The hypothalamus controls the feeding/appetite and energy expenditure in mammals. One region of the hypothalamus, the median eminence, which is a circumventricular organ, has unusual structural features. Fenestrated capillaries in the region have a vital role in allowing entry of peripheral signals into the brain. Peripheral hormones and nutrients from the blood stream can then be easily sensed and consequently regulated by the central nervous system. The blood brain barrier in the region is regulated by a particular glial cell, called tanycytes. Their cell bodies line the third ventricle, contact the cerebrospinal fluid, and project a single process towards hypothalamic nuclei, such as the arcuate, ventromedial and dorsomedial nuclei. Our laboratory recently demonstrate that tanycytes can directly sense glucose, artificial sweeteners and L-amino acids via activate specific receptors to induce Ca2+ waves in an ATP receptor-dependent manner. Changes in the tanycytic blood brain barrier were also observed according to peripheral signals. Tanycytes therefore can act as cellular integrators of macronutrient signals. An important question is whether these signals in tanycytes are also communicated to hypothalamic neurons? To demonstrate tanycyte-neuron communication we expressed a calcium permeable version of channelrhodopsin2 (CatCh) specifically in tanycytes and recorded from neurons of the arcuate neucleus, with patch clamp methods. Our data suggest, that optogenetic activation of tanycytes can excite a range of neurons in the arcuate nucleus. This suggests that tanycytes can convey information about the macronutrient status of an individual to the hypothamalic neural networks that control energy homeostasis. They must therefore be considered as an integral and important component of these neural networks.