SR 57227 hydrochloride

5-HT3-like receptors in the rat medial prefrontal cortex: further pharmacological characterization.[Pubmed:8891244]

Brain Res. 1996 Sep 9;733(1):21-30.

The aim of the study was to further characterize the pharmacological properties of 5-hydroxytryptamine (5-HT)3-like receptors in the rat medial prefrontal cortex (mPFC) using combinations of biochemical and electrophysiological approaches. Phenylbiguanide (PBG) and three chlorinated derivatives, ortho-chloro-PBG (oCPBG), meta-chloro-PBG (mCPBG) and para-chloro-PBG (pCPBG), dose-dependently stimulated phosphoionositide (PI) turnover in fronto-cingulate cortical slices. All three chloro-isomers of PBG were equipotent in stimulating PI turnover. SR 57227A ((4-amino)-(6-chloro-2-pyridyl) L-piperidine hydrochloride, a novel compound with high affinity and selectivity for peripheral and central 5-HT3 receptors) dose-dependently stimulated PI turnover in fronto-cingulate cortical slices. The rank order of potency of all the 5-HT3 receptor agonists tested in the PI assay as compared to 5-HT was: 5-HT > 2-Me-5-HT > SR57227A > PBG = mCPBG = oCPBG = mCPBG. 5-HT and 5-HT receptor agonists depressed the firing rate of both spontaneously active and glutamate-activated quiescent mPFC cells in a current (dose)-dependent fashion. The rank order of effectiveness of these compounds was: 5-HT > SR57227A = 2-Me-5-HT = mCPBG = oCPBG = pCPBG = PBG. Unlike its action on the 5-HT3 receptors in the periphery or cultured cell lines, D-tubocurarine chloride appears to be non-specific in blocking the depressant action of 2-Me-5-HT, gamma-aminobutyric acid and dopamine. Our results combined support the view that the pharmacological properties of 5-HT3-like receptors in the mPFC are not identical to those located in peripheral tissues and in cultured cell lines.

SR 57227A: a potent and selective agonist at central and peripheral 5-HT3 receptors in vitro and in vivo.[Pubmed:7689975]

Eur J Pharmacol. 1993 Jun 24;237(2-3):299-309.

SR 57227A (4-amino-(6-chloro-2-pyridyl)-1 piperidine hydrochloride) is a novel compound with high affinity and selectivity for the 5-HT3 receptor. The compound had affinities (IC50) varying between 2.8 and 250 nM for 5-HT3 receptor binding sites in rat cortical membranes and on whole NG 108-15 cells or their membranes in vitro, assayed under various conditions with [3H]S-zacopride or [3H]granisetron as radioligand. Like reference 5-HT3 receptor agonists, SR 57227A stimulated the uptake of [14C]guanidinium into NG 108-15 cells in the presence of substance P (EC50 = 208 +/- 16 nM) and contracted the isolated guinea-pig ileum (EC50 = 11.2 +/- 1.1 microM), effects that were antagonised by the 5-HT3 receptor antagonist tropisetron. The agonist effect of SR 57227A was also observed in vivo, as the compound elicited the Bezold-Jarisch reflex in anesthetised rats (ED50 = 8.3 micrograms/kg i.v.), an effect that was blocked by tropisetron and R,S-zacopride, but not by methysergide. When injected unilaterally into the mouse striatum, SR 57227A, like 2-methyl-5-HT, elicited contralateral turning behaviour which was antagonised by ondansetron. Furthermore, microiontophoretic application of SR 57227A markedly inhibited the firing rate of rat cortical neurones, an effect antagonised by tropisetron. Finally, in contrast to reference 5-HT3 agonists, SR 57227A bound to 5-HT3 receptors on mouse cortical membranes after systemic administration (ED50 = 0.39 mg/kg i.p. and 0.85 mg/kg p.o.). These results suggest that SR 57227A is a potent agonist at peripheral and central 5-HT3 receptors, both in vitro and in vivo. In view of the dearth of 5-HT3 receptor agonists which are capable of crossing the blood-brain barrier, SR 57227A may be useful in the characterisation of the neuropharmacological effects produced by the stimulation of these receptors.