Selective 5-HT1A Receptor Antagonist Research Articles

Antidepressant-like effect of aripiprazole via 5-HT1A, D1, and D2 receptors in the prefrontal cortex of olfactory bulbectomized mice

Olfactory bulbectomized (OBX) mice exhibit depressive-like behaviors and memory deficits. We have reported that aripiprazole (ARI) ameliorates the behavioral hyper-responsivity to dopamine agonists and memory deficits in OBX mice; however, it is unclear whether ARI affects OBX-induced depressive-like behavior. To address this question, we evaluated the effect of ARI on depressive-like behavior in OBX mice using the forced swim test (FST). In addition, we investigated the effect of ARI on c-Fos expression in the prefrontal cortex (PFC), striatum, and hippocampus of OBX mice using western blotting. OBX mice exhibited a longer immobility duration in the FST 14 days after surgery. Depressive-like behavior in OBX mice was reversed 30 min after administration of ARI (0.01 or 0.03 mg/kg). In addition, c-Fos expression was increased in the PFC, but not the striatum or hippocampus, 30 min after acute administration of ARI. These effects were inhibited by administration of the selective 5-HT1A, D1, and D2 receptor antagonists, WAY100635, SCH23390, and L-741,626, respectively. These findings suggest that ARI produces an antidepressant effect in OBX mice that may be mediated by 5-HT1A, D1, and D2 receptors in the PFC.

A behavioral mechanistic investigation of the role of 5-HT1A receptors in the mediation of rat maternal behavior

Previous work suggests that 5-HT1A receptors play a special role in rodent maternal aggression, but not in other aspects of maternal care (e.g. pup retrieval and nest building). The present study re-assessed the basic effects of 5-HT1A activation or blockade on various maternal responses in postpartum female rats. We also examined the possible behavioral mechanisms underlying the maternal effects of 5-HT1A. Sprague–Dawley mother rats were injected with a 5-HT1A agonist 8-OH-DPAT (0.1, 0.5 or 1.0 mg/kg, sc), a 5-HT1A antagonist WAY-101405 (0.1, 0.5 or 1.0 mg/kg, sc) or 0.9% saline solution on postpartum days 3, 5, and 7. Maternal behavior was tested 30 min before, 30 min, 120 min, and 240 min after the injection. Acute and repeated 8-OH-DPAT treatment significantly disrupted pup retrieval, pup licking, nursing, and nest building in a dose-dependent fashion, whereas WAY-101405 had no effect at the tested doses. The 5-HT1A receptor specificity of 8-OH-DPAT's action was confirmed as its maternal disruption effect was reversed by pretreatment of WAY-100635 (a highly selective 5-HT1A receptor antagonist). Subsequent pup preference test found that 8-OH-DPAT did not decrease the pup preference over a novel object, thus no inhibition on maternal motivation or maternal affect. The pup separation test and pup retrieval on an elevated plus maze test also failed to find any motivational and motor impairment effect with 8-OH-DPAT. However, 8-OH-DPAT at the maternal disruptive dose did disrupt the prepulse inhibition (a measure of attentional function) of acoustic startle response and enhanced the basal startle response. These findings suggest that stimulation of 5-HT1A receptors by 8-OH-DPAT impairs maternal care by partially interfering with the attentional processing or basal anxiety. More work is needed to further delineate the psychological and neuronal mechanisms underlying the maternal disruptive effect of 5-HT1A receptor activation.

Functional mechanism of ASP5736, a selective serotonin 5-HT5A receptor antagonist with potential utility for the treatment of cognitive dysfunction in schizophrenia

The 5-HT5A receptor is arguably the least understood 5-HT receptor. Despite widespread expression in human and rodent brains it lacks specific ligands. Our previous results suggest that 5-HT5A receptor antagonists may be effective against cognitive impairment in schizophrenia. In this study, using behavioral, immunohistochemical, electrophysiological and microdialysis techniques, we examined the mechanism by which ASP5736, a novel and selective 5-HT5A receptor antagonist, exerts a positive effect in animal models of cognitive impairment. We first confirmed the effect of ASP5736 on cognitive deficits in rats treated subchronically with phencyclidine hydrochloride (PCP) using an attentional set shifting task. Subsequently, we identified 5-HT5A receptors in dopaminergic (DAergic) neurons and parvalbumin (PV)-positive interneurons in the ventral tegmental area (VTA) and in PV-positive interneurons in the medial prefrontal cortex (mPFC). Burst firing of the DAergic cells in the parabrachial pigmental nucleus (PBP) in the VTA, which predominantly project to the mPFC, was significantly enhanced by treatment with ASP5736. In contrast, ASP5736 exerted no significant effect on either the firing rate or burst firing in the DA cells in the paranigral nucleus (PN), that project to the nucleus accumbens (N. Acc.). ASP5736 increased the release of DA and gamma-aminobutyric acid (GABA) in the mPFC of subchronically PCP-treated rats. These results support our hypothesis that ASP5736 might block the inhibitory 5-HT5A receptors on DAergic neurons in the VTA that project to the mPFC, and interneurons in the mPFC, and thereby improve cognitive impairment by preferentially enhancing DAergic and GABAergic neurons in the mPFC.

Anxiolytic and antidepressant activities of Pelargonium roseum essential oil on Swiss albino mice: Possible involvement of serotonergic transmission.

The anxiolytic and antidepressant activities of the Reunion Geranium (Pelargonium roseum Willd) essential oil (EO) were evaluated in male Swiss albino mice by intraperitoneal administration of 10, 20, and 50mg/kg bw using elevated plus maze (EPM), open-field test (OFT), and forced swimming test (FST). Moreover, we evaluated whether the 5-HT1A and GABAA -benzodiazepine receptor systems are involved in the anxiolytic effects through the coadministration of WAY-100635 (a selective 5-HT1A receptor antagonist) and flumazenil (an antagonist of benzodiazepine). GC-MS revealed the monoterpene alcohols citronellol (35.9%) and geraniol (18.5%) as the main components of the P.roseum EO. EO was effective in increasing the total number of entries and time spent in the open arms of EPM whereas number of rearing in OFT was significantly decreased in comparison with the control. In the FST, immobility time decreased in EO treated mice. Pretreatment with WAY-100635, but not Flumazenil, was able to reverse the effects of the EO in the EPM and FST, indicating that the EO activity occurs via the serotonergic but not GABAergic transmission. Overall, results of this work showed significant anxiolytic and antidepressant activity of P.roseum EO and confirmed the traditional uses of Pelargonium species as calming agents.

Evaluation of the safety, tolerability, and efficacy of pimavanserin versus placebo in patients with Alzheimer's disease psychosis: a phase 2, randomised, placebo-controlled, double-blind study

Pimavanserin is a selective 5-HT2A receptor inverse agonist and antagonist approved in the USA for the treatment of hallucinations and delusions associated with Parkinson's disease psychosis. No safe or effective pharmacological treatment is approved for psychosis in patients with Alzheimer's disease. Therefore, we aimed to evaluate the safety, tolerability, and efficacy of pimavanserin versus placebo in patients with Alzheimer's disease psychosis. We did a phase 2, randomised, double-blind, placebo-controlled, single-centre (with multiple affiliated nursing home sites across the UK) study. We included participants of either sex who were aged 50 years or older with possible or probable Alzheimer's disease and psychotic symptoms including visual or auditory hallucinations, delusions, or both. Participants were randomly assigned (1:1) to 12 weeks of oral treatment with either pimavanserin (two 17 mg tablets daily) or placebo, with use of permuted block sizes of four and stratified by baseline Mini-Mental State Examination (MMSE) total score (<6 or ≥6) and Neuropsychiatric Inventory-Nursing Home version (NPI-NH) psychosis score (<12 or ≥12). Participants, caregivers, the study sponsor, and study personnel at the clinic site were masked to treatment assignment. The primary endpoint was mean change from baseline to week 6 in the NPI-NH psychosis score for pimavanserin versus placebo in the modified intention-to-treat population. Sustained benefit and safety of pimavanserin were assessed through week 12. This study is registered at ClinicalTrials.gov, number NCT02035553. Between Jan 16, 2014, and Oct 27, 2016, 345 participants across 133 nursing homes were screened, of whom 181 were randomly assigned treatment (n=90 pimavanserin and n=91 placebo). 178 participants were included in the modified intention-to-treat population. Mean total baseline NPI-NH psychosis scores were 9·5 (SD 4·8) for the pimavanserin group and 10·0 (5·6) for the placebo group. Mean change in the NPI-NH psychosis score at week 6 was -3·76 points (SE 0·65) for pimavanserin and -1·93 points (0·63) for placebo (mean difference -1·84 [95% CI -3·64 to -0·04], Cohen's d=-0·32; p=0·045). By week 12, no significant advantage for pimavanserin versus placebo was observed for the overall study population (treatment difference -0·51 [95% CI -2·23 to 1·21]; p=0·561). Common adverse events were falls (21 [23%] of 90 participants in the pimavanserin group vs 21 [23%] of 91 in the placebo group), urinary tract infections (20 [22%] vs 25 [28%]), and agitation (19 [21%] vs 13 [14%]). Eight (9%) participants on pimavanserin and 11 (12%) on placebo discontinued treatment because of adverse events. No detrimental effect was observed on cognition or motor function in either group. Pimavanserin showed efficacy in patients with Alzheimer's disease psychosis at the primary endpoint (week 6) with an acceptable tolerability profile and without negative effect on cognition. Further follow-up to week 12 did not show significant advantage for pimavanserin versus placebo. ACADIA Pharmaceuticals.

Contribution of spinal 5-HT5A receptors to the antinociceptive effects of systemically administered cannabinoid agonist WIN 55,212-2 and morphine.

The antinociceptive effects of cannabinoids and opioids have been known for centuries. Serotonin and its receptors are also known to play important roles in nociception. However, the contribution of spinal 5-HT5A receptors in antinociceptive effects of cannabinoids and opioids has not been studied. We conducted this study to clarify spinal mechanisms of the actions of the antinociceptive effects of cannabinoids and opioids. Hot plate and tail flick tests were used to assess the antinociceptive activity in Balb/c mice. WIN 55,212-2, a nonselective CB1 and CB2 agonist, and morphine exerted significant antinociceptive effects at 1, 3, and 10 mg/kg doses administered intraperitoneally in both hot plate and tail flick tests. The selective 5-HT5A receptor antagonist SB-699551 (10 nmol/mouse) was administered intrathecally 10 min before the agonists. SB-699551 significantly reduced the antinociceptive effect of both WIN 55,212-2 and morphine. In the rotarod test, WIN 55,212-2 disrupted the motor coordination at a dose of 10 mg/kg, while morphine did not affect this function at any dose. Our findings show that spinal 5-HT5A receptors are involved in the antinociceptive effects of WIN 55,212-2 and morphine.

Further investigation of the effects of 5-hydroxytryptamine, 8-OH-DPAT and DOI to mediate contraction and relaxation responses in the intestine and emesis in Suncus murinus

5-HT receptors are implicated in many gastrointestinal disorders. However, the precise role of 5-HT in mediating GI responses in Suncus murnius is still unclear. Therefore in this study, the effects of 5-HT and its agonists were investigated in Suncus. The involvement of 5-HT2C receptors in mediating emesis was also investigated. The ability of 5-HT and its agonists/antagonists at 5-HT1A and 5-HT2 to modify GI motility was investigated in vitro and in vivo.WAY100635 (a 5-HT1A antagonist) inhibited the contraction response to 5-HT in the proximal segments without affecting the maximum response; whilst enhancing the contraction to 5-HT (>30.0nM) in the distal intestine. The selective 5-HT2A and 5-HT2B receptor antagonists MDL-100907 and RS-127445 attenuated 5-HT-induced contractions (<10.0µM) in the distal segments. RS-127445 also attenuated 5-HT-induced contractions in the central segments. The selective 5-HT2C receptor antagonist SB-242084, attenuated the responses to 5-HT (> 3.0nM) in the proximal and central but not the distal regions. 8-OH-DPAT-induced relaxation was resistant to the antagonism by 5-HT1A/7 antagonists. DOI in the presence of 5-HT1A/2A/2B/2C antagonists induced greater contraction responses (>1.0µM) in most tissues, whilst RS-127445, or SB-242084, reduced the responses to DOI (< 1.0µM) in some tissues. SB-242084 also suppressed emesis-induced by motion and intragastric CuSO4.In conclusion, within different regions of intestine, 5-HT2 receptors are differently involved in contraction and emetic responses and that 8-OH-DPAT induces relaxation via non-5-HT1A/7 receptors. Suncus could provide a model to investigate these diverse actions of 5-HT.

Activity of Serotonin 5-HT1A Receptor Biased Agonists in Rat: Anxiolytic and Antidepressant-like properties.

Although serotonin 5-HT1A receptors constitute attractive therapeutic targets, there is a lack of potential clinical candidates that have a high degree of selectivity and full agonist efficacy. Recently, novel 5-HT1A receptor "biased agonists" F15599 (also known as NLX-101) and F13714 have been reported that exhibit distinctive properties for in vitro signaling, neurochemical, electrophysiological effects, and in brain imaging. The present study characterized their effects in rat models of anxiety (elevated plus-maze, EPM, and Vogel tests), in depressive-like behavior (forced swim test), and on the induction of the three serotonergic behaviors (forepaw treading, flat body posture, and lower lip retraction). The prototypical 5-HT1A receptor ligands (±)8-OH-DPAT and buspirone were tested as comparators. In the elevated plus-maze, F15599, F13714, and (±)8-OH-DPAT dose-dependently increased the amount and percentage of time spent in the open arms with minimal effective doses (MED) of 5 mg/kg p.o., 2.5 mg/kg p.o. and 1.25 mg/kg s.c., respectively. The effects of the three agonists were abolished by pretreatment with the selective 5-HT1A receptor antagonist, WAY100635 (0.63 mg/kg s.c.). Buspirone did not show significant activity in the EPM. In contrast, in the Vogel test only buspirone was active, significantly increasing the number of licks and shocks accepted (active dose: 1.25 mg/kg s.c.). However, WAY100635 failed to reverse the effects of buspirone in this test, suggesting that they were not 5-HT1A receptor-mediated. In the forced swim test, F15599, F13714, and (±)8-OH-DPAT were potently active, abolishing immobility (MED: 0.63 mg/kg p.o., 0.63 mg/kg p.o. and 0.16 mg/kg s.c., respectively). Buspirone was not active. In measures of serotonergic behavior, F13714 and (±)8-OH-DPAT robustly elicited all three signs of serotonergic behaviors, whereas F15599 and buspirone elicited only lower-lip retraction. Taken together, these observations highlight the distinct profiles of activity of 5-HT1A agonists and suggest that the novel biased agonist F15599 combines pronounced activity in a test of anxiety (elevated plus-maze) with potent antidepressant-like effects and low propensity to induce serotonergic behaviors. These data suggest that selective biased agonists could constitute promising pharmacotherapeutics for mood disorders.

NLX-112, a highly selective 5-HT1A receptor agonist: Effects on body temperature and plasma corticosterone levels in rats

NLX-112 (a.k.a. F13640 or befiradol), exhibits nanomolar affinity, exceptional selectivity and high agonist efficacy at 5-hydroxytryptamine 5-HT1A receptors. It possesses marked activity in a variety of animal models of depression, pain and L-DOPA-induced dyskinesia. However, its influence on translational biomarkers of central 5-HT1A receptor activation has not been previously described. Here, we report on the activity, in rats, of NLX-112 to increase plasma corticosterone levels and produce hypothermia, two responses which are also elicited by 5-HT1A receptor agonists in humans.NLX-112 elicited dose-dependent hypothermia (minimal effective dose, MED: 0.31mg/kg p.o.) and also increased plasma corticosterone both by oral and intraperitoneal routes (MED: 0.63mg/kg in both cases). The increase in corticosterone induced by NLX-112 (0.63mg/kg p.o.) was abolished by co-administration of the selective 5-HT1A receptor antagonist, WAY100635. Additionally, NLX-112 also dose-dependently induced flat body posture, forepaw treading and lower lip retraction (MEDs 0.31–0.63mg/kg p.o.).The doses of NLX-112 which induce hypothermia or corticosterone release were similar to those inducing serotonergic behaviors but greater than those reported previously in models of therapeutic-like activity (range 0.04 to 0.16mg/kg). Overall, the present study provides information for clinical dose estimations of NLX-112 and suggests that therapeutic effects may occur at doses below those at which biomarker responses are observed.

Selective Serotonin 5-HT2A Receptor Antagonists and Inverse Agonists Specifically Promote Slow Wave Sleep (Stage N3) in Man

Several drug classes are widely prescribed when difficulties with sleep induction or sleep maintenance occur, as is the case in patients with an insomnia disorder. These include the benzodiazepine and non-benzodiazepine receptor allosteric modulators, the melanin receptor agonist ramelteon, low-dose doxepin, and the orexin receptor antagonist suvorexant. Benzodiazepines are often less than satisfactory, since they are known to produce reductions in both N3 sleep and rapid-eye movement (REM) sleep. Similarly, low-dose doxepin has been associated with a reduction in REM sleep. Initially, it was shown that the non-selective serotonin 5-HT2A/2C receptor antagonists’ ritanserin, ketanserin, seganserin, and ICI-169,369 increase N3 sleep in subjects with normal sleep. Ritanserin produced also an increase of N3 sleep in poor sleepers, patients with a chronic insomnia disorder, and psychiatric patients with a generalized anxiety disorder or a mood disorder. More recent evidence indicates that the selective 5-HT2A receptor antagonist volinanserin and the 5-HT2A receptor inverse agonists’ nelotanserin and pimavanserin significantly increase N3 sleep in subjects with normal sleep. Nelotanserin was also shown to augment N3 sleep in patients with a chronic insomnia disorder. N2 sleep tended to decrease in most of these studies, while REM sleep showed no significant changes. The present review which summarizes these findings is the basis for a proposal for a new therapeutic strategy. It is proposed that the co-administration of a selective 5-HT2A receptor antagonist or inverse agonist along with a hypnotic drug could be a valid clinical strategy for normalizing sleep induction and maintenance and for promoting N3 sleep in patients with an insomnia disorder.

Ameliorative effect of chlorpromazine hydrochloride on visceral hypersensitivity in rats: possible involvement of 5-HT2A receptor.

Visceral hypersensitivity is responsible for pathogenesis of irritable bowel syndrome (IBS). Therefore, its prevention can help avoid abdominal pain and discomfort in IBS. To find candidate drugs for visceral hypersensitivity, we screened existing medicines for their ability to prevent visceral sensitivity induced by colorectal distension (CRD) in rats and identified chlorpromazine, a typical antipsychotic drug, as a candidate compound. In this study, we investigated the effect of chlorpromazine on visceral hypersensitivity. Visceral sensitivity (visceromotor response) was monitored by measuring the electrical activity of the abdominal external oblique muscle contraction in response to CRD using a barostat apparatus. Visceral hypersensitivity was induced by a colonic instillation of sodium butyrate or acetic acid in neonates. Oral administration of chlorpromazine suppressed butyrate-induced visceral hypersensitivity to CRD. Interestingly, atypical antipsychotic drugs, quetiapine and risperidone, ameliorated butyrate-induced visceral hypersensitivity, whereas the typical antipsychotic drugs, haloperidol and sulpiride, did not. Pharmacological analysis using specific inhibitors showed that a selective 5-HT2A receptor antagonist, ketanserin, suppressed butyrate-induced visceral hypersensitivity, whereas a selective dopamine D2 receptor antagonist, L-741626, did not. Furthermore, the 5-HT2A receptor agonist AL-34662 stimulated visceral sensitivity to CRD in healthy control rats but not in butyrate-treated rats. These findings suggest that increased 5-HT levels in the colon contribute to the induction of visceral hypersensitivity. Our results indicate that chlorpromazine ameliorates visceral hypersensitivity and that the 5-HT2A receptor is a potential therapeutic target for treating abdominal pain and discomfort in IBS.

Antinociceptive, antiallodynic and antihyperalgesic effects of the 5-HT1A receptor selective agonist, NLX-112 in mouse models of pain

Background and purpose:NLX-112 (a.k.a. befiradol, F13640) is a drug candidate intended for the treatment of l-DOPA-induced dyskinesia. It is a highly selective serotonin 5-HT1A receptor full agonist which has been previously tested in a variety of models of CNS effects including analgesic activity in rat. Its activity in mouse models of pain has not been previously investigated. Experimental approachThe activity of NLX-112 was tested in mouse models of acute pain (hot plate), tonic pain (intraplantar formalin test), in the oxaliplatin-induced neuropathic pain model of chemotherapy-induced peripheral neuropathy and in the streptozotocin (STZ)-induced model of painful diabetic neuropathy. Key resultsThe main findings indicate that (i) NLX-112 was markedly active in the formalin test with potent reduction of paw licking in both phases of the test (minimal effective dose (MED) 0.5 mg/kg i.p. and p.o. in acute phase, and 0.1 mg/kg i.p. and 1 mg/kg p.o. in late phase). The effects of NLX-112 in this test were completely abolished by the selective 5-HT1A receptor antagonist, WAY100635; (ii) NLX-112 was active in the hot plate test and in the oxaliplatin-induced neuropathic pain model of chemotherapy-induced peripheral neuropathy, but at markedly higher doses (MED 2.5 mg/kg i.p.); (iii) NLX-112 was least active in the STZ-induced model of painful diabetic neuropathy (MED 5 mg/kg i.p.); (iv) NLX-112 did not affect locomotor activity. Conclusions and implicationsNLX-112 may have significant potential for treatment of tonic pain but may be less promising as a candidate for treatment of chemotherapy-induced or diabetic neuropathic pain.

Synergic stimulation of serotonin 5-HT1A receptor and α2-adrenoceptors for neuropathic pain relief: Preclinical effects of 2-substituted imidazoline derivatives

Neuropathic pain affects millions of people causing disability and impairing quality of life. Commonly used analgesics are generally characterized by limited therapeutic outcomes. The serotonin 5‐HT1A receptor and the α2 adrenergic receptors are involved in central nociceptive mechanisms with a pivotal role in the inhibitory descending pain pathway. Since their stimulation may modulate the nervous signaling altered by neuropathies, the purpose of the present research is the study of the combined activation of 5‐HT1A and α2 receptors by rationally designed imidazoline ligands ((S)-(-)-1 and 2–5) in a rat model of neuropathic pain (chronic constriction injury - CCI). On day 14 after nerve damage, the acute administration per os (p.o.) of low doses of (S)-(-)-1 (0.1–1mg/kg) was able to significantly increase the pain threshold to mechanical noxious stimuli for more than 1h. (S)-(-)-1 efficacy was confirmed by the decrease of spontaneous pain evaluated as hind limb weight bearing alterations. The clinically-used compound gabapentin (100mg/kg p.o.) induced a pain relieving effect similar to (S)-(-)-1 administered at 100 fold lower dose. In the same model, the selected analogues, compounds 2–5 (1mg/kg p.o.) were effective 30min after administration. In particular, 5 fully reverted the CCI-induced hypersensitivity. The pain relieving activity of 5 was significantly prevented by the selective 5-HT1A receptor antagonist WAY 100635 (1mg/kg intraperitoneally, i.p.) and, at a lesser extent, by the α2 antagonist yohimbine (3mg/kg i.p.). A novel pharmacodynamic approach to the treatment of neuropathic pain is presented.

22-azidosalvinorin A exhibits antidepressant-like effect in mice

The increasing cases of depression has made the searches for new drugs and understanding of the underligning neurobiology of this psychiatric disorder a necessity. Here, we modified the structure of salvinorin A (a known halucinogen) and investigated antidepressant-like activity of its four derivatives; 22-methylsulfanylsalvinorin A(SA1), 2-O-cinnamoylsalvinorin B (CSB), 22-azidosalvinorin A (SA2), and 2-O-(4’-azidophenylsulfonyl)salvinorin B (SA3). Prior to behavioural tests (Irwin test, open field test – OFT, forced swimming test – FST and tail suspension test – TST), SA1 was prepared by reacting salvinorin B and methylthioacetic acid with 89% yield; CSB was obtained from the reaction of salvinorin B and cinnamic acid with 92% yield; SA2 was obtained from the reaction of salvinorin B and azidoacetic acid with 81% yield; and SA3 was prepared by reacting salvinorin B with 4-azidophenylsulfonyl chloride with 80% yield. Oral treatment of mice with these derivatives (1–1000mg/kg) did not elicit toxic sign or death. Unlike SA, SA1, CSB and SA3, treatment with SA2 (5, 10 and 20mg/kg) decreased the immobility (TST and FST) and swimming time (FST) without altering locomotor activity in OFT. A decrease in the immobility time in TST and FST confirmed antidepressant-like property of SA2. Although p-chlorophenylalanine (serotonin depletor) or WAY100635 (selective 5-HT1A receptor antagonist) did not attenuate effect of SA2, alpha-methyl-para-tyrosine (catecholamine depletor) and prazosin (selective α1-receptor antagonist) attenuated this effect. SA2 mildly inhibited monoamine oxidase and showed affinity for α1A, α1B, α1D and κ-opioid receptor subtypes. In summary, SA2 induced monoamine-mediated antidepressant-like effect.

Levo-Tetrahydroberberrubine Produces Anxiolytic-Like Effects in Mice through the 5-HT1A Receptor.

Tetrahydroprotoberberines (THPBs) are isoquinoline alkaloids isolated from the Chinese herb Corydalis yanhusuo. In the present study, we performed competitive binding assays to examine the binding of l-THBr to neurotransmitter receptors known to be involved in sedation, hypnosis and anxiety. Our results show that l-THBr does not interact with GABAergic receptors but has binding affinities for dopamine and serotonin receptors. In addition, cAMP and [35S]GTPγS assays were used to determine the agonist or antagonist properties of l-THBr at dopamine (D1, D2) or serotonin (5-HT) receptors. Our results show that l-THBr displays D1 and D2 antagonist and 5-HT1A agonist properties. Moreover, l-THBr-treated rodents exhibit anxiolytic-like effects in the light/dark box and elevated plus-maze tests, and the anxiolytic effect of l-THBr can be reduced by WAY-100635, a selective 5-HT1A receptor antagonist. Our results suggest that l-THBr may produce potent anxiolytic-like effects mainly through serotonin receptors.

Effect of sarpogrelate, a selective 5-HT2A receptor antagonist, on characteristics of coronary artery disease in patients with type 2 diabetes

Background and aimsSarpogrelate, a 5-hydroxytryptamine type 2A antagonist, is a potential antiplatelet agent. We performed a randomized study to evaluate the effect of sarpogrelate on vascular health in Korean patients with diabetes. MethodsForty diabetic patients aged 58.6 ± 6.8 years with 10–75% coronary artery stenosis, as assessed by coronary computed tomography angiography, were randomly assigned to sarpogrelate 300 mg/day plus aspirin 100 mg/day (SPG + ASA group) or aspirin 100 mg/day alone (ASA group) for 6 months. The primary endpoint of this study was the change in coronary artery disease including the calcium score (CACS), maximal stenosis, and plaque volume (calcified vs. noncalcified). The secondary endpoints were changes in biochemical parameters related to glucose and lipid metabolism, and in subclinical atherosclerosis assessed by ankle–brachial index and pulse wave velocity. ResultsAfter 6-month treatment, there was no significant difference in the changes in CACS, coronary stenosis, ankle–brachial index, and pulse wave velocity, between groups. The total plaque volume decreased from 82.4 ± 14.5 mm3 to 74.6 ± 14.4 mm3 in the SPG + ASA group, but increased from 64.9 ± 16.0 mm3 to 68.6 ± 16.3 mm3 in the ASA group (p < 0.05), mainly driven by changes in the noncalcified component (SPG + ASA group 15.6 ± 4.6 mm3 to 11.2 ± 3.7 mm3vs. ASA group 21.2 ± 6.2 mm3 to 22.8 ± 6.6 mm3, p < 0.01). Serum C-reactive protein levels and homeostasis model assessment of insulin resistance tended to decrease in the SPG + ASA group, but they were not altered in the ASA group. ConclusionsThe present study demonstrated that sarpogrelate treatment may decrease coronary artery plaque volume, particularly the noncalcified portion, in patients with diabetes.

Anti-allodynic effect of mangiferin in neuropathic rats: Involvement of nitric oxide-cyclic GMP-ATP sensitive K+ channels pathway and serotoninergic system

The neurobiology of neuropathic pain is caused by injury in the central or peripheral nervous system. Recent evidence points out that mangiferin shows anti-nociceptive effect in inflammatory pain. However, its role in inflammatory and neuropathic pain and the possible mechanisms of action are not yet established. The purpose of this study was to determine the possible anti-allodynic effect of mangiferin in rats with spinal nerve ligation (SNL). Furthermore, we sought to investigate the possible mechanisms of action that contribute to these effects. Mechanical allodynia to stimulation with the von Frey filaments was measured by the up and down method. Intrathecal administration of mangiferin prevented, in a dose-dependent fashion, SNL-induced mechanical allodynia. Mangiferin-induced anti-allodynia was prevented by the intrathecal administration of L-NAME (100μg/rat, non-selective nitric oxide synthase inhibitor), ODQ (10μg/rat, inhibitor of guanylate-cyclase) and glibenclamide (50μg/rat, channel blocker of ATP-sensitive K+ channels). Moreover, methiothepin (30μg/rat, non-selective 5-HT receptor antagonist), WAY-100635 (6μg/rat, selective 5-HT1A receptor antagonist), SB-224289 (5μg/rat, selective 5-HT1B receptor antagonist), BRL-15572 (4μg/rat, selective 5-HT1D receptor antagonist) and SB-659551 (6μg/rat, selective 5-HT5A receptor antagonist), but not naloxone (50μg/rat, non-selective opioid receptor antagonist), were able to prevent mangiferin-induced anti-allodynic effect. These data suggest that the anti-allodynic effect induced by mangiferin is mediated at least in part by the serotoninergic system, involving the activation of 5-HT1A/1B/1D/5A receptors, as well as the nitric oxide-cyclic GMP-ATP-sensitive K+ channels pathway, but not by the opioidergic system, in the SNL model of neuropathic pain in rats.

Agonist and antagonist bind differently to 5-HT1A receptors during Alzheimer’s disease: A post-mortem study with PET radiopharmaceuticals

PET imaging studies using 5-HT1A receptor radiotracers show a decreased density of this receptor in hippocampi of patients with Alzheimer’s disease (AD) at advanced stages. However, current 5-HT1A receptor radiopharmaceuticals used in neuroimaging are antagonists, thought to bind to 5-HT1A receptors in different functional states (i.e., both the one which displays high affinity for agonists and is thought to mediate receptor activation, as well as the state which has low affinity for agonists). Comparing the PET imaging obtained using an agonist radiotracer, which binds selectively to functional receptors, with the PET imaging obtained using an antagonist radiotracer would therefore provide original information on 5-HT1A receptor impairment during AD. Quantitative autoradiography using [18F]F13640 and [18F]MPPF, a 5-HT1A agonist and antagonist, respectively, was measured in hippocampi of patients with AD (n = 25, at different Braak stages) and control subjects (n = 9). The neuronal density was measured in the same tissues by NeuN immunohistochemistry. The specific binding of both radiotracers was determined by addition of WAY-100635, a selective 5-HT1A receptor antagonist. The autoradiography distribution of both 5-HT1A PET radiotracers varied across hippocampus regions. The highest binding density was in the pyramidal layer of CA1. Incubation with Gpp(NH)p, a non-hydrolysable analogue of GTP, reduced significantly [18F]F13640 binding in hippocampal regions, confirming its preferential interaction with G-coupled receptors, and slightly increased [18F]MPPF binding. In the CA1 subfield, [18F]F13640 binding was significantly decreased at Braak stages I/II (−19%), Braak stages III/IV (−23%), and Braak stages V/VI (−36%) versus control. In contrast, [18F]MPPF binding was statistically reduced only at the most advanced Braak stages V/VI compared to control (−33%).Since [18F]F13640 and [18F]MPPF can be used in vivo in humans, this neuropharmacological paradigm supports testing the concept of functional imaging using agonist radiopharmaceuticals in future clinical studies.

Biphasic Effects of α-Asarone on Immobility in the Tail Suspension Test: Evidence for the Involvement of the Noradrenergic and Serotonergic Systems in Its Antidepressant-Like Activity.

Alpha (α)-asarone is one of the main psychoactive compounds, present in Acorus species. Evidence suggests that the α-asarone possess an antidepressant-like activity in mice. However, the exact dose-dependent effect of α-asarone and mechanism(s) involved in the antidepressant-like activity are not clear. The present study aimed to investigate the dose-dependent effect of α-asarone and the underlining mechanism(s) involved in the antidepressant-like activity of α-asarone in the mouse model of tail suspension test (TST). In this study, the acute effect of α-asarone per se at different doses (10–100 mg/kg, i.p.) on immobility in the TST was studied. Additionally, the possible mechanism(s) involved in the antidepressant-like effect of α-asarone was studied using its interaction with noradrenergic and serotonergic neuromodulators in the TST. The present results reveal that the acute treatment of α-asarone elicited biphasic responses on immobility such that the duration of the immobility time is significantly reduced at lower doses (15 and 20 mg/kg, i.p.) but increased at higher doses (50 and 100 mg/kg, i.p.) in the TST. Besides, α-asarone at higher doses (50 and 100 mg/kg, i.p.) significantly decreased the spontaneous locomotor activity. Moreover, pretreatment of mice with noradrenergic neuromodulators such as AMPT (100 mg/kg, i.p., a catecholamine synthesis inhibitor), prazosin (1 mg/kg, i.p., an α1-adrenoceptor antagonist), yohimbine (1 mg/kg, i.p., an α2-adrenoceptor antagonist) and with serotonergic neuromodulators such as PCPA (100 mg/kg, i.p., once daily for four consecutive days, a serotonin synthesis inhibitor,) and WAY100635 (0.1 mg/kg, s.c., a selective 5-HT1A receptor antagonist) significantly reversed the anti-immobility effect of α-asarone (20 mg/kg, i.p.). Taken together, our results suggest that the acute treatment with α-asarone elicited biphasic actions in the TST in which antidepressant-like effect was seen at relatively lower doses (15 and 20 mg/kg, i.p.) and depressive-like activity at relatively higher doses (50 and 100 mg/kg, i.p.). Furthermore, it has been revealed that the antidepressant-like effect of α-asarone could be mediated through both noradrenergic (α1 and α2 adrenoceptors) and serotonergic (particularly, 5-HT1A receptors) systems.

Dual Alpha2C/5HT1A Receptor Agonist Allyphenyline Induces Gastroprotection and Inhibits Fundic and Colonic Contractility.

Allyphenyline, a novel α2-adrenoceptor (AR) ligand, has been shown to selectively activate α2C-adrenoceptors (AR) and 5HT1A receptors, but also to behave as a neutral antagonist of α2A-ARs. We exploited this unique pharmacological profile to analyze the role of α2C-ARs and 5HT1A receptors in the regulation of gastric mucosal integrity and gastrointestinal motility. Gastric injury was induced by acidified ethanol in Wistar rats. Mucosal catalase and superoxide dismutase levels were measured by assay kits. The effect of allyphenyline on electrical field stimulation (EFS)-induced fundic and colonic contractions was determined in C57BL/6 mice. Intracerebroventricularly injected allyphenyline (3 and 15nmol/rat) dose dependently inhibited the development of mucosal damage, which was antagonized by ARC 239 (α2B/C-AR and 5HT1A receptor antagonist), (S)-WAY 100135 (selective 5HT1A receptor antagonist), and JP-1302 (selective α2C-AR antagonist). This protection was accompanied by significant elevation of mucosal catalase and superoxide dismutase levels. Allyphenyline (10(-9)-10(-5) M) also inhibited EFS-induced fundic contractions, which was antagonized by ARC 239 and (S)-WAY 100135, but not by JP-1302. Similar inhibition was observed in the colon; however, in this case only ARC 239 reduced this effect, while neither selective inhibition of α2C-ARs and 5HT1A receptors nor genetic deletion of α2A- and α2B-ARs influenced it. Activation of both central α2C-ARs and 5HT1A receptors contributes to the gastroprotective action of allyphenyline in rats. Its inhibitory effect on fundic contractions is mediated by 5HT1A receptors, but neither α2-ARs nor 5HT1A receptors take part in its inhibitory effect on colonic contractility in mice.