Uses
RS 67506 Hydrochloride is a novel and potent 5-HT4 receptor agonist.
Definition
ChEBI: A hydrochloride salt obtained by mixing equimolar amounts of RS 39604 with hydrochloric acid. A potent and selective 5-HT4 antagonist, with a pKi of 9.1 at 5-HT4 receptors in guinea pig striatal membranes and greater than 1000-fold selectivity over 5-HT1A,
2C, 3 and D1, D2, M1, M2, AT1, B1 and alpha1C receptors. The ketone group gives RS 39604 a relatively long half life; it is also orally active and so suitable for in vivo studies.
Biological Activity
A potent and selective 5-HT 4 partial agonist, with a pK i of 8.8 at 5-HT 4 sites in guinea pig striatum, but < 6.0 at several other receptors including 5-HT 1A, 1D, 2A, 2C , D 1 , D 2 and M 1-3 . It is active in vivo and has an intrinsic activity compared to 5-HT of 0.6.
in vitro
rs 67506 acted as a potent partial agonist with respect to 5-ht at the 5-ht4 receptor regulating relaxation of the carbachol-precontracted oesophagus. relaxant responses to rs 67506 was surmountably antagonized with apparent affinities (pkb) of 9.0. rs 67506, therefore, acted as potent, partial 5-ht4 receptor agonists in vitro. the compound may have been used in elucidating the physiological role in 5-ht4 receptors by virtue of their high potency and selectivity [1].
in vivo
rs 67506 induced dose-dependent potentiates heart rate of the anaesthetized micropig (ed50 5.4 pg kg-1, i.v.) with maximal increases of 47 beats min-1 [1]. in addition, in a rat model of spatial learning and memory, the effects of two novel potent and selective 5-ht4 receptor agonists (rs67333 and rs67506) were studied. by contrast, there was no effect seen to rs67506 (0.1, 10 and 1000 pg/kg, i.p.) of equivalent potency and selectivity to rs67333.this differential result may suggest the enhanced ability of rs67333 to enter the cns, with respect to rs67506 [2].
References
[1]. eglen rm, bonhaus dw, johnson lg, leung e, clark rd. pharmacological characterization of two novel and potent 5-ht4 receptor agonists, rs 67333 and rs 67506, in vitro and in vivo. br j pharmacol. 1995 aug;115(8):1387-92.
[2]. fontana dj, daniels se, wong eh, clark rd, eglen rm. the effects of novel, selective 5-hydroxytryptamine (5-ht) 4 receptor ligands in rat spatial navigation. neuropharmacology. 1997 apr-may;36(4-5):689-96.
