2,5-Dimethoxy-4-iodoamphetamine and altanserin induce region-specific shifts in dopamine and serotonin metabolization pathways in the rat brain.

PURPOSE: For understanding the neurochemical mechanism of neuropsychiatric conditions associated with cognitive deficits it is of major relevance to elucidate the influence of serotonin (5-HT) agonists and antagonists on memory function as well dopamine (DA) and 5-HT release and metabolism. In the present study, we assessed the effects of the 5-HT2A receptor agonist 2,5-dimethoxy-4-iodoamphetamine (DOI) and the 5-HT2A receptor altanserin (ALT) on object and place recognition memory and cerebral neurotransmitters and metabolites in the rat. METHODS: Rats underwent a 5-min exploration trial in an open field with two identical objects. After systemic injection of a single dose of either DOI (0.1 mg/kg), ALT (1 mg/kg) or the respectice vehicle (0.9 % NaCl, 50 % DMSO), rats underwent a 5-min test trial with one of the objects replaced by a novel one and the other object transferred to a novel place. Upon the assessment of object exploration and motor/exploratory behaviors, rats were sacrificed. DA, 5-HT and metabolite levels were analyzed in cingulate (CING), caudateputamen (CP), nucleus accumbens (NAC), thalamus (THAL), dorsal (dHIPP) and ventral hippocampus (vHIPP), brainstem and cerebellum with high performance liquid chromatography. RESULTS: DOI decreased rearing but increased head-shoulder motility relative to vehicle. Memory for object and place after both DOI and ALT was not different from vehicle. Network analyses indicated that DOI inhibited DA metabolization in CING, CP, NAC, and THAL, but facilitated it in dHIPP. Likewise, DOI inhibited 5-HT metabolization in CING, NAC, and THAL. ALT facilitated DA metabolization in the CING, NAC, dHIPP, vHIPP, and CER, but inhibited it in the THAL. Additionally, ALT facilitated 5-HT metabolization in NAC and dHIPP. CONCLUSIONS: DOI and ALT differentially altered the quantitative relations between the neurotransmitter/metabolite levels in the individual brain regions, by inducing region-specific shifts in the metabolization pathways. Findings are relevant for understanding the neurochemistry underlying DAergic and/or 5-HTergic dysfunction in neurological and psychiatric conditions.

Collaborative action between noradrenergic and serotoninergic systems in peripheral antinociception in mice.

Noradrenaline (NA) and serotonin (5-HT) induce nociception and antinociception. This antagonistic effect can be explained by the dose and type of activated receptors. We investigated the existence of synergism between the noradrenergic and serotonergic systems during peripheral antinociception. The paw pressure test was performed in mice that had increased sensitivity by intraplantar injection of prostaglandin E2 (PGE2). Noradrenaline (80 ng) administered intraplantarly induced an antinociceptive effect, that was reversed by the administration of selective antagonists of serotoninergic receptors 5-HT1B isamoltan, 5-HT1D BRL15572, 5-HT2A ketanserin, 5-HT3 ondansetron, but not by selective receptor antagonist 5-HT7 SB-269970. The administration of escitalopram, a serotonin reuptake inhibitor, potentiated the antinociceptive effect at a submaximal dose of NA. These results, indicate the existence of synergism between the noradrenergic and serotonergic systems in peripheral antinociception in mice.

The serotonin blocker Ketanserin reduces coral reef fish Ctenochaetus striatus aggressive behaviour during between-species social interactions.

A multitude of species engages in social interactions not only with their conspecifics but also with other species. Such interspecific interactions can be either positive, like helping, or negative, like aggressive behaviour. However, the physiological mechanisms of these behaviours remain unclear. Here, we manipulated the serotonin system, a well-known neurohormone for regulating intraspecific aggressive behaviour, to investigate its role in interspecific aggression. We tested whether serotonin blockade affects the aggressive behaviour of a coral reef fish species (Ctenochaetus striatus) that engages in mutualistic interactions with another species, the cleaner fish (Labroides dimidiatus). Although this mutualistic cleaning relationship may appear positive, cleaner fish do not always cooperate and remove ectoparasites from the other coral reef fish ("clients") but tend to cheat and bite the client's protective layer of mucus. Client fish thus often apply control mechanisms, like chasing, to deter their cleaner fish partners from cheating. Our findings show that blocking serotonin receptors 5-HT2A and 5-HT2C with ketanserin reduced the client fish's aggressive behaviour towards cleaner fish, but in the context where the latter did not cheat. These results are evidence of the involvement of serotonin in regulating aggressive behaviour at the between-species social interactions level. Yet, the direction of effect we found here is the opposite of previous findings using a similar experimental set-up and ecological context but with a different client fish species (Scolopsis bilineatus). Together, it suggests that serotonin's role in aggressive behaviour is complex, and at least in this mutualistic ecological context, its function is species-dependent. This warrants, to some extent, careful interpretations from single-species studies looking into the physiological mechanisms of social behaviour.

Mechanisms of 5-HT receptor antagonists in the regulation of fibrosis in a 3D human liver spheroid model.

Non-alcoholic steatohepatitis (NASH) is a major health problem leading to liver fibrosis and hepatocellular carcinoma, among other diseases, and for which there is still no approved drug treatment. Previous studies in animal models and in LX-2 cells have indicated a role for serotonin (5-HT) and 5-HT receptors in stellate cell activation and the development of NASH. In the current study, we investigated the extent to which these findings are applicable to a human NASH in vitro model consisting of human liver spheroids containing hepatocytes and non-parenchymal cells. Treatment of the spheroids with 5-HT or free fatty acids (FFA) induced fibrosis, whereas treatment of the spheroids with the 5-HT receptor antagonists ketanserin, pimavanserin, sarpogrelate, and SB269970 inhibited FFA-induced fibrosis via a reduction in stellate cell activation as determined by the expression of vimentin, TGF-ß1 and COL1A1 production. siRNA-based silencing of 5-HT2A receptor expression reduced the anti-fibrotic properties of ketanserin, suggesting a role for 5-HT receptors in general and 5-HT2A receptors in particular in the FFA-mediated increase in fibrosis in the human liver spheroid model. The results suggest a contribution of the 5-HT receptors in the development of FFA-induced human liver fibrosis with implications for further efforts in drug development.

Transport and inhibition mechanisms of human VMAT2.

Vesicular monoamine transporter 2 (VMAT2) accumulates monoamines in presynaptic vesicles for storage and exocytotic release, and has a vital role in monoaminergic neurotransmission1-3. Dysfunction of monoaminergic systems causes many neurological and psychiatric disorders, including Parkinson's disease, hyperkinetic movement disorders and depression4-6. Suppressing VMAT2 with reserpine and tetrabenazine alleviates symptoms of hypertension and Huntington's disease7,8, respectively. Here we describe cryo-electron microscopy structures of human VMAT2 complexed with serotonin and three clinical drugs at 3.5-2.8 Å, demonstrating the structural basis for transport and inhibition. Reserpine and ketanserin occupy the substrate-binding pocket and lock VMAT2 in cytoplasm-facing and lumen-facing states, respectively, whereas tetrabenazine binds in a VMAT2-specific pocket and traps VMAT2 in an occluded state. The structures in three distinct states also reveal the structural basis of the VMAT2 transport cycle. Our study establishes a structural foundation for the mechanistic understanding of substrate recognition, transport, drug inhibition and pharmacology of VMAT2 while shedding light on the rational design of potential therapeutic agents.

Treatment of acute-onset hypertension in pregnancy: A network meta-analysis of randomized controlled trials comparing anti-hypertensives and route of administration.

BACKGROUND: Consensus on the relative efficacy of available antihypertensive agents used in pregnancy is lacking. OBJECTIVE: To compare treatment success with antihypertensives and categorize by route of administration. SEARCH STRATEGY: MEDLINE, Embase, PubMed, Web of Science, Scopus, CINAHL, and clinicaltrials.gov were searched without date restriction. DATA COLLECTION: Peer-reviewed randomized controlled trials (RCTs) comparing pharmacologic agents used to treat hypertension in parturients were included. Evaluated treatment groups included IV-labetalol (BBIV), IV-hydralazine (DIV), oral-nifedipine (CCBPO), sublingual nifedipine (CCBSL), IV-calcium channel blocker (nonspecific)(CCBIV), IV-nitroglycerine (NTG), epoprostenol infusion (PRO), IV-ketanserin (5HT2B), IV-diazoxide (BZO), oral-nifedipine + methyldopa (CCBAG), oral-methyl-dopa (AAG), and oral prazosin (ABPO). ANALYSIS: Seventy-four studies (8324 patients) were eligible post PRISMA guidelines screening. Results were pooled using a Bayesian-approach for success of treatment (study defined target blood pressure), time to achieve target pressure, and neonatal intensive-care admissions. RESULTS: Treatment success (primary outcome, 55 trials with 5518 patients) was analyzed. Surface under the cumulative ranking curve (SUCRA) was categorized for 13 drugs, CCBPO (0.84) followed by CCBSL (0.78) were most likely to be effective in achieving target blood pressure. After sub-grouping by presence/absence of preeclampsia, CCB-PO ranked highest for both [(0.82) vs. (0.77), respectively]. Serotonin antagonists (0.99) and nitroglycerin (0.88) ranked highest for time to target pressure. NICU admissions were lowest for alpha-2 agonists (0.89), followed by BB PO (0.82) and hydralazine IV (0.49). CONCLUSION: Oral calcium-channel blockers ranked highest for treatment success. Ketanserin achieved target blood pressure fastest, warranting additional research. The results should be interpreted with caution as SUCRA values may not indicate whether the differences between interventions have clinically meaningful effect sizes.

Effects of Chronic Combined Treatment with Ketanserin and Fluoxetine in B6.CBA-D13Mit76C Recombinant Mice with Abnormal 5-HT1A Receptor Functional Activity.

The recombinant B6.CBA-D13Mit76C mouse strain is characterized by an altered sensitivity of 5-HT1A receptors and upregulated 5-HT1A gene transcription. Recently, we found that in B6.CBA-D13Mit76C mice, chronic fluoxetine treatment produced the pro-depressive effect in a forced swim test. Since 5-HT2A receptor blockade may be beneficial in treatment-resistant depression, we investigated the influence of chronic treatment (14 days, intraperitoneally) with selective 5-HT2A antagonist ketanserin (0.5 mg/kg), fluoxetine (20 mg/kg), or fluoxetine + ketanserin on the behavior, functional activity of 5-HT1A and 5-HT2A receptors, serotonin turnover, and transcription of principal genes of the serotonin system in the brain of B6.CBA-D13Mit76C mice. Ketanserin did not reverse the pro-depressive effect of fluoxetine, while fluoxetine, ketanserin, and fluoxetine + ketanserin decreased the functional activity of 5-HT1A receptors and Htr1a gene transcription in the midbrain and hippocampus. All tested drug regimens decreased the mRNA levels of Slc6a4 and Maoa in the midbrain. These changes were not accompanied by a significant shift in the levels of serotonin and its metabolite 5-HIAA. Notably, ketanserin upregulated enzymatic activity of tryptophan hydroxylase 2 (TPH2). Thus, despite some benefits (reduced Htr1a, Slc6a4, and Maoa transcription and increased TPH2 activity), prolonged blockade of 5-HT2A receptors failed to ameliorate the adverse effect of fluoxetine in the case of abnormal functioning of 5-HT1A receptors.

A new computational approach, based on images trajectories, to identify the subjacent heterogeneity of sperm to the effects of ketanserin.

The identification of kinematic subpopulations is of paramount importance to understanding the biological nature of the sperm heterogeneity. Nowadays, the data of motility parameters obtained by a computer-assisted sperm analysis (CASA) system has been used as input to distinct algorithms to identify kinematic subpopulations. In contrast, the images of the trajectories were depicted only as examples of the patterns of motility in each subpopulation. Here, python code was written to reconstruct the images of trajectories, from their coordinates, then the images of trajectories were used as input to a machine learning clustering algorithm of classification, and the subpopulations were described statistically by the motility parameters. Finally, the images of trajectories in each subpopulation were displayed in a way we called Pollock plots. Semen samples of boar sperm were treated with distinct concentrations of ketanserin (an antagonist of the 5-HT2 receptor of serotonin) and untreated samples were used as a control. The motility of sperm in each sample was analyzed at 0 and 30 min of incubation. Six subpopulations were found. The subpopulation 2 presented the highest values of velocities at 0 or 30 min. After 30 min of incubation, the ketanserin increased the values of the curvilinear velocity at high concentrations, whereas the linearity and the straight velocity decreased. Our computational model permits better identification of the kinematic subpopulations than the traditional approach and provides insights onto the heterogeneity of the response to ketanserin; thus, it could significantly impact the research on the relationship between sperm heterogeneity-fertility.

Binary to ternary drug-drug molecular adducts of the antihypertensive drug ketanserin (KTS) with advanced physicochemical properties.

Focusing on a reliable supramolecular synthon approach, novel molecular salts of the antihypertensive medication ketanserin (KTS) with aromatic carboxylic acid derivatives (benzoic acid (BA), 2-hydroxybenzoic acid (2-HBA), and 2,5-dihydroxybenzoic acid (2,5-DHBA)) are reported. Binary salts of KTS with the respective salt former were obtained via solvent-assisted grinding followed by solution crystallization. Salt production was confirmed through crystal structure investigations that revealed proton transfer from the carboxylic acid group of the salt former to the piperidine nitrogen atom of KTS. A rigorous investigation of the crystal packing of novel binary salts of KTS inspired the construction of ternary adducts, and a ternary crystalline product was subsequently identified using milrinone (MLN), another cardiotonic drug. According to our knowledge, this is the first instance of a dual-drug ternary co-crystal combining both antihypertensive drugs. In order to evaluate the impacts of co-crystallization on the in vitro release behaviour of binary and ternary adducts, solubility tests for the cocrystal were carried out under a variety of physiological pH conditions. The results indicate that, in contrast to the parent drug and binary adducts, the solubility rate of the ternary adducts is significantly increased. Finally, the stability of the synthesised adduct was evaluated under a range of conditions, including temperature (40 ± 1 °C), humidity (90% ± 5% RH, 25 °C) and various solvents media, and it was established that they have good stability. We anticipate that the present findings will work with a wide range of medication combinations, providing a potential new approach to create multi-drug systems for cardiovascular disease.

Acute psilocybin enhances cognitive flexibility in rats.

Psilocybin has been shown to improve symptoms of depression and anxiety when combined with psychotherapy or other clinician-guided interventions. To understand the neural basis for this pattern of clinical efficacy, experimental and conceptual approaches that are different than traditional laboratory models of anxiety and depression are needed. A potential novel mechanism is that acute psilocybin improves cognitive flexibility, which then enhances the impact of clinician-assisted interventions. Consistent with this idea, we find that acute psilocybin robustly improves cognitive flexibility in male and female rats using a task where animals switched between previously learned strategies in response to uncued changes in the environment. Psilocybin did not influence Pavlovian reversal learning, suggesting that its cognitive effects are selective to enhanced switching between previously learned behavioral strategies. The serotonin (5HT) 2 A receptor antagonist ketanserin blocked psilocybin's effect on set-shifting, while a 5HT2C-selective antagonist did not. Ketanserin alone also improved set-shifting performance, suggesting a complex relationship between psilocybin's pharmacology and its impact on flexibility. Further, the psychedelic drug 2,5-Dimethoxy-4-iodoamphetamine (DOI) impaired cognitive flexibility in the same task, suggesting that this effect of psilocybin does not generalize to all other serotonergic psychedelics. We conclude that the acute impact of psilocybin on cognitive flexibility provides a useful behavioral model to investigate its neuronal effects relevant to its positive clinical outcome.

Effects of Ketanserin, M100907 and Olanzapine on hallucinogenic like action induced by 2,5-dimethoxy-4-methylamphetamine.

2,5-dimethoxy-4-methylamphetamine (DOM) is a kind of hallucinogen of phenylalkylamine. Psychedelic effects mainly include audiovisual synesthesia, complex imagery, disembodiment etc. that can impair control and cognition leading to adverse consequences such as suicide. By now, there are no specific drugs regarding the management of classic hallucinogen use clinically. We evaluated the effects of three 5-HT 2A receptor antagonists ketanseirn, M100907 and olanzapine on hallucination-like behavior in therapeutic and preventive administration with male C57BL/6J mice. Two models were used to evaluate the therapeutic potential of antagonists, one is head-twitch response (HTR) and the other is locomotion. Effects of ketanserin, M100907 and olanzapine on DOM-induced HTR were studied in preventive and therapeutic administration, respectively. In the preventive administration, the ID 50 values of ketanseirn, M100907 and olanzapine were 0.4 mg/kg, 0.005 mg/kg and 0.25 mg/kg. In the therapeutic administration, the ID 50 values of ketanseirn, M100907 and olanzapine were 0.04 mg/kg, 0.005 mg/kg and 0.03 mg/kg. Secondly, locomotor activity induced by DOM was performed to further evaluate the efficacy of three compounds. In locomotion, M100907(0.005 mg/kg) whenever in preventive or therapeutic administration, reduced the increase of movement distance induced by DOM. Although ketanserin (0.4 mg/kg) in the preventive administration also decreased the movement distance induced by DOM, it was alone administrated to influence the locomotor activity. Through HTR and locomotion, we compared the efficacy and latent side effects of ketanserin, M100907 and olanzapine against hallucinogenic like action induced by DOM. Our study provided additional experimental evidence on specific therapeutic drugs against hallucinogenic behavior induce by representative hallucinogen DOM.

Memory and anxiety-like behavior of rats in the plus-maze discriminative avoidance task: Role of serotonergic transmission in the basolateral amygdala.

Optimal levels of anxiety are critical to memory consolidation, but maladaptive anxiety can disrupt memory acquisition. Serotonergic activity within the amygdala influences both anxiety-like behavior and aversive memory consolidation. To evaluate the effects of serotoninergic manipulations within the basolateral amygdala (BLA) on anxiety-like behavior and aversive memory in rats tested in the plus-maze discriminative avoidance task (PMDAT). The PMDAT investigates aversive memory and anxiety-like behavior simultaneously in rodents. Three-month-old male Wistar rats received bilateral infusions (1 µL per side) of saline, 8-OH-DPAT (5-HT1 agonist; 10 nmol), WAY100135 (5-HT1 antagonist; 0.9 nmol), ketanserine (5-HT 2 antagonist; 10 nmol), or fluoxetine (serotonin reuptake inhibitor; 1.6 nmol) into the BLA and were submitted to PMDAT training session 15 min later. In the test, 24 hr later, animals were re-exposed to the apparatus without the infusion of drugs, and aversive memory was evaluated. (a) 8-OH-DPAT did not affect memory or anxiety, but impaired avoidance behavior toward the aversive arm during training; (b) fluoxetine, WAY100135 and ketanserin impaired memory formation; (c) ketanserin decreased anxiety-like behavior; and (d) none of the treatments induced motor changes. The results showed that an increase in serotonin (5-HT) availability or the blockade of 5HT1A and 5HT2A BLA receptors impaired aversive memory formation. However, only 5HT2A receptor antagonism induced anxiolytic effects. Thus, both memory and anxiety-like behavior can be modified by changes in serotonergic transmission in the basolateral amygdala, but the effects on both phenomena seem to be mediated by different mechanisms related to serotonergic transmission. (PsycInfo Database Record (c) 2023 APA, all rights reserved).

Ketanserin Reverses the Acute Response to LSD in a Randomized, Double-Blind, Placebo-Controlled, Crossover Study in Healthy Participants.

BACKGROUND: Lysergic acid diethylamide (LSD) is currently being investigated in psychedelic-assisted therapy. LSD has a long duration of acute action of 8-11 hours. It produces its acute psychedelic effects via stimulation of the serotonin 5-hydroxytryptamine-2A (HT2A) receptor. Administration of the 5-HT2A antagonist ketanserin before LSD almost fully blocks the acute subjective response to LSD. However, unclear is whether ketanserin can also reverse the effects of LSD when administered after LSD. METHODS: We used a double-blind, randomized, placebo-controlled, crossover design in 24 healthy participants who underwent two 14-hour sessions and received ketanserin (40 mg p.o.) or placebo 1 hour after LSD (100 µg p.o.). Outcome measures included subjective effects, autonomic effects, acute adverse effects, plasma brain-derived neurotrophic factor levels, and pharmacokinetics up to 12 hours. RESULTS: Ketanserin reversed the acute response to LSD, thereby significantly reducing the duration of subjective effects from 8.5 hours with placebo to 3.5 hours. Ketanserin also reversed LSD-induced alterations of mind, including visual and acoustic alterations and ego dissolution. Ketanserin reduced adverse cardiovascular effects and mydriasis that were associated with LSD but had no effects on elevations of brain-derived neurotrophic factor levels. Ketanserin did not alter the pharmacokinetics of LSD. CONCLUSIONS: These findings are consistent with an interaction between ketanserin and LSD and the view that LSD produces its psychedelic effects only when occupying 5-HT2A receptors. Ketanserin can effectively be used as a planned or rescue option to shorten and attenuate the LSD experience in humans in research and LSD-assisted therapy. TRIAL REGISTRY: ClinicalTrials.gov (NCT04558294).

Spontaneous head twitches in aged rats: behavioral and molecular study.

RATIONALE: We have discovered that rats at the age of 18 months begin to twitch their heads spontaneously (spontaneous head twitching, SHT). To date, no one has described this phenomenon. OBJECTIVES: The purpose of this study was to characterize SHT pharmacologically and to assess some possible mechanisms underlying SHT. METHODS: Wistar male rats were used in the study. Animals at the age of 18 months were qualified as HSHT (SHT ≥ 7/10 min observations) or LSHT (SHT < 7/10 min observations). Quantitative real-time PCR with TaqMan low-density array (TLDA) approach was adopted to assess the mRNA expression of selected genes in rat's hippocampus. RESULTS: HSHT rats did not differ from LSHT rats in terms of survival time, general health and behavior, water intake, and spontaneous locomotor activity. 2,5-dimethoxy-4-iodoamphetamine (DOI) at a dose of 2.5 mg/kg increased the SHT in HSHT and LSHT rats, while ketanserin dose-dependently abolished the SHT in the HSHT rats. The SHT was reduced or abolished by olanzapine, clozapine, risperidone, and pimavanserin. All these drugs have strong 5-HT2A receptor-inhibiting properties. Haloperidol and amisulpride, as antipsychotic drugs with a mostly dopaminergic mechanism of action, did not influence SHT. Similarly, escitalopram did not affect SHT. An in-depth gene expression analysis did not reveal significant differences between the HSHT and the LSHT rats. CONCLUSIONS: SHT appears in some aging rats (about 50%) and is permanent over time and specific to individuals. The 5-HT2A receptor strongly controls SHT. HSHT animals can be a useful animal model for studying 5-HT2A receptor ligands.

Presynaptic 5-HT2A-mGlu2/3 Receptor-Receptor Crosstalk in the Prefrontal Cortex: Metamodulation of Glutamate Exocytosis.

The glutamatergic nerve endings of a rat prefrontal cortex (PFc) possess presynaptic 5-HT2A heteroreceptors and mGlu2/3 autoreceptors, whose activation inhibits glutamate exocytosis, and is measured as 15 mM KCl-evoked [3H]D-aspartate ([3H]D-asp) release (which mimics glutamate exocytosis). The concomitant activation of the two receptors nulls their inhibitory activities, whereas blockade of the 5-HT2A heteroreceptors with MDL11,939 (1 µM) strengthens the inhibitory effect elicited by the mGlu2/3 receptor agonist LY329268 (1 µM). 5-HT2A receptor antagonists (MDL11,939; ketanserin; trazodone) amplify the impact of low (3 nM) LY379268. Clozapine (0.1-10 µM) mimics the 5-HT2A agonist (±) DOI and inhibits the KCl-evoked [3H]D-asp overflow in a MDL11,939-dependent fashion, but does not modify the (±) DOI-induced effect. mGlu2 and 5-HT2A proteins do not co-immunoprecipitate from synaptosomal lysates, nor does the incubation of PFc synaptosomes with MDL11,939 (1 µM) or clozapine (10 µM) modify the insertion of mGlu2 subunits in synaptosomal plasma membranes. In conclusion, 5-HT2A and mGlu2/3 receptors colocalize, but do not physically associate, in PFc glutamatergic terminals, where they functionally interact in an antagonist-like fashion to control glutamate exocytosis. The mGlu2/3-5-HT2A metamodulation could be relevant to therapy for central neuropsychiatric disorders, including schizophrenia, but also unveil cellular events accounting for their development, which also influence the responsiveness to drugs regimens.

Contrasting effects of DOI and lisuride on impulsive decision-making in delay discounting task.

RATIONALE: The 5-HT2A receptor is the major target of classic hallucinogens. Both DOI (2,5-dimethoxy-4-iodoamphetamine) and lisuride act at 5-HT2A receptors, and lisuride shares comparable affinity with DOI and acts as a partial agonist at 5-HT2A receptors. However, not like DOI, lisuride lacks hallucinogenic properties. Impulsive decision-making refers to the preference for an immediate small reinforcer (SR) over a delayed large reinforcer (LR). OBJECTIVES: The current study aims to compare the effects of DOI and lisuride on impulsive decision-making and further to investigate the possible receptor mechanisms responsible for the actions of the two drugs. METHODS: Impulsive decision-making was evaluated in male Sprague-Dawley rats by the percentage of choice for the LR in delay discounting task (DDT). Delay to the LR changed in an ascending order (0, 4, 8, 16, and 32 s) across one session. RESULTS: DOI (0.5 and 1.0 mg/kg) increased impulsive decision-making, and the effects of DOI (1.0 mg/kg) were blocked by the 5-HT2A receptor antagonist ketanserin (1.0 mg/kg) rather than the 5-HT2C receptor antagonist SB-242084 (1.0 mg/kg). Contrarily, lisuride (0.1, 0.3, and 0.5 mg/kg) decreased impulsive decision-making. The effects of lisuride (0.3 mg/kg) were not antagonized by ketanserin (1.0 mg/kg), selective 5-HT1A antagonist WAY-100635 (1.0 mg/kg), or selective dopamine D4 receptor antagonist L-745870 (1.0 mg/kg) but were attenuated by the selective dopamine D2/D3 receptor antagonist tiapride (40 mg/kg). CONCLUSIONS: DOI and lisuride have contrasting effects on impulsive decision-making via distinct receptors. DOI-induced increase of impulsivity is mediated by the 5-HT2A receptor, while lisuride-induced inhibition of impulsivity is regulated by the dopamine D2/D3 receptor.

Vasoconstrictor and hemodynamic effects of a methanolic extract from Rhinella marina toad poison.

Rhinella marina toad is abundant in Brazil. Its poison contains cardiac glycosides called bufadienolides, which are extensively investigated for their bioactivity. Our aim was to characterize the vasoactivity of Rhinella marina poison (RmP) on the aorta of male Wistar rats. For this, the RmP was first collected and processed to obtain an alcoholic extract. To determine cardiovascular effects of RmP, we performed in vivo tests by administering RmP intravenously in doses of 0.1-0.8 mg/kg. Vascular reactivity was also performed through concentration-response curves to RmP (10 ng/mL to 200 µg/mL) in aortic segments with and without endothelium. RmP induced a concentration-dependent contraction in rat aorta which was partly endothelium-mediated. Nitric oxide contributes with this response in view that incubation with L-NAME increased the contractile response. Additionally, treatment with indomethacin [cyclooxygenase, (COX) inhibitor], nifedipine (L-type voltage-gated calcium channels blocker), and BQ-123 (ETA receptors antagonist) decreased maximum response, and ketanserin (5-HT2 receptors antagonist) decreased pEC50, suggesting active participation of these pathways in the contractile response. On the other hand, apocynin (NADPH oxidase inhibitor) did not alter contractility. Incubation with prazosin (α1-adrenergic receptor antagonist) abolished the contractile response, suggesting that the RmP-induced contraction is dependent on the adrenergic pathway. In the Na+/K+ ATPase protocol, a higher Emax was observed in the RmP experimental group, suggesting that RmP potentiated Na+/K+ATPase hyperpolarizing response. When this extract was injected (i.v.) in vivo, increase in blood pressure and decrease in heart rate were observed. The results were immediate and transitory, and occurred in a dose-dependent manner. Overall, these data suggest that the poison extract of R. marina toad has an important vasoconstrictor action and subsequent vasopressor effects, and its use can be investigated to some cardiovascular disorders.

Role of 5-HT2A Receptor in Modulating Glutamatergic Activity in the Ventrolateral Orbital Cortex: Implication in Trigeminal Neuralgia.

5-HT2A receptors (5-HT2ARs) are widely expressed in the central nervous system, including in the ventrolateral orbital cortex (VLO). The VLO is an important cortical component for pain processing. Brain 5-HT2ARs are implicated in both pro- and anti- nociceptive functions. However, the roles of 5-HT2ARs in the VLO in trigeminal neuralgia and neuronal synaptic function remain to be understood. We used chronic constriction injury of infraorbital nerve (IoN-CCI) model and shRNA mediated gene knockdown in mice to investigate the role of 5-HT2ARs in the VLO in trigeminal neuralgia. We found that knockdown of 5-HT2ARs in the VLO aggravated spontaneous pain and mechanical allodynia in mice after IoN-CCI. At the synaptic level, decreasing 5-HT2AR expression by shRNA or inhibition of 5-HT2AR activity by its antagonist ketanserin decreased the frequency and amplitude of spontaneous excitatory postsynaptic currents (sEPSCs) of the neurons in the VLO, whereas 5-HT2AR partial agonist 2,5-Dimethoxy-4-iodoamphetamine (DOI) enhanced sEPSCs of the neurons in the VLO. In summary, 5-HT2ARs in the VLO modulate the trigeminal pain by regulating neuronal glutamatergic activity.

Serotonin Receptor 5-HT2A Regulates TrkB Receptor Function in Heteroreceptor Complexes.

Serotonin receptor 5-HT2A and tropomyosin receptor kinase B (TrkB) strongly contribute to neuroplasticity regulation and are implicated in numerous neuronal disorders. Here, we demonstrate a physical interaction between 5-HT2A and TrkB in vitro and in vivo using co-immunoprecipitation and biophysical and biochemical approaches. Heterodimerization decreased TrkB autophosphorylation, preventing its activation with agonist 7,8-DHF, even with low 5-HT2A receptor expression. A blockade of 5-HT2A receptor with the preferential antagonist ketanserin prevented the receptor-mediated downregulation of TrkB phosphorylation without restoring the TrkB response to its agonist 7,8-DHF in vitro. In adult mice, intraperitoneal ketanserin injection increased basal TrkB phosphorylation in the frontal cortex and hippocampus, which is in accordance with our findings demonstrating the prevalence of 5-HT2A-TrkB heteroreceptor complexes in these brain regions. An expression analysis revealed strong developmental regulation of 5-HT2A and TrkB expressions in the cortex, hippocampus, and especially the striatum, demonstrating that the balance between TrkB and 5-HT2A may shift in certain brain regions during postnatal development. Our data reveal the functional role of 5-HT2A-TrkB receptor heterodimerization and suggest that the regulated expression of 5-HT2A and TrkB is a molecular mechanism for the brain-region-specific modulation of TrkB functions during development and under pathophysiological conditions.

Death-Associated Protein Kinase 3 Inhibitors Identified by Virtual Screening for Drug Discovery in Cancer and Hypertension.

Death-associated protein kinase 3 (DAPK3) is a serine/threonine protein kinase that regulates apoptosis, autophagy, transcription, and actin cytoskeleton reorganization. DAPK3 induces morphological alterations in apoptosis when overexpressed, and it is considered a potential drug target in antihypertensive and anticancer drug development. In this article, we report new findings from a structure-guided virtual screening for discovery of phytochemicals that could modulate the elevated expression of DAPK3, and with an eye to anticancer drug discovery. We used the Indian Medicinal Plants, Phytochemistry and Therapeutics (IMPPAT), a curated database, as part of the methodology. The potential initial hits were identified based on their physicochemical properties and binding affinity toward DAPK3. Subsequently, various filters for drug likeness followed by interaction analysis and molecular dynamics (MD) simulations for 100 nsec were performed to explore the conformational sampling and stability of DAPK3 with the candidate molecules. Notably, the data from all-atom MD simulations and principal component analysis suggested that DAPK3 forms stable complexes with ketanserin and rotenone. In conclusion, this study supports the idea that ketanserin and rotenone bind to DAPK3, and show stability, which can be further explored as promising scaffolds in drug development and therapeutics innovation in clinical contexts such as hypertension and various types of cancer.