Kerstin Uvnäs-Moberg

Physiological and Endocrine Effects of Social Contact

Nonnoxious sensory stimulation associated with friendly social interaction induces a psychophysiological response pattern involving sedation, relaxation, decreased sympathoadrenal activity, and increased vagal nerve tone and thereby an endocrine and metabolic pattern favoring the storage of nutrients and growth. It is suggested that oxytocin released from parvocellular neurons in the paraventricular nucleus (PVN) in response to nonnoxious stimulation integrates this response pattern at the hypothalamic level. The response pattern just described characterized by calm, relaxation, and anabolic metabolism could be regarded as an antithesis to the well known fight-flight response in which mental activation, locomotor activity, and catabolic metabolism are expressed. Furthermore, the health-promoting aspect of friendly and supportive relationships might be a consequence of repetitive exposure to nonnoxious sensory stimulation causing the physiological endocrine and behavioral changes just described.

High doses of oxytocin cause sedation and low doses cause an anxiolytic-like effect in male rats.

The aim of the present investigation was to explore dose relationships for effects of oxytocin on spontaneous motor activity in the rat. Oxytocin in doses from 1-1000 micrograms/kg was given SC to male Sprague-Dawley rats, and spontaneous motor behavior was measured by means of photocell-operated open-field observations. In the rats treated with low doses of oxytocin (1-4 micrograms/kg), there was a decrease in peripheral locomotor activity. With increasing doses (250-1000 micrograms/kg), there were clear signs of sedative effects as indicated by a suppression of locomotor activity and rearing. The time course for the effect of oxytocin on peripheral activity (1 microgram/kg) and rearing (1 mg/kg) was tested. A maximal effect was obtained within 1 h and, thereafter, the behavior gradually returned to normal within 24 h. This spectrum of effects caused by oxytocin was similar to that of midazolam but different from that induced by raclopride.

Oxytocin Causes a Long-Term Decrease of Blood Pressure in Female and Male Rats

The aim of the present study was to investigate the long-term effects of oxytocin (OXY) on blood pressure (BP) and heart rate (HR) in conscious female and male rats. For this purpose, subcutaneous (SC) (0.01, 0.1, and 1 mg/kg) or intracerebroventricular (ICV) (1 microgram/kg) injections of OXY were given during 5-day periods. BP and HR were measured daily. A significant decrease in BP, without affecting HR, compared to saline-treated controls was seen in response to 0.1 (males: p < 0.01, females: p < 0.001) and 1 mg/kg (p < 0.001) of OXY given SC. BP gradually returned to preexperimental levels within 10 days after the last injection in male rats but, in females, the significant lowering of BP remained unchanged during this period. Also OXY ICV (1 microgram/kg) decreased BP (p < 0.05 after one day, p < 0.001 after 5 days of injections). This effect was still present 8 days after the last injection (p < 0.05). These results indicate that OXY may induce a long-term lowering of BP.

Different patterns of oxytocin, prolactin but not cortisol release during breastfeeding in women delivered by Caesarean section or by the vaginal route

The aim of this study was to find out whether the hormonal patterns of oxytocin, prolactin and cortisol differed between women delivered by emergency section or by the vaginal route and if these patterns show any relation to the duration of breastfeeding. Seventeen mothers with emergency section (C.S.) and 20 mothers with normal vaginal deliver (V.D.) were blood sampled in connection with breastfeeding on day 2 post partum for oxytocin, prolactin and cortisol. The number of oxytocin pulses as calculated with the PULSAR program occurring during the first 10 min of the breastfeeding session varied between 0 and 5. The V.D. mothers had significantly more pulses than the C.S. ones. Furthermore the C.S. women lacked a significant rise in prolactin levels at 20-30 min after the onset of breastfeeding. Logistic regression analysis revealed mode of delivery and infants age at first breastfeed to be the most important, independent variables showing a relation to the release pattern of oxytocin on day 2. Correlations between oxytocin pulsatility on day 2 and the duration of the exclusive breastfeeding period in the V.D. group suggest that development of an early pulsatile oxytocin pattern is of importance for breastfeeding.

SOCIAL ISOLATION AND CARDIOVASCULAR DISEASE: AN ATHEROSCLEROTIC PATHWAY?

This paper outlines two pathways through which social support can influence the prevention or progression of cardiovascular disease: health behaviors and neuroendocrine mechanisms. Its primary focus is on neuroendocrine pathways, reviewing data which suggest that lack of social support is etiologically related to coronary artery lesion development through two mechanisms: sympathetic-adrenomedullary influences on platelet function, heart rate and blood pressure in the initial endothelial injury; and pituitary-adrenal cortical factors involved in smooth muscle cell proliferation during progression of the lesion after injury has taken place. It hypothesizes that the buffering effect of social support on the cardiovascular system is mediated primarily through mechanisms associated with the release of oxytocin.

Skin‐to‐skin contact may reduce negative consequences of “the stress of being born”: a study on temperature in newborn infants, subjected to different ward routines in St. Petersburg

Aim: To evaluate how different delivery‐ward routines influence temperature in newborn infants. Methods: A total of 176 newborn mother‐infant pairs were included in a randomized study. The babies were kept skin‐to‐skin on the mothers chest (Skin‐to‐skin group), held in their mothers arms, being either swaddled or clothed (Mothers arms group), or kept in a cot in the nursery, being either swaddled or clothed (Nursery group). Temperature was measured in the axilla, on the thigh, back and foot at 15‐min intervals at from 30 to 120 min after birth. Results: During this time period the axilla, back and thigh temperatures rose significantly in all the treatment groups. The foot temperature displayed a significant fall in the babies in the Nursery group and this decrease was greatest in the swaddled babies. In contrast, foot temperature rose in the babies in the Mothers arms group and in particular in babies in the Skin‐to‐skin group. Foot temperature remained high in the Skin‐to‐skin group, whereas the low temperature observed in the Nursery group gradually increased and two days after birth the difference was no longer significant.

Anti-nociceptive effects of oxytocin in rats and mice

The existence of neural opioid-mediated networks that are specific for the modulation of nociception is well established. Parallel non-opioid pathways exist, but their underlying physiology is little known. We now report that oxytocin administered intraperitoneally to rats, and intraperitoneally or intracisternally to mice has an anti-nociceptive effect, which is related to the activation of descending anti-nociceptive pathways. This anti-nociceptive effect can be reversed by an oxytocin antagonist but not by the opioid antagonist naloxone. The anti-nociceptive effect of oxytocin is not directly dependent on the activation of serotonergic pathways or to changes in temperature. Our data indicate that the oxytocinergic system has a modulatory function on nociception.

Oxytocin causes a sustained decrease in plasma levels of corticosterone in rats

The aim of this study was to investigate how oxytocin (OXT) influences plasma levels of ACTH and corticosterone in rats. A single injection of OXT (1 mg/kg s.c.) caused a transient increase in ACTH and corticosterone. In contrast, 1 mg/kg OXT (but not 10-100 microg/kg) decreased corticosterone, but not ACTH levels, 6 h after the injection. OXT (1 mg/kg s.c.) administered once a day for 5 days, decreased cortiocosterone for 10 days after the last injection. An acute challenge with ACTH increased corticosterone to the same level in rats pretreated with OXT and controls. Dexamethasone decreased corticosterone to equal levels in both groups. Thus, OXT seems to be able to stimulate as well as to inhibit the activity within the HPA-axis within a short- and a long-term perspective, respectively.

Oxytocin as a possible mediator of SSRI-induced antidepressant effects

Abstract The nonapeptide oxytocin is released into systemic circulation in situations of psychosocial interaction, and has been shown to be involved in mechanisms of social bonding and social recognition in laboratory studies. In view of disturbances in psychosocial relationships being a triggering factor for depression and anxiety, it is interesting to note that experimental studies have shown oxytocin to possess antidepressant- and anxiolytic-like actions. Thus, in the present study we examined effects of the SSRI citalopram (20 mg/kg IP) on plasma oxytocin, acutely and upon repeated administration, in adult male Sprague-Dawley rats. Plasma oxytocin, and some functionally related peptides (CCK, gastrin, somatostatin and insulin), were measured by standard radioimmunoassay techniques. Acute citalopram administration produced a statistically significant increase in plasma oxytocin and CCK levels. Administration of citalopram for 14 days did not attenuate the oxytocin-releasing effect to a challenge dose of the SSRI zimeldine (20 mg/kg SC), whereas CCK levels were not increased after the subchronic citalopram treatment. Thus, the SSRI citalopram produces increased plasma oxytocin levels acutely, and there appears to be no or little tolerance to this effect upon repeated administration. There were no, or variable, effects on plasma levels of gastrin, somatostatin or insulin. It is suggested that oxytocin release is an important aspect of the pharmacological actions of SSRIs, and this could be an important contributory factor for the clinical profile of this group of antidepressants with particular efficacy in disorders of psychosocial origin.

Oxytocin, prolactin, milk production and their relationship with personality traits in women after vaginal delivery or Cesarean section

The aim of the present study was to investigate if personality profiles reflecting anxiety and social interaction of mothers who delivered by Cesarean section (CS) or by the vaginal route (VD) differed in early postpartum and to investigate whether these personality traits were correlated with hormonal data. Seventeen women delivered by emergency CS and 20 by the vaginal route were selected for this study. The amount of milk transferred to the baby was measured. Blood samples were collected during the second breast-feeding on the second day after delivery. The samples were analysed for oxytocin and prolactin. After breastfeeding, the mothers were asked to fill in the personality inventory, Karolinska Scales of Personality (KSP). The scores were compared between the two groups and with a normative group of women. Each scale on the personality inventory was correlated with hormonal parameters. The KSP showed significant differences between the delivered mothers and the normative group in variables related to anxiety and socialization. The VD mothers deviated more than the CS mothers from the normative group. Correlations with hormonal data indicated that anxiety was inversely related with basal levels of oxytocin and prolactin in the CS mothers, whereas the pulsatility of oxytocin was related to social desirability in both groups. Social desirability and oxytocin pulsativity were also correlated with the amount of milk transferred from the mother to the baby. The correlations indicate that central oxytocin, as reflected by basal plasma levels and patterns, may be involved in behavioral adaptations to the maternal role.