Studies in several central effects of oxytocin in lactating rats

催产素是一种产生于下丘脑室旁核和视上核，由垂体后叶分泌的激素，据报道也在大脑中分泌，参与大脑的几种功能。本研究旨在探讨催产素在大鼠进食和运动活动中的脑功能。首先，研究了催产素对神经肽y （NPY）和针刺相关蛋白（AgRP）诱导的食物摄入的影响。Wistar雄性大鼠经植入导管注射催产素（1nmlo/5ul, icv）或生理盐水，30 min后注射NPY、AgRP （1nmlo/5ul, icv）或生理盐水。在第二次注射后，监测1 h和2 h的食物摄取量。催产素对NPY和agrp诱导的食物摄取量没有影响，但显著降低了盐处理大鼠的基础食物摄取量。研究了催产素对Wistar雄性和雌性大鼠运动活动的影响。在正常雄性或去卵巢雌性大鼠腹内侧下丘脑（VMH）注射催产素后，在跑步轮中监测到的运动活动显著增加。经17β-雌二醇（E2）预处理后，催产素对OVX大鼠的作用增强。在OVX大鼠中，E2处理24 h后VMH的催产素受体（OTR） mRNA显著升高，但在3 h时没有变化，而子宫OTRmRNA在处理1 h后显著升高。在正常大鼠发情周期中，VMH中OTRmRNA在发情前期较发情后期显著升高。与子宫相比，VMH中OTRmRNA的变化较小（约为2倍）且延迟。这些结果表明，中枢催产素参与调节大鼠的食物摄入和运动活动，雌性激素通过诱导OTR增强了催产素在雌性大鼠中的作用。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OTR mRNA增加的幅度和潜伏期的差异，两种机制之间的OTR调节可能存在不同的修改。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