数据采集传输系统:求助翻译高手!!

Implicitinthishypothesisisthesuggestionthatbrainareasinnervated by arcuate nucleus neurons are sites where second-order neurons involved in the energy homeostasis circuit are located. But theidentificationofsuch downstreamneuronsisjustbeginning,and energy homeostasis probably involves integrated and redundant pathways, rather than a discrete set of neurons connected in series to oneanother.Modelsforunderstandinghowarcuatenucleusneurons ultimately affect food intake nonetheless provide a useful framework for future study. One possible model is proposed below. Model for second-order neuronal signalling pathways Hypothalamic areas including the paraventricular nucleus (PVN), zona incerta, perifornical area (PFA) and LHA are richly supplied by axons from arcuate nucleus NPY/AGRP and POMC/CART neurons74,75. Insight into the role in energy homeostasis played by neurons in these areas can be gleaned from earlier stimulation and lesioning studies. For example, PVN stimulation inhibits food intake, whereas the reverse is true of stimulation of the LHA50 and adjacent PFA76. Conversely, bilateral PVN lesions cause a hyperphagic obesity syndrome, whereas bilateral lesioning of the LHA causes anorexia and weight loss50,64. These observations indicate that anorexigenic and orexigenic signalling molecules might be synthesized in the PVN and LHA, respectively (Fig. 5). Consistent with these predictions, several neuropeptides synthesized in PVN neurons reduce food intake and body weight when administered centrally. These include CRH, which causes anorexia and also activates the sympathetic nervous system in addition to its role as a major regulator of the hypothalamic–pituitary–adrenal axis50,77; TRH, which reduces food intake51 in addition to stimulating the thyroid axis; and oxytocin, which reduces food intake in addition to regulating uterine function78. If these PVN neurons are secondorder catabolic effectors located downstream of the arcuate nucleus, they should be stimulated by melanocortin and/or CART signalling, but inhibited by NPY signalling, and further study is warranted to test this prediction. The hypothesis that second-order neurons involved in anabolic signalling reside within the LHA/PFA is supported by studies of MCH, an orexigenic peptide located in this brain area79.