Decades ago, pioneering studies in cats and rodents identified regions within an ancient part of the brain, the hypothalamus, that are sufficient to increase or reduce appetite. Stimulating lateral parts of the hypothalamus was shown to promote feeding, whereas activating ventromedial regions reduced food consumption; these were described as hunger and satiety centers, respectively. In eLife this week, Caroline Wee and Erin Song (Engert and Kunes labs) report that lateral and medial hypothalamic circuits in the larval zebrafish, while sharing parallel functions with mammals, may in fact have more complex and dynamic roles in the control of energy homeostasis.
Similar to mammals, the larval zebrafish is able to regulate its feeding behavior based on its energy needs, largely due to the presence of conserved hypothalamic circuits. Using brain-wide activity mapping, Wee, Song et al. identified two major hypothalamic loci that were differentially regulated in voraciously-feeding fish (i.e. hungry fish presented with food), as compared to satiated fish. The lateral hypothalamus (LH), which shares homology with its mammalian counterpart, was highly active in voraciously-feeding fish, whereas a more ventromedially-situated region, the caudal hypothalamus (cH), had very low activity.
