Studies in several central effects of oxytocin in lactating rats

催产素是一种在下丘脑室旁核和视上核产生的激素，由垂体后叶分泌，据报道也在脑内分泌，参与多种脑功能。本研究旨在探讨催产素在大鼠摄食和运动中的脑功能。首先，研究催产素对神经肽Y(NPY)和刺鼠相关蛋白(AgRP)诱导的摄食的影响。Wistar雄性大鼠经皮下埋管注入催产素(1nmlo/5ul，icv)或生理盐水，30min后分别注入NPY、AgRP(1nmlo/5ul，icv)或生理盐水。第二次注射后监测1h和2 h的摄食量，催产素不影响NPY和AgRP诱导的摄食量，但显著减少生理盐水处理大鼠的基础摄食量。在…中注射催产素的时间正常雄性或去卵巢(OVX)雌性大鼠的下丘脑腹内侧核(VMH)在转轮中的运动活动明显增加。17β-雌二醇(17-雌二醇，E_2)可增强催产素对去卵巢大鼠的这种作用。去卵巢大鼠VMH中催产素受体(OTRmRNA)的表达在E2处理后2 4h显著升高，但在3h无明显变化，而子宫OTRmRNA在1h后显著升高。正常大鼠动情前期与动情间期相比，动情前期VMH中OTRmRNA表达显著增加。结果表明，中枢催产素参与了大鼠摄食量和运动活动的调节，雌激素通过诱导催产素对雌性大鼠的催产素作用增强。这种雌激素诱导的OTR调节在子宫和VMH中都可以观察到，但由于OTRmRNA增加的幅度和潜伏期的不同，这两种机制对OTR的调节可能存在不同的修饰。较少

Oxytocin is a hormone which is produced in the paraventricular nucleus and the supraoptic nucleus of hypothalamus and secreted from the posterior pituitary, and has been reported to be also secreted in the brain and involved in the several brain functions. The aim of this study is to investigate the brain functions of oxytocin in feeding and locomotor activity in rats.First, the effects of oxytocin on neuropeptide-Y (NPY) and agouti-related protein (AgRP)-induced food intake were examined. In Wistar male rats oxytocin (1nmlo/5ul, icv) or saline were injected through the implanted cannula and 30 min later NPY, AgRP (1nmlo/5ul, icv) or saline were injected. After the second injection, food intake was monitored for 1 h and 2 h. Oxytocin did not affect the NPY- and AgRP-induced food intake, but significantly reduced the basal food intake in saline-treated rats.Next, the effects of oxytocin on the locomotor activity in Wistar male and female rats were examined. When oxytocin was injected in … More to the ventromedial hypothalamus (VMH) of intact male or ovariectomized (OVX) female rats, the locomoter activity monitored in the running wheel significantly increased. This effect of oxytocin in OVX rats was enhanced by the pretreatment with 17β-estradiol (E2). In OVX rats, oxytocin receptor (OTR) mRNA in VMH significantly increased 24 h after E2 treatment, but did not change at 3 h, while the uterine OTRmRNA significantly increased 1 h after the treatment. OTRmRNA in VMH increased on proestrus significantly compared with that on diestrus during the estrous cycle in intact rats. The change of OTRmRNA in VMH is small (about 2 folds) and delayed compared with that in uterus.These results suggested that the central oxytocin is involved in the regulation of food intake and locomotor activity in rats and that the effect of oxytocin in female rats is enhanced by estrogen through the induction of OTR. This estrogen-induced OTR regulation are observed both in uterus and VMH, but it is possible that there is a different modification in OTR regulation between two mechanisms because of the differences in the amplitude and latency of OTR mRNA increase. Less