BRL 46470A: a highly potent, selective and long acting 5-HT3 receptor antagonist with anxiolytic-like properties.
The novel 5-HT3 antagonist, BRL 46470A (endo-N-(8-methyl-8-azabicyclo [3.2.1]oct-3-yl)2,3-dihydro-3,3 dimethyl-indole-1-carboxamide, hydrochloride), has been investigated in a series of in vitro and in vivo tests, including the effect of the drug in models of anxiolysis. In classical tests for 5-HT3 receptor antagonism, BRL 46470A was shown to antagonise 5-HT3 mediated responses in the guinea-pig ileum [pA2 8.3 +/- 0.5, slope 0.98 +/- 0.20, mean +/- SEM (5)], the rabbit isolated heart (pA2 10.1 +/- 0.1, slope 1.2 +/- 0.2, n = 5) and the rat Bezold-Jarisch model (ID50 0.7 microgram/kg IV +/- 0.1, n = 8), with a long duration of action (> 3 h). BRL 46470A selectively displaced [3H]-BRL 43694 from 5-HT3 binding sites in rat brain membranes (Ki 0.32 nM +/- 0.04, n = 4) without displacing (at concentrations greater than 1 microM) a wide variety of ligands binding to other neurotransmitter receptors, opioid receptors and to neurotransmitter gated ion channel complexes. In vivo, BRL 46470A showed anxiolytic-like activity in two animal models predictive of antianxiety effects-elevated X-maze and social interaction in rats. In both models, BRL 46470A showed significant activity over a wide dose-range following both oral (0.0001-0.1 mg/kg PO) and systemic administration. The unique level of potency of BRL 46470A was apparent in the rat social interaction test and was shown to be 100 fold more potent than the 5-HT3 receptor antagonist ondansetron, with no evidence of a bell-shaped dose response curve over 4 orders of magnitude.(ABSTRACT TRUNCATED AT 250 WORDS)
Blackburn
T P
TP
SmithKline Beecham Pharmaceuticals, Harlow, Essex, UK.
Baxter
G S
GS
Kennett
G A
GA
King
F D
FD
Piper
D C
DC
Sanger
G J
GJ
Thomas
D R
DR
Upton
N
N
Wood
M D
MD
D000818:Animals; D014151:Anti-Anxiety Agents / Q000494:pharmacology*; D001643:Bridged Bicyclo Compounds / Q000494:pharmacology*; D019086:Bridged Bicyclo Compounds, Heterocyclic; D003975:Diazepam / Q000494:pharmacology; D004947:Esophagus / Q000187:drug effects; D006168:Guinea Pigs; D006321:Heart / Q000187:drug effects; D007082:Ileum / Q000187:drug effects; D066298:In Vitro Techniques; D007211:Indoles / Q000494:pharmacology*; D007398:Interpersonal Relations; D015640:Ion Channel Gating / Q000187:drug effects; D008297:Male; D017294:Ondansetron / Q000494:pharmacology; D017933:Peripheral Nervous System / Q000187:drug effects; D010879:Piperazines / Q000494:pharmacology; D011817:Rabbits; D011869:Radioligand Assay; D051381:Rats; D017207:Rats, Sprague-Dawley; D016194:Receptors, N-Methyl-D-Aspartate / Q000037:antagonists & inhibitors; D011985:Receptors, Serotonin / Q000187:drug effects*; D012018:Reflex / Q000187:drug effects; D012702:Serotonin Antagonists / Q000494:pharmacology*
D014151:Anti-Anxiety Agents; D001643:Bridged Bicyclo Compounds; D019086:Bridged Bicyclo Compounds, Heterocyclic; D007211:Indoles; D010879:Piperazines; D016194:Receptors, N-Methyl-D-Aspartate; D011985:Receptors, Serotonin; D012702:Serotonin Antagonists; C075685:BRL 46470; D017294:Ondansetron; C050592:3-(2-carboxypiperazin-4-yl)propyl-1-phosphonic acid; D003975:Diazepam