RS 67333 hydrochloride

The effects of novel, selective 5-hydroxytryptamine (5-HT)4 receptor ligands in rat spatial navigation.[Pubmed:9225295]

Neuropharmacology. 1997 Apr-May;36(4-5):689-96.

Activation of central 5-hydroxytryptamine (5-HT4) receptors may enhance cognitive performance. In the present study, the effects of two novel, potent and selective 5-HT4 receptor agonists, RS 67333 (1-(4-amino-5-chloro-2-methoxyphenyl)-3-(1-n-burtl-4-piperidinyl)- 1-propanone) and RS 67506 (1-(4-amino- 5-chloro-2-methoxyphenyl)-3-[1-[2-[(methylsulfonyl)amino]ethyl]-4- piperidinyl]-1-propanone), were studied in a rat model of spatial learning and memory; the Morris water maze. RS 67333 (0.1, 10 and 1000 micrograms/kg, intraperitoneally (i.p.)), a highly potent, selective and hydrophobic 5-HT4 receptor agonist, reversed the decrements in cognitive performance induced by atropine (30 mg/kg, i.p.). By contrast, no effect was seen to RS 67506 (0.1, 10 and 1000 micrograms/kg, i.p.), a hydrophilic 5-HT4 receptor agonist, of equivalent potency and selectivity to RS 67333. This differential effect may reflect the enhanced ability of RS 67333 to enter the CNS, with respect to RS 67506. The ameliorative actions of RS 67333 on cognitive dysfunction were abolished by prior treatment with a selective 5-HT4 receptor antagonist, RS 67532 [1-(4-amino-5-chloro-2-(3, 5-dimethoxy benzyloxyphenyl)-5-(1-piperidinyl)-1-pentanone; 1 mg/kg, i.p.]. When given alone, or in naive rats, RS 67532 (0.1, 10 and 1000 micrograms/kg, i.p.), was without effect. None of the compounds tested affected the swim speed at any of the doses used. In separate locomotor studies, RS 67532 reduced activity at 1 and 10 mg/kg, i.p., although no effect was seen with RS 67333 or RS 67506 (0.01-10 mg/kg, i.p.). These data suggest that RS 67333 reversed the cognitive deficit induced by atropine and support a role of 5-HT4 receptors in rat spatial learning and memory.

Pharmacological characterization of two novel and potent 5-HT4 receptor agonists, RS 67333 and RS 67506, in vitro and in vivo.[Pubmed:8564196]

Br J Pharmacol. 1995 Aug;115(8):1387-92.

1. The pharmacology of two novel 5-HT4 receptor agonists, RS 67333 (1-(4-amino-5-chloro-2-methoxy-phenyl)-3-[1(n-butyl)-4-piperidinyl]-1- propanone HCl) and RS 67506 (1-(4-amino-5-chloro-2-methoxy-phenyl)-3-[1-(2-methyl sulphonylamino)ethyl-4-piperidinyl]-1-propanone HCl) have been assessed in vitro and in vivo. 2. RS 67333 and RS 67506 exhibited affinities (pKi = 8.7 and 8.8, respectively) for the 5-HT4 binding sites, labelled with [3H]-GR 113808, in guinea-pig striatum. The Hill coefficients from these displacement curves were not significantly different from unity. The compounds exhibited lower affinities (< 6.0) at several other receptors including 5-HT1A, 5-HT1D, 5-HT2A, 5-HT2C, dopamine D1, D2 and muscarinic M1-M3 receptors. However, RS 67333 and RS 67506 did exhibit affinities for the sigma 1 (pKi = 8.9 and 7.9, respectively) and sigma 2 (pKi = 8.0 and 7.3, respectively) binding sites. 3. At the 5-HT4 receptor mediating relaxation of the carbachol-precontracted oesophagus, RS 67333 and RS 67506 acted as potent (pEC50 8.4 and 8.6, respectively), partial agonists (intrinsic activities, with respect to 5-HT were 0.5 and 0.6, respectively) with respect to 5-HT. Relaxant responses to RS 67333 or RS 67506 were surmountably antagonized by GR 11308 (10 nM), with apparent affinities (pKB) of 9.1 and 9.0, respectively. RS 67333 and RS 67506 induced dose-dependent increases in heart rate of the anaesthetized micropig (ED50 4.9 and 5.4 micrograms kg-1, i.v.), with maximal increases of 35 and 47 beats min-1, respectively. 4. RS 67333 and RS 67506, therefore, acted as potent, partial 5-HT4 receptor agonists in vitro and in vivo. These compounds, by virtue of their high potency and selectivity, may have some utility in elucidating the physiological role of 5-HT4 receptors.

Central 5-HT4 receptors.[Pubmed:8578609]

Trends Pharmacol Sci. 1995 Nov;16(11):391-8.

Activation of the 5-HT4 receptor mediates widespread effects in central and peripheral nervous systems. Recent developments, such as the identification of novel, selective agonists and antagonists, as well the cloning of the receptor, have provided insights into the physiological role of the receptor. In this article, Richard Eglen and colleagues assess the emerging evidence relating to the function of the 5-HT4 receptor in the brain. The cerebral distribution of the receptor, along with neurochemical and electrophysiological data, suggests a role in cognition. The role of the receptor in modulation of dopamine transmission and anxiolysis is also addressed.