The effect of oxytocin on hand blood flow in man following total and sympathetic nerve block

Oxytocin and the warm outer glow: Thermoregulatory deficits cause huddling abnormalities in oxytocin-deficient mouse pups

Oxytocin is a social and reproductive hormone that also plays critical roles in a range of homeostatic processes, including thermoregulation. Here, we examine the role of oxytocin (OT) as a mediator of brown adipose tissue (BAT) thermogenesis, cold-induced huddling, and thermotaxis in eight-day-old (PD8) OT 'knock out' (OTKO) mouse pups. We tested OTKO and wildtype (WT) pups in single- and mixed-genotype groups of six, exposing these to a period of ambient warmth (~35°C) followed by a period of cold (~21.5°C). Whether huddling exclusively with other OTKO or alongside WT pups, OTKO pups showed reduced BAT thermogenesis and were significantly cooler when cold-challenged. Huddles of OTKO pups were also significantly less cohesive than WT huddles during cooling, suggesting that thermoregulatory deficits contribute to contact abnormalities in OTKO pups. To further explore this issue, we examined thermotaxis in individuals and groups of four OTKO or WT pups placed on the cool end of a thermocline and permitted to freely locomote for 2h. When tested individually, male OTKO pups displayed abnormal thermotaxis, taking significantly longer to move up the thermocline and settling upon significantly lower temperatures than WT pups during the 2h test. OTKO mouse pups thus appear to have deficits in both thermogenesis and thermotaxis-the latter deficit being specific to males. Our results add to a growing body of work indicating that OT plays critical roles in thermoregulation and also highlight the entanglement of social and thermoregulatory processes in small mammals such as mice.

Changes in breast skin temperature during the course of breastfeeding

Breast skin temperature was measured during breastfeeding in 11 mothers on a total of 47 occasions, using a Coretemp CM-210 (Terumo Corp, Tokyo, Japan), to examine the changes of breast skin temperature during the course of breastfeeding. In both breasts, the breast skin temperature was significantly higher than the baseline skin temperature from the beginning of suckling up to 5 minutes after completion of suckling, and the mean breast skin temperature before breastfeeding between 4 days and 8 weeks postpartum was significantly higher than that on the first 1 to 2 days postpartum. These results show that the breast skin temperature increases between the first 1 to 2 days and 4 to 5 days postpartum and that breast skin temperature remains high during suckling and up to 5 minutes after the completion of suckling. These findings will be useful for educating mothers during the perinatal period on the normal course of breastfeeding by individual instruction or in classes.

The effect of oxytocin on blood vessels of cremaster muscle of the rat

Oxytocin administered intravenously to the anaesthetized rat produced dilatation of the blood vessels of the cremaster muscle at concentrations ranging from 2.5 times 10-minus 11 to 2.5 times 10-minus 9 M. When applied topically to the exposed vessels it produced constriction at concentrations ranging from 2.5 times 10-minus 12 to 5.0 times 10-minus 8 M. Oxytocin was thus similar to adrenaline in eliciting opposite effects when applied to the serosa or to the intima of skeletal muscle blood vessels.