Ghrelin mechanisms of food reward. Part 2. Interaction of ghrelin with hormones, neuropeptides and other endogenous ligands

The hunger hormone, ghrelin, is produced not only in response to food deprivation, but is also released during various types of stress. In recent years, the rise in ghrelin levels has come to be seen as an essential component of the stress response. The review is devoted to ghrelin-dependent mechanisms providing reciprocal interaction between the hypothalamuspituitaryadrenal cortex axis and the dopaminergic reward system. Direct and feedback links between the stress-realizing system of the paraventricular nucleus, the neural networks of the lateral hypothalamus and the arcuate nucleus (which form the centers of hunger/satiation), and the mesolimbic reward system are considered. The role of peripheral satiety hormones and glucocorticoids in the regulation of motivation and reinforcement is discussed, as well as the involvement of endogenous opioid and endocannabinoid receptors in the learning of dopaminergic neurons in the ventral tegmental area and the hippocampus.