HTR5A (5-HT5a, 5-hydroxytryptamine serotonin receptor 5A) is a multi-pass membrane receptor for serotonin that negatively regulates adenylate cyclase. It is relevant to psychiatric diseases that involve serotonin and may be important for mood regulation and disorder. Furthermore, both blocking and promoting expression of HTR5A impact short- and long-term memory and it is considered to be a potential therapy target for schizophrenia and memory deficit disorders. HTR5A agonists include valerenic acid, olanzapine and lysergic acid diethylamide, while antagonists include risperidone, latrepirdine, AS-2674723, AS-2030680, ASP-5736 and SB-699,551. In immunohistochemistry, HTR5A has membranous positivity in the cerebellum, cortex, hippocampus, nucleus accumbens, hypothalamus and amygdala in the brain, and is also positive at low levels in the gastrointestinal tract, thyroid, lung, pancreas, skin, appendix, breast and adrenal gland. References: J Pharmacol Sci. 2015 Mar;127(3):362-9, PMID: 25837935; Mol Neurodegener. 2008 Oct 21;3:15, PMID: 18939977; Brain Research. Molecular Brain Research. 138 (2): 191–7, PMID: 15921820; European Journal of Pharmacology. 361 (2–3): 299–309, PMID: 9865521; J Neurosci. 2012 Apr 25;32(17):5804-9, PMID: 22539842;