysin, whereas only 55.6% of oxytocin pulses coincided with a pulse of PGF2 alpha. Therefore, during luteolysis in sheep, uterine PGF2 alpha release is closely associated with ovarian oxytocin release, and oxytocin release is unlikely to be dependent upon a uterine PGF2 alpha stimulus. During frequent sampling, coincident oxytocin pulses were measured in 1) both UOVs when a CL was present in both ovaries and 2) the jugular vein, carotid artery, and UOV/CL, with a significantly higher oxytocin pulse concentration occurring in jugular venous compared with carotid arterial plasma. Pituitary and luteal release of oxytocin may, therefore, occur simultaneously and be controlled by a circulating factor in sheep. Compared to days 13-16 of the cycle, significantly (P less than 0.001) fewer pulses of PGF2 alpha, which were significantly (P less than 0.001) smaller in amplitude, were measured in UOV samples collected frequently during early pregnancy. The frequency of oxytocin pulses observed in the UOV/CL of pregnant sheep was not significantly (P greater than 0.1) different from that observed in cyclic ewes, although most (86.4%) oxytocin pulses occurred in the absence of a PGF2 alpha pulse. In contrast, when a pulse of PGF2 alpha was observed in the UOV/CL of pregnant ewes, it usually coincided with a pulse of oxytocin. The suppression of uterine PGF2 alpha release during early pregnancy is not considered to result from a lack of stimulation by oxytocin.

Pulsatile secretion of gonadotrophins, ovarian steroids and ovarian oxytocin during the luteal phase of the oestrous cycle in the cow.

All hormones were determined in blood samples collected simultaneously from the caudal vena cava and jugular vein at 20-min intervals for 12 h during the early (Day 4) and mid- (approximately Day 11) luteal phases of the oestrous cycle in 7 cows. Mean concentrations of oestradiol, progesterone and oxytocin were greater (P less than 0.01) in the vena cava than in the jugular vein. Pulses of these hormones were also more easily identifiable in the vena cava. The frequency of LH pulses was higher (P less than 0.01) during the early luteal than during the mid-luteal phase (8.0 versus 3.6 pulses/12 h). During both phases, 90-96% of all LH pulses were followed within 60 min by a pulse of oestradiol. Basal concentration and amplitude of oestradiol pulses were greater (P less than 0.05) during the early than during the mid-luteal phase. The frequency of FSH pulses was similar to that of LH during the early luteal phase (8.5 and 8.0 pulses/12 h) but was greater (P less than 0.01) than that of LH during the mid-luteal phase (6.3 versus 3.6 pulses/12 h). Thus, 41% more (P less than 0.01) FSH pulses than LH pulses were observed during the mid-luteal phase. However, the separate FSH pulses were associated with low-amplitude short-duration pulses of LH as clarified by an additional study (in 3 cows) using 5-min sampling intervals: 90-100% of all LH/FSH pulses and separate FSH pulses were secreted either concomitantly with or followed by a pulse of progesterone. However, no separate FSH pulses were associated with a pulse of oestradiol. Basal concentration and amplitude of progesterone were greater (P less than 0.01) during the mid-luteal than during the early luteal phase. The frequency of oxytocin pulses was similar to that of progesterone during the mid-luteal but not during the early luteal phase. During the mid-luteal phase 97% of all oxytocin pulses were associated with a pulse of progesterone. It is concluded that (1) separate FSH pulses are secreted in addition to parallel LH and FSH pulses during the mid-luteal phase; therefore, the frequency of secretion of LH may be modulated to a greater extent by ovarian steroids than is FSH pulse frequency; (2) pulses of progesterone are probably a result of stimulation by pulses of FSH and/or LH whereas pulses of oestradiol are caused by LH pulses; (3) ovarian oxytocin and progesterone are secreted concomitantly during the mid-luteal phase of the oestrous cycle.

Suppression of pulsatile release of oxytocin during early pregnancy in the goat

Concentrations of oxytocin were measured in the peripheral plasma of four goats during both luteolysis in the oestrous cycle and the early stages of pregnancy. The two profiles were similar, each showing a decrease from day 12 onwards; during luteolysis, however, in the non-pregnant goats this decline was characterised by frequent pulses of oxytocin in excess of 40 pg/ml; these were absent during the corresonding period of pregnancy. It is suggested that the embryo may prevent luteal regression in pregnancy by suppressing pulsatile release of oxytocin, which may be responsible for the release of prostaglandin F 2α from the uterus.

Effects of cholinoceptor antagonists on the suckling-induced and experimentally evoked release of oxytocin.

1 In the anaesthetized lactating rat, the suckling of the young causes the regular release (about every 7 min) of brief pulses of oxytocin (0.5 to 1.0 mu), which each produce a single transient increase in intramammary pressure.2 The effects of several cholinoceptor antagonists were studied in relation to this natural reflex, and also the release of oxytocin evoked by the intraventricular injection of cholinomimetics.3 Reflex milk ejection was blocked by the nicotinic antagonists mecamylamine and hexamethonium, and the inhibition was dose-dependent (ED(50) of 1 mg/kg i.v. and 5 mg/kg i.v., respectively). Despite the use of high doses, the muscarinic antagonists atropine (200 mg/kg), hyoscine (90 mg/kg) and benzhexol (30 mg/kg) all failed to prevent the reflex release of oxytocin.4 Acetylcholine (20 to 100 mug), bethanechol (0.2 to 4.0 mug) and carbachol (0.01 to 0.2 mug) injected into the cerebral ventricals stimulated a sustained release of oxytocin, which produced multiple increases in intramammary pressure. Nicotine (200 mug) was relatively ineffective by this route.5 The release of oxytocin by intraventricular bethanechol or carbachol was abolished by atropine (0.1 to 1.0 mg/kg) but not by mecamylamine (5 mg/kg) or hexamethonium (5 mg/kg).6 None of the antagonists used significantly affected either the release of oxytocin following electrical stimulation of the neurohypophysis or the mammary sensitivity to endogenous or exogenous oxytocin.7 The results suggest that the neural pathway controlling the reflex release of oxytocin during suckling in the rat contains a cholinergic component, which acts through nicotinic receptors. A second cholinergic pathway, of the muscarinic type, may also exist. The role of these two pathways is discussed.

Plasma concentrations of prolactin and thyrotrophin during suckling in urethane-anaesthetized rats.

Plasma levels of prolactin and TSH were determined by radioimmunoassay in urethaneanaesthetized lactating rats during suckling. Oxytocin release was monitored by recording intramammary pressure. Application of ten pups, 3 h after administration of urethane (1-1 g/kg, i.p.), evoked a parallel rise in prolactin and TSH concentrations which reached a maximum during the 3rd hour of suckling and then declined. Peak hormone concentrations represented a 25-fold increase in prolactin and a ten-fold increase in TSH. Suckling also elicited a pulsatile (every 5-10 min) release of 0-5--1-0 mu. oxytocin. The gradual rise in prolactin and TSH occurred between the 1st and 20th oxytocin pulses. Intravenous injection of thyrotrophin-releasing hormone (TRH) into unsuckled, anaesthetized lactating rats resulted in a 7- to 30-fold increase in TSH concentration, whereas prolactin levels showed no substantial change. These results indicate that suckling releases TSH as well as prolactin in the urethaneanaesthetized rat. However, the absence of prolactin release after injections of TRH makes it unlikely that both endocrine responses are regulated solely by the actions of this one releasing hormone.

Electrophysiological evidence for the activation of supraoptic neurones during the release of oxytocin.

1. Antidromically identified supraoptic (SO) units were recorded in lactating rats anaesthetized with urethane (1.1 g/kg), and their activity was studied during milk ejection evoked by the suckling of the young. Fifty-eight SO units were recorded through 174 milk ejections. Each milk ejection was the result of a neurohypophysial release of an oxytocin pulse of 0.5-1.5 m-u.2. Fifty-five of the SO units displayed background activity and three were silent. The firing rates ranged from 0 to 15.4 spikes/sec, the distribution was exponential with 26% of the units firing at < 1 spike/sec. Sixteen (28%) of the SO units displayed a phasic pattern of activity characterized by periods of activity (6-132 sec) and silence (4-71 sec).3. Twenty-five of the non-phasic units displayed a large and stereotyped acceleration in spike activity some 10.5-17.4 sec before the rise in intramammary pressure at milk ejection. Units accelerated to rates between 9-66 spikes/sec, an increase of about thirtyfold (median) on background activity. The response was brief (0.9-4.7 sec) and was followed by a period of after-inhibition.4. It was concluded from studies of double recordings and observations of multi-unit activity that all the responsive units were synchronously activated. The mean latency of 13.3 sec between the onset of the neurosecretory response and milk ejection was similar to that observed following the experimental release of endogenous oxytocin by electrical stimulation of the neurohypophysis (50 pulses/sec for 2-4 sec).5. Four of the phasically active units were correlated with the oxytocin release for milk ejection. Three of these units displayed a burst of activity superimposed on the terminal portion of an active phase, some 10.2-14.7 sec before milk ejection. The fourth unit, recorded in conjunction with a responsive non-phasic unit, consistently switched from silence to activity coincident with the onset of the SO activation.6. The remaining SO units and a further ten units that were not antidromically activated by neurohypophysial stimulation displayed no change in activity during either the period of neurosecretory activation or the period of after-inhibition.7. This activation of the SO neurones, in the formulation of oxytocin release and milk ejection, is the same as that we have previously observed in recordings from the paraventricular (PV) region, and the proportion of neurones displaying the response is similar: 48% in the SO nuclei, 58% in the PV nuclei. We conclude, since the SO nuclei contain 80% of the neurosecretory cells that project to the neurohypophysis, that the SO nuclei are as important, if not more so, than the PV nuclei in the control of oxytocin release.

Electroshock Therapy for Depression: Report of 200 Cases

The hypothalamic hormone oxytocin (OXT) plays an important role in a range of physiological processes and social-emotional functioning in both sexes. In women, physiological stimuli, such as suckling and parturition, result in pulsatile release of OXT into the peripheral circulation via the posterior pituitary gland. However, data regarding OXT secretory patterns in men during a state of rest are limited. Further, the relationship between secretory dynamics of OXT and emotional measures has never been evaluated. We hypothesized a pulsatile pattern of OXT secretion in men, and explored the relationship between OXT secretory patterns and social-emotional functioning.Deconvolution analysis was performed on serum OXT levels obtained every 5 min over a period of 10 h in 5 healthy normal weight men. Area under the curve (AUC), average OXT values, and pulse characteristics [pulse number, inter-pulse interval, pulse height and mass (area under each pulse)] were calculated. State Adult Attachment Measure (SAAM) assessed types of human attachment. Interpersonal Support Evaluation List (ISEL) assessed perception of social support. Toronto Alexithymia Scale (TAS-20) measured the ability to express and identify one’s own emotions.Mean age was 22.8 ± 1.2 years, and BMI was 21.7 ± 0.4 kg/m2 (mean ± SEM). Assuming a basal secretion of zero and a half life of five to seven minutes, we demonstrated the following: OXT AUC: 5421 ± 1331 pg/ml, mean OXT level: 9.1 pg/ml, mean pulse number: 22 ± 3/10hr, mean pulse height: 1.81 ± 0.48 pg/ml, mean pulse mass: 30.34 ± 10.29 pg/ml and mean inter-pulse interval: 27 ± 4 min. The SAAM Avoidant scale correlated negatively with mean OXT pulse height (r = −0.90, p = 0.04) and pulse mass (r = −0.95, p = 0.01). The ISEL Belonging score correlated positively with OXT AUC (r = 0.89, p = 0.04) and average OXT (r = 0.93, p = 0.02). ISEL Appraisal score also had a positive association with mean OXT pulse height (r = 0.99, p = 0.0006) and pulse mass (r = 0.98, p = 0.003). Finally, ISEL total score had a significant correlation with average OXT values (r = 0.90, p = 0.04). While none of the subjects had a score in the alexithymia range, TAS-20 Difficulty describing feelings score had an inverse correlation with OXT pulse height (r = −0.96, p = 0.01) and pulse mass (r = −0.99, p = 0.001). TAS-20 total score also had an inverse correlation with OXT pulse height (r = −0.94, p = 0.02) and pulse mass (r = −0.96, p = 0.009).We demonstrate a pulsatile pattern of peripheral OXT secretion in healthy men at rest. Subjects with lower OXT pulse height and pulse mass had a more avoidant style of attachment, felt less supported, and expressed greater difficulty in describing their feelings. Our findings support the concept that OXT is a key mediator of social-emotional functioning. Future studies to determine causality are warranted.