HTR1F is a G-protein coupled receptor for 5-hydroxytryptamine (serotonin) that also functions as a receptor for various alkaloids and psychoactive substances. Ligand binding causes a conformation change that triggers signaling via guanine nucleotide-binding proteins (G proteins) and modulates the activity of down-stream effectors such as adenylate cyclase. Signaling inhibits adenylate cyclase activity. HTR1F has high expression in the isocortex and some expression in the olfactory bulb, hippocampus, trigeminal ganglia, and cerebral blood vessels in the brain. In peripheral tissues, it is found in the uterus, mesentery, and arteries. In immunohistochemistry of cancer, HTR1F may show faint positivity in breast cancer, non-small cell lung cancer, ovarian carcinomas, pancreatic carcinomas and glioblastomas. References: The Biochemical Basis of Neuropharmacology. 8th. Oxford, UK: Oxford University Press; 2003. pp. 271–320; Neurobiol Dis. 2005 Aug; 19(3):378-85, PMID: 16023580; Neuroscience. 2010 Aug 11; 169(1):229-35, PMID: 20423722; Neurol Res Int. 2017; 2017: 7138926, PMID: 28630769;