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1.
Neuropharmacology ; 41(2): 186-99, 2001 Aug.
Article in English | MEDLINE | ID: mdl-11489455

ABSTRACT

SB-243213 (5-methyl-1-[[-2-[(2-methyl-3-pyridyl)oxy]-5-pyridyl]carbamoyl]-6-trifluoromethylindoline hydrochloride) is a new, selective 5-hydroxytryptamine (5-HT)2C receptor inverse agonist. SB-243213 has high affinity for the human 5-HT2C receptor (pK(i) 9.37) and greater than a 100-fold selectivity over a wide range of neurotransmitter receptors, enzymes and ion channels. In in vitro functional studies, SB-243213 acted as an inverse agonist at the human 5-HT2C receptor with a pK(b) of 9.8. In in vivo studies, SB-243213 was a potent inhibitor of central 5-HT2C receptor-mediated function in rats, blocking meta-chlorophenylpiperazine-induced hypolocomotion with an ID50 of 1.1 mg/kg p.o. and a long duration of action (>8 h). In rats, SB-243213 exhibited anxiolytic-like activity in both the social interaction and Geller-Seifter conflict tests. Importantly, unlike diazepam, chronic administration of SB-243213 did not result in the development of either tolerance to the anxiolytic-like effects or withdrawal anxiogenesis. Furthermore, in rodents, SB-243213 did not affect seizure threshold, did not increase body weight or induce catalepsy, but attenuated the haloperidol-induced catalepsy. SB-243213 did not affect amphetamine-, MK-801- or phencyclidine-induced hyperactivity. In conclusion, SB-243213 may possess an improved anxiolytic profile compared to benzodiazepines. SB-243213 also modulates dopaminergic transmission, lacks pro-psychotic properties and may have utility in the treatment of schizophrenia and motor disorders.


Subject(s)
Anti-Anxiety Agents/pharmacology , Indoles/pharmacology , Motor Activity/drug effects , Pyridines/pharmacology , Receptors, Serotonin , Social Behavior , Animals , Anti-Anxiety Agents/adverse effects , Anti-Anxiety Agents/therapeutic use , Anxiety/drug therapy , Anxiety/psychology , Catalepsy/chemically induced , Catalepsy/drug therapy , Diazepam/adverse effects , Dose-Response Relationship, Drug , Drug Tolerance/physiology , Humans , Indoles/therapeutic use , Inositol Phosphates/metabolism , Male , Motor Activity/physiology , Pyridines/therapeutic use , Rats , Rats, Sprague-Dawley , Receptor, Serotonin, 5-HT2C , Receptors, Serotonin/metabolism , Substance Withdrawal Syndrome/drug therapy , Substance Withdrawal Syndrome/psychology
2.
Br J Pharmacol ; 131(6): 1050-4, 2000 Nov.
Article in English | MEDLINE | ID: mdl-11082110

ABSTRACT

1. The aim of this study was to characterize the pharmacological profile of the GABA(B1)/GABA(B2) heterodimeric receptor expressed in Chinese hamster ovary (CHO) cells. We have compared receptor binding affinity and functional activity for a series of agonists and antagonists. 2. The chimeric G-protein, G(qi5), was used to couple receptor activation to increases in intracellular calcium for functional studies on the Fluorimetric Imaging Plate Reader (FLIPR), using a stable GABA(B1)/GABA(B2)/G(qi5) CHO cell line. [(3)H]-CGP-54626 was used in radioligand binding studies in membranes prepared from the same cell line. 3. The pharmacological profile of the recombinant GABA(B1/B2) receptor was consistent with that of native GABA(B) receptors in that it was activated by GABA and baclofen and inhibited by CGP-54626A and SCH 50911. 4. Unlike native receptors, the GABA(B1)/GABA(B2)/G(qi5) response was not inhibited by high microMolar concentration of phaclofen, saclofen or CGP 35348. 5. This raises the possibility that the GABA(B1)/GABA(B2)/G(qi5) recombinant receptor may represent the previously described GABA(B) receptor subtype which is relatively resistant to inhibition by phaclofen.


Subject(s)
Baclofen/analogs & derivatives , GABA Agonists/metabolism , GABA Antagonists/metabolism , Receptors, GABA-B/metabolism , Receptors, GABA/metabolism , Animals , Baclofen/metabolism , Baclofen/pharmacology , CHO Cells , Cricetinae , Dose-Response Relationship, Drug , GABA Antagonists/pharmacology , Humans , gamma-Aminobutyric Acid/metabolism
3.
J Pharm Pharmacol ; 51(3): 319-30, 1999 Mar.
Article in English | MEDLINE | ID: mdl-10344634

ABSTRACT

A series of simple O-acylated derivatives of the naturally occurring clavine alkaloids lysergol and dihydrolysergol-I were synthesized and tested in-vitro for their ability to interact with 5-HT2A receptors in rat tail artery, 5-HT2C receptors in piglet choroid plexus, 5-HT1B receptors in guinea-pig iliac artery and alpha1-adrenergic receptors in rat aorta. In contrast to the classical ergoline 5-HT2A receptor antagonists methysergide and LY53857, the compounds produced competitive antagonism of the 5-HT response in rat tail artery. Affinities of ergolines 3-14 were higher (pA2 values of 7.33-8.40) than those of the parent alcohols lysergol (1) and dihydrolysergol-I (2), respectively. The introduction of an isopropyl substituent at the N(1) position of the compounds failed to enhance 5-HT2A receptor affinity. Compounds 3-14 exhibited lower affinities for alpha1-adrenergic receptors than for 5-HT2A receptors. In particular, those lysergol derivatives that had an isopropyl substituent at the N(1) position were highly specific 5-HT2A receptor antagonists (ratio 5-HT2A/alpha1 = 302-3548). Selected derivatives of lysergol (3-5, 9-11) which were assayed for radioligand binding at 5-HT2C receptors in piglet choroid plexus had affinities that were similar to those found in rat tail artery. Additionally, lysergol and its N(1)-unsubstituted derivatives were found to be partial agonists (alpha of 0.2-0.4) for 5-HT2C receptor-mediated inositol phosphate accumulation in piglet choroid plexus. On the other hand, analogues with an isopropyl substituent at N(1) showed no measurable agonist activity. The observation that N(1)-unsubstituted derivatives of lysergol possessed agonist properties at 5-HT2C receptors whereas their agonist activity at 5-HT2A receptors was marginal (alpha of 0.05 for compound 3 at 1 microM) or not measurable, suggests that these compounds have different abilities to cause conformational change at the two receptor types. Selected derivatives of lysergol (3-5, 9-11) which were examined as ligands for 5-HT1B receptors in guinea-pig iliac artery caused insurmountable blockade of the contractile effect of 5-HT. N(1)-isopropyl derivatives had 30-50-fold lower affinities for 5-HT1B receptors of this tissue than their N(1)-unsubstituted analogues. It is concluded that O-acylated derivatives of the clavine alkaloids lysergol and dihydrolysergol-I mimic therapeutically relevant ergolines due to the complexity of their pharmacological profile as partial agonists and antagonists at 5-HT2A, 5-HT2C and 5-HT1B receptors, and at alpha1-adrenergic receptors.


Subject(s)
Arteries/drug effects , Ergolines , Receptors, Adrenergic, alpha-1/drug effects , Serotonin Antagonists/pharmacology , Animals , Antipsychotic Agents/pharmacology , Binding, Competitive , Ergolines/chemical synthesis , Ergolines/pharmacology , In Vitro Techniques , Inositol Phosphates/metabolism , Male , Rats , Rats, Wistar , Serotonin Receptor Agonists/pharmacology , Structure-Activity Relationship
4.
Neuroreport ; 7(9): 1457-60, 1996 Jun 17.
Article in English | MEDLINE | ID: mdl-8856697

ABSTRACT

The behavioural effects of m-chlorophenylpiperazine (mCPP) in rats and its clinical effects in man are thought to be related to its action at 5-HT2B/2C receptors. However, although mCPP is a partial agonist at these subtypes in rat, its efficacy at human 5-HT2B/2C receptors is unknown. We therefore investigated the activity of mCPP at cloned human 5-HT2B and 5-HT2C receptors. mCPP was a partial agonist at the human 5-HT2C receptor but antagonized the human 5-HT2B receptor. Therefore, while supporting the proposal that at least some of the clinical effects of mCPP are likely to be mediated via stimulation of the 5-HT2C receptor, this study also suggests that any 5-HT2B receptor-mediated effects are more likely to result from receptor blockade than from receptor activation.


Subject(s)
Kidney/drug effects , Piperazines/pharmacology , Serotonin Antagonists/pharmacology , Animals , Cell Line , Cloning, Molecular , Humans , Kidney/cytology , Kidney/embryology , Logistic Models , Rats , Serotonin Receptor Agonists/pharmacology
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