G-protein coupled receptor for 5-hydroxytryptamine (serotonin). Also functions as a receptor for various drugs and psychoactive substances, including ergot alkaloid derivatives, 1-2,5,-dimethoxy-4-iodophenyl-2-aminopropane (DOI) and lysergic acid diethylamide (LSD). Ligand binding causes a conformation change that triggers signaling via guanine nucleotide-binding proteins (G proteins) and modulates the activity of down-stream effectors. Beta-arrestin family members inhibit signaling via G proteins and mediate activation of alternative signaling pathways. Signaling activates a phosphatidylinositol-calcium second messenger system that modulates the activity of phosphatidylinositol 3-kinase and down-stream signaling cascades and promotes the release of Ca(2+) ions from intracellular stores. Regulates neuronal activity via the activation of short transient receptor potential calcium channels in the brain, and thereby modulates the activation of pro-opiomelacortin neurons and the release of CRH that then regulates the release of corticosterone. Plays a role in the regulation of appetite and feeding behavior, responses to anxiogenic stimuli and stress. Plays a role in insulin sensitivity and glucose homeostasis. Interacts with MPDZ. Interacts with ARRB2 (By similarity). Detected in brain cortex, hypothalamus, brainstem and arcuate nucleus. Detected in the paraventricular nucleus of the hypothalamus. The PDZ domain-binding motif is involved in the interaction with MPDZ. N-glycosylated. No obvious phenotype at birth, but mutant mice are prone to sudden death from seizures. When fed ad libitum, adult mice display higher body weight and increased adiposity compared to wild-type littermates. No difference in body weight is found when they receive the same amount of food as their wild-type littermates, indicating that the increased body weight is due to altered feeding behavior. Overweight older mice develop insulin resistance and impaired glucose tolerance. Young mice exhibit insulin resistance, but normal glucose tolerance, due to increased insulin levels in the blood. Insulin resistance is reversed when Htr2c expression is restored in pro-opiomelacortin neurons. Mutant mice display impaired activation of pro-opiomelacortin neurons in the paraventricular nucleus of the hypothalamus, leading to decreased release of CRH and corticosterone. Likewise, they exhibit blunted behavorial responses to anxiogenic environments and stress. Belongs to the G-protein coupled receptor 1 family.