Effects of the serotonin 5-HT2A/2C receptor agonist DOI and of the selective 5-HT2A or 5-HT2C receptor antagonists EMD 281014 and SB-243213, respectively, on sleep and waking in the rat

The effects of the serotonin 5-HT(2A/2C) receptor agonist 1-(2,5-dimethoxy-4-iodophenyl)-2-aminopropane (DOI) and of the selective 5-HT(2A) or 5-HT(2C) receptor antagonists 7-{4-[2-(4-fluoro-phenyl)-ethyl]-piperazine-1-carbonyl}-1H-indole-3-carbonitrile HCl (EMD 281014) and 5-methyl-1-[[-2-[(2-methyl-3-pyridyl)oxy]-5-pyridyl]carbamoyl]-6-trifluoromethylindoline HCl (SB-243213), respectively, on spontaneous sleep were studied in adult rats implanted for chronic sleep recordings. Subcutaneous administration of DOI (0.35-0.7 mmol/kg) significantly increased waking and light sleep and reduced slow wave sleep, rapid-eye-movement (REM) sleep, and the number of REM periods. With subcutaneous EMD 281014 (1.2-4.8 mmol/kg) or SB-243213 (1.2-4.8 mmol/kg) a significant reduction in time spent in REM sleep was also seen. Pretreatment with EMD 281014 prevented the DOI-induced increase of waking and light sleep and the reduction of slow wave sleep. However, REM sleep remained suppressed. SB-243213 failed to reverse the changes of sleep and waking induced by DOI. Thus, on the basis of these results it appears that serotonin 5-HT(2A) receptor mechanisms might be responsible for the DOI-induced effects on waking and slow wave sleep.     

Prophylactic and therapeutic effects of acute systemic injections of EMD 281014, a selective serotonin 2A receptor antagonist on anxiety induced by predator stress in rats

We examined the effect of the selective serotonin 2A (5-HT(2A)) receptor antagonist 7-[4-[2-(4-fluoro-phenyl)-ethyl]-piperazine-1-carbonyl]-1H-indole-3-carbon itrile HCl (EMD 281014) [Bartoszyk, G.D., van Amsterdam, C., Bottcher, H., Seyfried, C.A., 2003. EMD 281014, a new selective serotonin 5-HT2A receptor antagonist. Eur. J. Pharmacol. 473, 229-230.] on change in affect following predator stress. Predator stress involved a 5 min unprotected exposure of rats to a domestic cat. Behavioral effects of stress were evaluated with hole board, plus maze, light/dark box and acoustic startle tests 1 week after stress. Predator stress increased anxiety-like behavior in the plus maze, light/dark box, and elevated response to acoustic startle. EMD 281014 (0.001, 0.01, 0.1, 1 or 10 mg/kg) and vehicle injection (ip) occurred either 10 min after predator stress (prophylactic testing), or 90 min prior to behavioral testing for the effects of predator stress (therapeutic testing 1 week after predator stress). In prophylactic testing, EMD 281014 prevented stress potentiation of startle in a dose dependent manner, though the most effective doses were midrange (0.01 and 0.1 mg/kg). Prophylactic administration of EMD 281014 also prevented stress-induced increase of open arm avoidance in the plus maze in a clear dose dependent manner (from 0.01 mg/kg onward). In therapeutic testing, EMD 281014 had no clear drug dependent effects on stress elevation of startle or on behavior of stressed rats in the elevated plus maze. Finally, EMD 281014 did not block the effects of stress on behavior in the light/dark box when given prophylactically or therapeutically. Findings implicate 5-HT(2A) receptors in initiation of some but not all lasting changes in anxiety-like behavior following predator stress. Potential clinical significance of findings are discussed.     

Effect of selective serotonin (5-HT) agonists and 5-HT2 antagonist on prolactin secretion

The present study was undertaken to determine the involvement of serotonergic 5-HT1 and 5-HT2 receptor subtypes in stimulation of the secretion of prolactin. Several 5-HT agonists were administered, in a dose-response fashion, to conscious rats and the effect on the levels of prolactin in plasma was measured. The 5-HT1A + 5-HT1B agonist RU 24969 (5-methoxy-3[1,2,3,6-tetrahydropyridin-4-yl]-1H-indole succinate) and the 5-HT1 + 5-HT2 agonist MK-212 (6-chloro-2-[1-piperazinyl]pirazine) increased levels of prolactin in plasma in a dose-dependent manner. In contrast, the selective 5-HT1A agonists 8-OH-DPAT (8-hydroxy-2-[di-n-propylamino]tetralin) and ipsapirone (2-[4-[4-(2-pyrimidinyl)-1-piperazinyl]butyl]-1,2-benzisothiazol-3 -(2H) one-1,1-dioxidehydrochloride) did not increase levels of prolactin in plasma at any dose. The 5-HT-releasing drug, fenfluramine, also increased the concentration of prolactin in plasma. Pretreatment with the selective 5-HT2 antagonist, LY53857 (6-methyl-1-[1-methylethyl]ergoline-8-carboxylic acid, 2-hydroxy-1-methyl propyl ester (Z)-2-butenedioate [1:1]), did not significantly diminish an increase in levels of prolactin in plasma, induced by injection of fenfluramine. The antagonist LY53857 inhibited, but did not block the MK-212- and RU 24969-induced increase in the levels of prolactin in plasma. By deduction, these data suggest that 5-HT1B receptors, or as yet undefined 5-HT receptor subtypes may be involved in the stimulation of the secretion of prolactin by endogenously released 5-HT, and that 5-HT2 receptors may play a minor role in the serotonergic regulation of the secretion of prolactin.     

Inverse agonist activity of sarpogrelate, a selective 5-HT2A-receptor antagonist, at the constitutively active human 5-HT2A receptor

Mutations producing constitutively active G-protein coupled receptors have been found in the pathophysiology of several diseases, implying that inverse agonists at the constitutively active receptors may have preferred therapeutic applications. Because of the involvement of 5-HT(2A) receptors in mediating many cardiovascular diseases, constitutively active mutants of the 5-HT(2A) receptor may be responsible for the disease states. Thus, the purpose of the present study was to investigate the inverse agonist activity of sarpogrelate, a selective 5-HT(2A)-receptor antagonist, and its active metabolite, M-1; and we compared their activities with those of other 5-HT(2A)-receptor antagonists such as ritanserin, ketanserin, and cyproheptadine. Using a constitutively active mutant (C322K) of the human 5-HT(2A) receptor, we demonstrated that like other 5-HT(2A)-receptor antagonists, sarpogrelate acts as a potent inverse agonist by significantly reducing basal inositol phosphate levels. However, there were no significant differences between sarpogrelate and other 5-HT(2A)-receptor antagonists for their inverse agonist activity. Compared with the wild type receptor, mutant receptor displayed significantly higher affinity for 5-HT and lower affinity for sarpogrelate. These results indicate that stabilization of the inactive conformation of the 5-HT(2A) receptor may be a key component of the mechanism of action of sarpogrelate.     

The antiemetic profile of Y-25130, a new selective 5-HT3 receptor antagonist.

Y-25130( (+/-)N-(1-azabicyclo[2.2.2]oct-3-yl)-6-chloro-4-methyl-3-oxo-3,4-dihydro - 2H-1,4-benzoxazine-8-carboxamide hydrochloride) is a potent and selective 5-HT3 receptor antagonist free of dopamine receptor blocking activity. This compound was effective against emesis induced in animals by cytotoxic drugs or by total body X-radiation. When given prophylactically, the doses required to completely inhibit cisplatin-induced emesis in dogs and doxorubicin and cyclophosphamide-induced emesis in ferrets were 0.1 and 0.3 mg/kg i.v., respectively. Y-25130, at the dose of 0.3 mg/kg i.v., almost completely inhibited X-radiation-induced emesis in ferrets. When given during emesis, the doses required to completely inhibit cisplatin-induced emesis in dogs and doxorubicin- and cyclophosphamide-induced emesis in ferrets were 0.1 and 0.3 mg/kg i.v., respectively. The i.v. dose of 0.3 mg/kg of Y-25130 was enough to almost completely inhibit cisplatin-induced emesis in dogs for 24 h. From these results, it is suggested that Y-25130 may become an effective antiemetic drug against emesis induced by anticancer therapy.     

Selective serotonin 5-HT<Subscript>2A</Subscript> receptor antagonist EMD 281014 improves delayed matching performance in young and aged rhesus monkeys

Rationale The superior cognitive effects of atypical neuroleptics over typical agents reported in the schizophrenia literature are often attributed to the more prominent antagonist activity of the atypical drugs at serotonin 5HT_2A receptors. However, atypical neuroleptics also have activity at many additional neurotransmitter receptors and few studies have specifically (and prospectively) tested the hypothesis that 5HT_2A antagonism alone results in enhanced cognitive function.Objectives The purpose of this study was to evaluate the selective 5-HT_2A antagonist, 7-{4-[2-(4-fluoro-phenyl)-ethyl]-piperazine-1-carbonyl}-1H-indole-3-carbonitrile HCl (EMD 281014) in young and aged monkeys in a test designed to assess working memory function.Methods Four oral doses (0.1, 1.0, 3.0, and 10.0 mg/kg) of EMD 281014 were evaluated in six young adult (mean age=9.2 years) and eight aged rhesus macaques (mean age=24.9 years) trained to perform a computer-assisted delayed matching-to-sample (DMTS) task.Results Depending on dose, EMD 281014 improved DMTS accuracy in young and aged monkeys primarily at either the medium or long retention intervals. While the latencies associated with incorrect color selections (choices latencies) tended to be longer than those associated with correct selections (particularly in the aged subjects) under baseline conditions, there were no significant effects of EMD 281014 on either sample or choice latencies in either age group. In addition, no adverse effects were observed across the range of doses evaluated in either cohort of animals.Conclusion These experiments, conducted in a non-human primate model, suggest that selective 5HT_2A antagonists such as EMD 281014 could offer therapeutic benefit to younger and older psychiatric patients by improving working memory function.This revised version was published online in January 2005 with corrections to the authors affiliations.     

Interactions of selective serotonin reuptake inhibitors with the serotonin 5-HT2C receptor

Interactions of the selective serotonin reuptake inhibitors (SSRIs) citalopram, fluoxetine and its main metabolite norfluoxetine, and the tricyclic anti-depressant (TCA) imipramine with the rat serotonin 5-HT_2C receptor in a clonal cell line and in the rat choroid plexus were investigated by radioligand binding and phosphoinositide (PI) hydrolysis assays. For comparison, the affinities of a variety of other antidepressants of different chemical classes for the cloned rat 5-HT_2C and 5-HT_2A receptors were also determined by radioligand binding assays. Fluoxetine displayed relatively high affinity for the 5-HT_2C receptor in the choroid plexus, with a K_i value for inhibition of [³H]mesulergine binding of 55.4 nM. The K_i values for imipramine, norfluoxetine and citalopram were 136 nM, 203 nM, and 298 nM, respectively. Similar rank order of potency was detected in PI hydrolysis assays, which showed that these drugs are antagonists at the 5-HT_2C receptor without exhibiting inverse agonist activity. [³H]Ketanserin (5-HT_2A) binding assays revealed that the SSRIs fluoxetine, norfluoxetine and citalopram show 10- to 23-fold selectivity for the 5-HT_2C receptor in vitro, whereas the TCA imipramine does not. Many other TCAs also had high to intermediate affinity for both 5-HT_2A and 5-HT_2C receptors. The present data provide evidence that fluoxetine, norfluoxetine and citalopram, along with many other antidepressant compounds, interact directly with the 5-HT_2C receptor.     

Interaction of 1,2,4-substituted piperazines, new serotonin receptor ligands, with 5-HT1A and 5-HT2A receptors

In the present paper, we describe affinities to 5-HT1A and 5-HT2A receptors of several new 1,2,4-trisubstituted piperazine derivatives. The affinities were compared with those described earlier for 1,4-disubstituted piperazines and the influence of the third (methyl) substituent on the affinity to both receptors is discussed. The difference between two- and three-substituted derivatives was rationalised in terms of molecular modelling of the respective ligand-receptor complexes. Additionally, the functional activity of some 1,2,4-trisubstituted piperazines for 5-HT1A receptor was examined in behavioural and biochemical models. The obtained results have shown that some trisubstituted compounds exhibited a higher affinity to 5-HT2A receptors than their respective disubstituted analogues (with the affinity to 5-HT1A receptors remaining the same or somewhat improving). The molecular dynamics simulations suggested that the presence of the third substituent in the piperazine ring of those compounds may induce stabilising effect on the ligand-receptor complexes. The results of the in vivo studies have shown that some of the examined trisubstituted piperazines (10-13, 16, 17) exhibited properties of postsynaptic 5-HT1A partial agonists. Moreover, compounds 13 and 16 exhibited features of 5-HT1A presynaptic agonists in in vitro test, and compound 16 also in in vivo tests.     

Antinociception in rat by sarpogrelate, a selective 5-HT(2A) receptor antagonist, is peripheral

The antinociceptive effect of sarpogrelate, a new selective 5-hydroxytriptamine (5-HT)(2A) receptor antagonist, in the formalin test was examined in rats. Sarpogrelate was administered intraperitoneally, locally (subcutaneously at the formalin test site) or intrathecally 10 min before formalin injection. Intraperitoneal (1-100 mg/kg) and local (0.01-1 mg) administration of sarpogrelate suppressed flinching behavior in both phases 1 (0-9 min) and 2 (10-60 min) in a dose-dependent manner. Intraperitoneal (100 mg/kg) and local (1 mg) injection 7 min after formalin injection reduced phase 2 flinches to the same degree as with the pre-treatment. Intrathecal administration (1-100 microg) showed no antinociceptive action, and facilitated phase 2 flinches at 10 microg. The plasma concentration of sarpogrelate after local administration of 1 mg was lower than after intraperitoneal administration of 10 mg/kg, although local administration produced more potent antinociception. The data imply that the antinociceptive effect of sarpogrelate results mainly from an action at peripheral sites.     

BIMT 17, a 5-HT2A receptor antagonist and 5-HT1A receptor full agonist in rat cerebral cortex

In the search for antidepressant agents with a rapid onset of action, we have found that compound BIMT 17 (1-[2-[4-(3-trifluoromethylphenyl)piperazin1-yl]ethyl]benzimidazol-[1H]-2-one) shows a good affinity for cerebral cortical 5-HT_1A (pK _i = 7.72) and 5-HT_2A (pK _i = 6.90) receptors, with no appreciable affinity for the other 5-HT receptor subtypes, including 5-HT_2C. BIMT 17 reduced forskolin-stimulated cAMP accumulation in the cerebral cortex (pEC₅₀ = 6.09) and in the hippocampus (pEC₅₀ = 6.50), and antagonized 5-HT-induced phosphatidylinositol turnover (pK _i = 6.96) in the cerebral cortex. The effect on cAMP accumulation was blocked by the 5-HT_1A receptor antagonist tertatolol. Buspirone, 8-OH-DPAT and S 14671 {1-[2-(2-thenoylamino)ethyl]-4[1-(7-methoxynaphtyl)]piperazine, claimed to be 5-HT_1A receptor agonists, did not reduce forskolin-stimulated cAMP formation in the cerebral cortex.On the basis of these data, it was concluded that BIMT 17 was the only compound that behaved as a full agonist with respect to the CAMP response in the cortex, while exerting concurrent agonism at 5-HT_1A receptors and antagonism at 5-HT_2A receptors. These characteristics might explain the peculiar behaviour of BIMT 17 in mimicking the inhibitory action of 5-HT on the basal firing rate of the cortical neurons (see accompanying paper).     

5-HT 2C receptor sensitivity during treatment with selective serotonin re-uptake inhibitors

We studied the effect of repeated treatment with selective serotonin re-uptake inhibitors (SSRIs) on the sensitivity of brain 5-HT(2C) receptors, by measuring the decrease in slow wave sleep (SWS) that follows administration of meta-chlorophenylpiperazine (mCPP) (7.5 mg orally). mCPP significantly lowered SWS both in patients taking SSRIs and in a group of healthy controls. There was, however, no difference in the response between the two groups. The results do not support the suggestion that repeated SSRI treatment alters the sensitivity of 5-HT(2C) receptors in the human brain. The present study, however, cannot exclude the possibility that a decrease in 5-HT(2C) receptor sensitivity was offset by higher plasma levels of mCPP in the SSRI-treated group.     

Behavioral profile of SB 269970, a selective 5-HT(7) serotonin receptor antagonist, in social encounters between male mice

The 5-HT(7) receptor is targeted by several antipsychotics, such as pimozide or clozapine, which have demonstrated antiaggressive properties in laboratory animal models. Likewise, 'in situ' hybridization and autoradiography studies have revealed moderate to high densities of 5-HT(7) receptors in limbic areas and hypothalamus, which have long been involved in the control of aggression. However, to date there is no evidence concerning the role of this receptor in the regulation of aggression. This study was designed to examine the effects of SB 269970 (1, 2, 4, 8, 16 and 32 mg/kg, i.p.), a selective 5-HT(7) receptor antagonist, on agonistic behavior elicited by isolation in mice. Individually housed mice were exposed to anosmic standard opponents 15 min after drug administration and encounters were videotaped and evaluated using an ethopharmacologically-based analysis. The results indicated that SB 269970 did not produce any significant behavioral changes, suggesting that 5-HT(7) receptors might not be involved in the modulation of aggression. Further studies with other selective ligands for these receptors are needed to confirm these findings.     

Effects of the serotonin 5-HT(2) antagonist, ritanserin, and the serotonin 5-HT(1A) antagonist, WAY 100635, on cocaine-seeking in rats

Manipulations of serotonergic systems have been shown to modify many of the behavioral effects of cocaine. It was recently demonstrated that serotonin (5-HT) depletions produced by inhibition of tryptophan hydroxylase reduced cocaine-seeking in an animal model. The present study was designed to determine whether pretreatment with specific 5-HT antagonists might also decrease cocaine-seeking. The effect of pretreatment with the 5-HT(2) antagonist, ritanserin (0.0, 1.0, or 10.0 mg/kg), or the 5-HT(1A) antagonist, WAY 100635 (0. 0, 0.1, 0.3, or 1.0 mg/kg), on cocaine (5.0, 10.0, or 20.0 mg/kg)-produced reinstatement of extinguished drug-taking behavior was measured. Although ritanserin was ineffective, WAY 100635 attenuated cocaine-produced reinstatement in a dose-dependent manner. These effects of WAY 100635 appeared to be specific since responding maintained by saccharin self-administration remained high following pretreatment with 0.3 or 1.0 mg/kg WAY 100635. These data suggest a role of 5-HT(1A), but not 5-HT(2), receptors in cocaine-seeking.     

Characterization of SB-269970-A, a selective 5-HT(7) receptor antagonist

The novel 5-HT(7) receptor antagonist, SB-269970-A, potently displaced [(3)H]-5-CT from human 5-HT(7(a)) (pK(i) 8.9+/-0.1) and 5-HT(7) receptors in guinea-pig cortex (pK(i) 8.3+/-0.2). 5-CT stimulated adenylyl cyclase activity in 5-HT(7(a))/HEK293 membranes (pEC(50) 7.5+/-0.1) and SB-269970-A (0.03 - 1 microM) inhibited the 5-CT concentration-response with no significant alteration in the maximal response. The pA(2) (8.5+/-0.2) for SB-269970-A agreed well with the pK(i) determined from [(3)H]-5-CT binding studies. 5-CT-stimulated adenylyl cyclase activity in guinea-pig hippocampal membranes (pEC(50) of 8.4+/-0.2) was inhibited by SB-269970-A (0.3 microM) with a pK(B) (8.3+/-0.1) in good agreement with its antagonist potency at the human cloned 5-HT(7(a)) receptor and its binding affinity at guinea-pig cortical membranes. 5-HT(7) receptor mRNA was highly expressed in human hypothalamus, amygdala, thalamus, hippocampus and testis. SB-269970-A was CNS penetrant (steady-state brain : blood ratio of ca. 0.83 : 1 in rats) but was rapidly cleared from the blood (CLb=ca. 140 ml min(-1) kg(-1)). Following a single dose (3 mg kg(-1)) SB-269970 was detectable in rat brain at 30 (87 nM) and 60 min (58 nM). In guinea-pigs, brain levels averaged 31 and 51 nM respectively at 30 and 60 min after dosing, although the compound was undetectable in one of the three animals tested. 5-CT (0.3 mg kg(-1) i.p.) induced hypothermia in guinea-pigs was blocked by SB-269970-A (ED(50) 2.96 mg kg(-1) i.p.) and the non-selective 5-HT(7) receptor antagonist metergoline (0.3 - 3 mg kg(-1) s.c.), suggesting a role for 5-HT(7) receptor stimulation in 5-CT induced hypothermia in guinea-pigs. SB-269970-A (30 mg kg(-1)) administered at the start of the sleep period, significantly reduced time spent in Paradoxical Sleep (PS) during the first 3 h of EEG recording in conscious rats.     

BIMT 17, a 5-HT1A receptor agonist/5-HT2A receptor antagonist,directly activates postsynaptic 5-HT inhibitory responses in the rat cerebral cortex

BIMT 17 (1-[2-[4-(3-trifluoromethyl phenyl) piperazin-1-yl] ethyl] benzimidazol- [1H]-2-one), a 5-HT_1A receptor agonist/5-HT_2A receptor antagonist (see Borsini et al., accompanying paper), in a dose range of 1–10 mg/kg i.v., dose-dependently inhibited the electrical activity of rat medial prefronto-cortical neurons, whereas buspirone, in a dose range of 0.1–1000 g/kg, increased it. 8-hydroxy-2-(di-n-propylamino) tetralin (8-OH-DPAT) and 1-[2-(2-thenoylamino)ethyl]-4[1-(7-methoxynaphthyl)] piperazine (S 14671) presented biphasic patterns of response; they increased electrical activity at doses in the range of 0.1–10 g/kg and 0.1–3 g/kg i.v. respectively, and reduced it at higher doses, 30–300 g/kg and 10–30 g/kg i.v., respectively.The inhibitory effect of BIMT 17 on the firing rate of neurons in the frontal cortex was antagonized by the 5-HT_1A antagonists tertatolol and WAY 100135, and was still present after destruction of serotonin (5-HT) containing neuronal endings by the neurotoxin 5,7-dihydroxytryptamine (5,7-DHT; 150 g/rat, given intraventricularly), which reduced the cortical 5-HT content by 85%. This destruction of 5-HT neurons, while suppressing the ability of 8-OH-DPAT to inhibit the firing rate at high doses, did not change the excitatory action of this compound at low doses. The addition of ritanserin, a 5-HT2A receptor antagonist, potentiated both the excitatory and inhibitory effects of 8-OHDPAT on neuronal electrical activity. Direct microiontophoretic application (100 nA/20 s) of 5-HT and BIMT 17, but not that of 8-OH-DPAT, onto medial prefronto-cortical neurons, decreased the firing rate of these neurons.These findings suggest that BIMT 17 directly inhibits the electrical activity of medial prefronto-cortical neurons through its dual mode of receptor interaction.     

5-HT3 receptor antagonism by anpirtoline, a mixed 5-HT1 receptor agonist/5-HT3 receptor antagonist.

1. The aim of this study was to provide evidence that anpirtoline, which is an agonist at 5-HT1B and 5-HT1D receptors and also displays submicromolar affinity for 5-HT1A recognition sites, in addition, acts as an antagonist at 5-HT3 receptors. 2. In radioligand binding studies on rat brain cortical membranes, anpirtoline inhibited specific binding of [3H]-(S)-zacopride to 5-HT3 receptor recognition sites (pKi: 7.53). 3. In N1E-115 neuroblastoma cells in which [14C]-guanidinium was used as a tool to measure cation influx through the 5-HT3 receptor channel, the 5-HT-induced influx was concentration-dependently inhibited by anpirtoline. In this respect, anpirtoline mimicked other 5-HT3 receptor antagonists; the rank order of potency was ondansetron > anpirtoline > metoclopramide. 4. The concentration-response curve for 5-HT as a stimulator of [14C]-guanidinium influx was shifted to the right by anpirtoline (apparent pA2: 7.78). 5. In urethane-anaesthetized rats, anpirtoline inhibited (at lower potency than zacopride and tropisetron) the 5-HT- or phenylbiguanide-induced bradycardia (Bezold-Jarisch reflex), but did not induce this reflex by itself. 6. Intravenous infusion of cisplatin in the domestic pig caused a consistent emetic response which was antagonized by anpirtoline. 7. It is concluded that anpirtoline, which was previously characterized as a 5-HT1 receptor agonist also proved to be a 5-HT3 receptor antagonist in several experimental models and, hence, exhibits a unique pattern of properties at different 5-HT receptors.     

Synthesis of new arylpiperazinylalkylthiobenzimidazole, benzothiazole, or benzoxazole derivatives as potent and selective 5-HT1A serotonin receptor ligands

A series of new compounds containing a benzimidazole, benzothiazole, or benzoxazole nucleus linked to an arylpiperazine by different thioalkyl chains was prepared. They were tested in radioligand binding experiments to evaluate their affinity for 5-HT 1A and 5-HT 2A serotonergic, alpha 1 adrenergic, D1, and D2 dopaminergic receptors. Many of tested compounds showed an interesting binding profile; in particular, 36 displayed very high 5-HT 1A receptor affinity and selectivity over all the other investigated receptors. Selected compounds, evaluated in functional assays, showed antagonistic or partial agonistic activity at 5-HT 1A receptor. An extensive conformational research using both NMR and modeling techniques indicated that extended conformations predominated in vacuum, in solution and during interactions with 5-HT 1A receptor. Finally, the elaborated binding mode of selected compounds at 5-HT 1A receptor was used to explain the influence of spacer length on ligands affinity.