“…For functional characterization of newly identified 5-HT 2C receptor agonists, functional data are nowadays generally based on measurements of a defined second messenger response, such as phosphoinositide hydrolysis or increase in intracellular calcium, at the human 5-HT 2C , 5-HT 2A , and 5-HT 2B receptors expressed in the same parental cell line, for example in CHO-K1 (Chinese hamster ovary K1) cells. 28,63 However, several other diverse functional models have been described in the literature for the pharmacological characterization of the 5-HT 2 receptor subtypes, that is, in vitro models (biochemical assays or tissue preparations) such as phosphoinositide hydrolysis in rat or pig choroid plexus (5-HT 2C ), [64][65][66] phosphoinositide hydrolysis in rat cortex (5-HT 2A ), 64 effect on human platelet aggregation (5-HT 2A ), 67 contraction of rat jugular vein (5-HT 2A ), 68 contraction of the isolated rat tail artery (5-HT 2A ), 69 and contraction of isolated rat stomach fundus muscle strips (5-HT 2B ), 70,71 as well as in vivo models such as head-twitch response in rodents (5-HT 2A ) 72 and penile erections in rats (5-HT 2C ). 73 However, comparisons of agonist potency and relative efficacy between studies may prove to be difficult; the data do not always reflect the literature in terms of absolute potency and relative efficacy.…”