trans-4-[4-(Methoxyphenyl)cyclohexyl]-1-arylpiperazines: a new class of potent and selective 5-HT(1A) receptor ligands as conformationally constrained analogues of 4-[3-(5-methoxy-1,2,3,4-tetrahydronaphthalen-1-yl)propyl]-1-arylpiperazines.
The present paper concerns the influence of conformational parameters on the recognition by rat 5-HT1A receptors of derivatives 4-[3-(5-methoxy-1,2,3,4-tetrahydronaphthalen-1-yl)propyl]-1-(2-pyridinyl)piperazine (1a) and 3-(5-methoxy-1,2,3,4-tetrahydronaphthalen-1-yl)-N-[2-(2-pyridyloxy)ethyl]propanamine (3b), two highly potent and selective 5-HT1A receptor ligands. Fifteen corresponding flexible and rigid analogues were prepared following several synthetic routes and were tested in binding assays with radioligands at 5-HT1A, D2, and alpha1 receptors from rat brain membranes. Among the new derivatives emerged trans-4-[4-(3-methoxyphenyl)cyclohexyl]-1-(2-pyridinyl)piperazine (trans-8a) and trans-N-[4-(3-methoxyphenyl)cyclohexyl]-2-(2-pyridyloxy)ethylamine (trans-8b). These compounds can be considered as conformationally constrained analogues of compounds 1a and 3a, respectively. In fact, compounds trans-8a and trans-8b showed a marked enhancement in 5-HT1A receptor affinity when compared to the corresponding cis isomers. Because compound trans-8a was a potent and selective 5-HT1A ligand (K(i), nM: 5-HT1A = 0.028, D2 = 2194, alpha1 = 767), it was chosen as a lead to prepare other analogues that were tested at 5-HT1A, D2, and alpha1 receptors from rat brain membranes, showing high affinity at the 5-HT1A and selectivity vs D2 and alpha1 receptors. Selected compounds were tested for their affinity at the human cloned 5-HT1A, alpha1a, alpha1b, alpha1d receptor subtypes. They were also submitted to the [35S]GTPgammaS binding assay stimulating the 5-HT1A receptor-mediated G-protein activation, therefore behaving as full or as partial agonists. Finally, the ability of iv administration of trans-8a to induce fore-paw treading in rats was evaluated in comparison with 8-OH-DPAT. Although the affinity (K(i)) and in vitro activity (pD'2) of trans-8a at the 5-HT1A receptor were higher than those of 8-OH-DPAT, the compound was less potent than the reference standard in inducing the symptom.
Perrone
R
R
Dipartimento Farmaco-Chimico, Università Bari, Italy. perrone@farmchim.uniba.it
Berardi
F
F
Colabufo
N A
NA
Leopoldo
M
M
Lacivita
E
E
Tortorella
V
V
Leonardi
A
A
Poggesi
E
E
Testa
R
R
D000818:Animals; D001921:Brain / Q000378:metabolism; D005021:Ethylamines / Q000138:chemical synthesis* / Q000737:chemistry / Q000378:metabolism; D016244:Guanosine 5'-O-(3-Thiotriphosphate) / Q000378:metabolism; D006367:HeLa Cells; D006801:Humans; D066298:In Vitro Techniques; D008024:Ligands; D008968:Molecular Conformation; D010879:Piperazines / Q000138:chemical synthesis* / Q000737:chemistry / Q000378:metabolism; D011725:Pyridines / Q000138:chemical synthesis* / Q000737:chemistry / Q000378:metabolism; D011869:Radioligand Assay; D051381:Rats; D018340:Receptors, Adrenergic, alpha-1 / Q000378:metabolism; D017448:Receptors, Dopamine D2 / Q000378:metabolism; D011985:Receptors, Serotonin / Q000187:drug effects* / Q000378:metabolism; D044263:Receptors, Serotonin, 5-HT1; D017366:Serotonin Receptor Agonists / Q000138:chemical synthesis* / Q000737:chemistry / Q000378:metabolism; D013237:Stereoisomerism; D013329:Structure-Activity Relationship; D014162:Transfection
C442804:4-(4-(3-methoxyphenyl)cyclohexyl)-1-(2-pyridinyl)piperazine; D005021:Ethylamines; D008024:Ligands; C442805:N-(4-(3-methoxyphenyl)cyclohexyl)-2-(2-pyridyloxy)ethylamine; D010879:Piperazines; D011725:Pyridines; D018340:Receptors, Adrenergic, alpha-1; D017448:Receptors, Dopamine D2; D011985:Receptors, Serotonin; D044263:Receptors, Serotonin, 5-HT1; D017366:Serotonin Receptor Agonists; D016244:Guanosine 5'-O-(3-Thiotriphosphate)