The influence of modifications in imide fragment structure on 5-HT(1A) and 5-HT(7) receptor affinity and in vivo pharmacological properties of some new 1-(m-trifluoromethylphenyl)piperazines.

New, flexible (7, 9, 11 and 13) and rigid (8, 10, 12 and 14) imides with a 1-(m-trifluorophenyl)piperazine fragment and a tetramethylene or a 1e,4e-cyclohexylene spacer, respectively, showed very high affinity (K(i)=0.3-34 nM) and agonistic in vivo activity for 5-HT(1A) receptors. Flexible new compounds and the previously described 5 also bound to 5-HT(7) receptors (K(i)=21-134 nM). Selected glutarimide derivatives, that is, the most potent postsynaptic 5-HT(1A) receptor agonist rigid compound 8 and its flexible analogue 7, as well as the previously described full agonist-rigid compound 6 and the partial agonist-its flexible counterpart 5 exhibited moderate affinity for alpha(1)-adrenoceptors (K(i)=85 - 268 nM), but were practically devoid of any affinity for dopamine D(2) sites. Those glutarimides demonstrated anxiolytic- (5 and 7) and antidepressant-like (5, 6 and 8) activity in the four-plate and the swim tests in mice, respectively; at the same time, however, they inhibited the locomotor activity of mice. The antidepressant-like effect of 8 was significantly stronger than that induced by imipramine used as a reference antidepressant.

Conformational restriction in novel NAN-190 and MP3022 analogs and their 5-HT(1A) receptor activity.

The newly synthesized analogs of NAN-190 containing m-Cl and m-CF(3) substituents in the arylpiperazine moiety and their conformationally restricted counterparts showed a very high 5-HT(1A )receptor affinity. In the LLR test, the flexible compounds 4a and 5a displayed features of a partial agonist and agonist, respectively. The conformational restriction in the tested structures caused alternations in the observed in vivo effects; compounds 4b and 5b were classified as an inactive agent and an antagonist of postsynaptic 5-HT(1A )receptors, respectively. Rigidification of MP3022 and its 5,6-dimethyl analog structures resulted in cis and trans stereoisomers 6b-9b with a 1- and 2-substituted benzotriazole moiety. In both series, in vitro experiments showed that the cis configurations of the compounds were better tolerated by 5-HT(1A) receptor sites than the trans ones. The conformational analysis revealed various spatial regions that can be explored by terminal benzotriazole fragments in those structures. Like the previously described cis-6b, the new ligand cis-7b, displayed features of a postsynaptic 5-HT(1A) receptor agonist, whereas cis-8b was characterized as a partial agonist of those receptor sites. It was suggested that the nonlinear geometry of the above agents has significant influence on the postsynaptic 5-HT(1A )receptor stimulation.

Synthesis and 5-HT(1A), 5-HT(2A) receptor activity of new beta-tetralonohydantoins.

A series of new 3-[4-(4-arylpiperazinyl)-butyl]-beta-tetralonohydantoins (8a-13a) were synthesized. The compounds exhibited high affinity for 5-HT(1A) receptors (K(i)=6 to 55 nM) combined with moderate-to-high 5-HT(2A) receptor affinities (K(i)=45 to 213 nM). The results of in vivo studies indicated that of the compounds tested, 3-[4-(4-phenylpiperazinyl)-butyl-beta-tetralonohydantoin (8a) showed features of full (pre- and postsynaptic) 5-HT(1A) receptor agonists, whereas compounds 9a-13a behaved like antagonists of postsynaptic 5-HT(1A) receptors; additionally, compound 13a produced an effect characteristic of presynaptic 5-HT(1A) receptor agonists. Moreover, compounds 8a and 10a-13a exhibited properties of 5-HT(2A) receptor antagonists. Due to the most interesting 5-HT(1A)/5-HT(2A) functional profile compounds 8a and 13a were further tested for their potential psychotropic activity. In fact, compound 8a (but not 13a) showed diazepam-like anxiolytic activity and behaved like a weak antidepressant.