Effects of serta and sertb knockout on aggression in zebrafish (Danio rerio).

Zebrafish (Danio rerio) are unusual in having two paralogues of the serotonin re-uptake transporter (Sert), slc6a4a (serta) and slc6a4b (sertb), the transporter that serves in serotonin re-uptake from a synapse into the pre-synaptic cell or in serotonin uptake from the extracellular milieu into cells in the peripheral tissues. To address a knowledge gap concerning the specific roles of these paralogues, we used CRISPR/Cas9 technology to generate zebrafish knockout lines predicted to lack functional expression of Serta or Sertb. The consequences of loss-of-function of Serta or Sertb were assessed at the gene expression level, focusing on the serotonergic signalling pathway, and at the behaviour level, focusing on aggression. Whereas serta mRNA was expressed in all tissues examined, with high expression in the heart, gill and brain, only the brain displayed substantial sertb mRNA expression. In both serta-/- and sertb-/- fish, changes in transcript abundances of multiple components of the serotonin signalling pathway were detected, including proteins involved in serotonin synthesis (tph1a, tph1b, tph2, ddc), packaging (vmat2) and degradation (mao), and serotonin receptors (htr1aa, htr1ab). Using a mirror aggression test, serta-/- male but not female fish exhibited greater aggression than wildtype fish. However, both male and female sertb-/- fish displayed less aggression than their wildtype counterparts. These differences in behaviour between serta-/- and sertb-/- individuals hold promise for increasing our understanding of the neurophysiological basis of aggression in zebrafish.

Switch from fight-flight to freeze-hide: The impacts of severe stress and brain serotonin on behavioral adaptations in flatfish.

Animals often experience changes in their environment that can be perceived as stressful. Previous evidence indicates that different individuals may have distinct stress responses. The role of serotonin (5-HT) in stress adaptation is well established, but its relationship with different defense strategies and the persistence of physiological and behavioral responses in different individuals during repeated acute stress remain unclear. In this study, using olive flounder (Paralichthys olivaceus) as a model, we analyzed the relationship between boldness and neurotransmitter 5-HT activity. We found that 5-HT suppression with 5-HT synthesis inhibitor p-chlorophenylalanine (pCPA) and 5-HT receptor subtype 1A (5-HT1A) antagonist WAY-100635 increased their oxygen consumption rates and the boldness of shy individuals. We determined the metabolic and behavioral changes in bold and shy individuals to repeated acute stress. The results suggest that bold individuals switch on passive "energy-saving" personality by changing their defense behavior from "fight-flight" to "freeze-hide" during a threat encounter, which manifests high behavioral plasticity. Both behavioral types decreased their spontaneous activity levels, which were also strengthened by limiting metabolic rate. Interestingly, treatment with pCPA and WAY-100635 before stress procedure attenuated stress and increased the boldness across diverse behavioral types. This study provides the initial empirical evidence of how perception of stress impacts both individual defense behavior and personality in this species. These findings can enhance our comprehension of individual variability and behavioral plasticity in animals, thereby improving our ability to develop effective adaptive management strategies.

The Serotonin-Mediated Anti-Allodynic Effect of Yokukansan on Paclitaxel-Induced Neuropathic Pain.

Refractory peripheral neuropathy can occur as a side effect in 60-70% of patients receiving Paclitaxel (PTX). Yokukansan (YKS) is a Japanese herbal medicine reported to have analgesic properties for entrapment nerve injuries. Therefore, we investigated the anti-allodynic effect of Yokukansan on Paclitaxel-induced neuropathic pain. All experiments used 6-week-old male Sprague Dawley rats. Mechanical allodynia was evaluated using a dynamic plantar aesthesiometer. A mobile touch-stimulator unit applied progressively increasing force to the mid-plantar region of the hind paw in a vertical direction until the animal withdrew its paw. This was carried out before the Paclitaxel administration and during the first, second, third, and fourth weeks. Using a rat model of PTX-induced neuropathic pain (PTX rat), we injected PTX (intraperitoneally, 2 mg/kg) five times every 2 days. Using the dynamic plantar test, we evaluated the anti-allodynic effect of YKS (orally administered, 1 g/kg). YKS administration on a daily basis significantly enhanced the withdrawal threshold in PTX rats and reduced the expression level of activated microglia immunostaining with Iba1, a specific marker for microglia. The intrathecal administration of WAY-100635 (5-hydroxytryptamine [5-HT]1A receptor antagonist) and Ketanserin (5-HT2A/2C receptor antagonist) inhibited the protective effects of YKS. YKS exhibited an anti-allodynic effect in a rodent model of PTX-induced neuropathic pain by reducing the sensitivity to pain stimuli. These results suggest that Yokukansan may activate 5-HT receptors in the spinal cord, mediating Paclitaxel-induced neuropathic pain.

Antidepressant Effects of Essential Oils: A Review of the Past Decade (2012-2022) and Molecular Docking Study of Their Major Chemical Components.

Depression is a mental disorder that affects more than 300 million people worldwide. The medications available for treatment take a long time to exhibit therapeutic results and present several side effects. Furthermore, there is a decrease in the quality of life of people suffering from this affliction. Essential oils are traditionally used to relieve the symptoms of depression due to the properties of the constituents of these oils to cross the blood-brain barrier acting on depression-related biological receptors associated with reduced toxicity and side effects. In addition, compared to traditional drugs, they have several administration forms. This review provides a comprehensive assessment of studies on plants whose essential oil has exhibit antidepressant activity in the past decade and the mechanism of action of the major components and models tested. An additional in silico study was conducted with the frequent compounds in the composition of these essential oils, providing a molecular approach to the mechanism of action that has been reported in the past decade. This review is valuable for the development of potential antidepressant medications in addition to providing a molecular approach to the antidepressant mechanism of action of the major volatile compounds that have been reported in the past decade.

Synthesis and biological evaluation of novel antipsychotic trans-4-(2-(1,2,4,5-tetrahydro-3H-benzo[d]azepin-3-yl)ethyl)cyclohexan-1-amine derivatives targeting dopamine/serotonin receptor subtypes.

In this study, a series of trans-4-(2-(1,2,4,5-tetrahydro-3H-benzo[d]azepin-3-yl)ethyl)cyclohexan-1-amine derivatives as potential antipsychotics were synthesized and biologically evaluated to discover potential antipsychotics with good drug target selectivity. The preliminary structure-activity relationship was discussed, and optimal compound 12a showed both nanomolar affinity for D2/D3/5-HT1A/5-HT2A receptors and weak α1 and H1 receptor binding affinity. In addition, 12a was metabolically stable in vitro, displayed micromolar affinity for the hERG channel, and exhibited antipsychotic efficacy in the animal model of locomotor-stimulating effects of phencyclidine.

Serotonin 2A receptor function and depression-like behavior in rats model of hypothyroidism.

Hypothyroidism causes somatic, psychosocial and affective psychosis, including depression-like behaviors. In this study, (hypothyroidism group; HP group) adult male Sprague Dawley (SD) rats were induced to hypothyroidism after 5 weeks of exposure to 0.05% propylthiouracil (PTU) in potable water, control animals (CON group) were given the same amount of water. The following behavioral experiments were conducted, respectively: open-field test (OFT), forced swimming test (FST), tail suspension test (TST). TT[Formula: see text] and TT[Formula: see text] levels were measured after the behavior tests and the expression levels of 5-HT[Formula: see text] receptor and 5-HT[Formula: see text] receptor proteins were analyzed in the hippocampus and prefrontal cortex. The level of TT[Formula: see text] and TT[Formula: see text] in the HP group rats was much lower than that in the CON group. The hypothyroid rats also showed weight loss, much longer immobility time in tail suspension test and forced swimming test. Besides, 5 weeks of PTU administration was associated with significantly decreased expression levels of 5-HT[Formula: see text] receptor and 5-HT[Formula: see text] receptor proteins compared with control group, which were significantly negatively correlated with immobility time in FST and TST. In conclusion, our results suggest that hypothyroidism induces depressive behaviors through the influence of the serotonin system, and the decreased expression of the 5-HT[Formula: see text] receptor is an important cause of the depressive behaviors in hypothyroidism.

Research progress in biological activities of succinimide derivatives.

Succinimides are well recognized heterocyclic compounds in drug discovery which produce diverse therapeutically related applications in pharmacological practices. Researches in medicinal chemistry field have isolated and synthesized succinimide derivatives with multiple medicinal properties including anticonvulsant, anti-inflammatory, antitumor and antimicrobial agents, 5-HT receptor ligands and enzyme inhibitors. Simultaneously, SAR (Structure-Activity Relationship) analysis has been gradually possessed, along with a great deal of derivatives have been derived for potential targets. In this article, we comprehensively summarize the biological activities and SAR for succinimide derivatives, along with the featuring bioactive molecules reported in patents, wishing to provide an overall retrospect and prospect on the succinimide analogues.

Distinct Effects of Escitalopram and Vortioxetine on Astroglial L-Glutamate Release Associated with Connexin43.

It has been established that enhancement of serotonergic transmission contributes to improvement of major depression; however, several post-mortem studies and experimental depression rodent models suggest that functional abnormalities of astrocytes play important roles in the pathomechanisms/pathophysiology of mood disorders. Direct effects of serotonin (5-HT) transporter inhibiting antidepressants on astroglial transmission systems has never been assessed in this context. Therefore, to explore the effects of antidepressants on transmission associated with astrocytes, the present study determined the effects of the selective 5-HT transporter inhibitor, escitalopram, and the 5-HT partial agonist reuptake inhibitor, vortioxetine, on astroglial L-glutamate release through activated hemichannels, and the expression of connexin43 (Cx43), type 1A (5-HT1AR) and type 7 (5-HT7R) 5-HT receptor subtypes, and extracellular signal-regulated kinase (ERK) in astrocytes using primary cultured rat cortical astrocytes in a 5-HT-free environment. Both escitalopram and 5-HT1AR antagonist (WAY100635) did not affect basal astroglial L-glutamate release or L-glutamate release through activated hemichannels. Subchronic (for seven days) administrations of vortioxetine and the 5-HT7R inverse agonist (SB269970) suppressed both basal L-glutamate release and L-glutamate release through activated hemichannels, whereas 5-HT1AR agonist (BP554) inhibited L-glutamate release through activated hemichannels, but did not affect basal L-glutamate release. In particular, WAY100635 did not affect the inhibitory effects of vortioxetine on L-glutamate release. Subchronic administration of vortioxetine, BP554 and SB269970 downregulated 5-HT1AR, 5-HT7R and phosphorylated ERK in the plasma membrane fraction, but escitalopram and WAY100635 did not affect them. Subchronic administration of SB269970 decreased Cx43 expression in the plasma membrane but did not affect the cytosol; however, subchronic administration of BP554 increased Cx43 expression in the cytosol but did not affect the plasma membrane. Subchronic vortioxetine administration increased Cx43 expression in the cytosol and decreased it in the plasma membrane. WAY100635 prevented an increased Cx43 expression in the cytosol induced by vortioxetine without affecting the reduced Cx43 expression in the plasma membrane. These results suggest that 5-HT1AR downregulation probably increases Cx43 synthesis, but 5-HT7R downregulation suppresses Cx43 trafficking to the plasma membrane. These results also suggest that the subchronic administration of therapeutic-relevant concentrations of vortioxetine inhibits both astroglial L-glutamate and Cx43 expression in the plasma membrane via 5-HT7R downregulation but enhances Cx43 synthesis in the cytosol via 5-HT1AR downregulation. This combination of the downregulation of 5-HT1AR, 5-HT7R and Cx43 in the astroglial plasma membrane induced by subchronic vortioxetine administration suggest that astrocytes is possibly involved in the pathophysiology of depression.

Identification, characterization, and expression analysis of a serotonin receptor involved in the reproductive process of the Pacific abalone, Haliotis discus hannai.

Serotonin receptor (5-HT) is a biogenic amine acting as a neurotransmitter and neuromodulator that mediates various aspects of reproduction and gametogenesis. The full-length nucleotide sequence of Haliotis discus hannai encodes a protein of 417 amino acids with a predicted molecular mass of 46.54 kDa and isoelectric point of 8.94. The structural profile of 5-HTHdh displayed key features of G protein-coupled receptors, including seven hydrophobic transmembrane domains, putative N-linked glycosylation sites, and several phosphorylation consensus motifs. It shares the highest homology of its amino acid sequence with the 5-HT receptor from Haliotis asinina, and to lesser extent of human 5-HT receptor. The cloned sequence possesses two cysteine residues (Cys-115 and Cys-193), which are likely to form a disulfide bond. Phylogenetic comparison with other known 5-HT receptor genes revealed that the 5-HTHdh is most closely related to the 5-HTHa receptor. The three-dimensional structure of the 5-HTHdh showed multiple alpha helices which is separated by a helix-loop-helix (HLH) structure. Quantitative PCR demonstrated that the receptor mRNA was predominantly expressed in the pleuropedal ganglion. Significant differences in the transcriptional activity of the 5-HTHdh gene were observed in the ovary at the ripening stage. An exclusive expression was detected in pleuropedal ganglion, testis, and ovary at higher effective accumulative temperature (1000 °C). In situ hybridization showed that the 5-HTHdh expressing neurosecretory cells were distributed in the cortex of the pleuropedal ganglion. Our results suggest that 5-HTHdh synthesized in the neural ganglia may be involved in oocyte maturation and spawning of H. discus hannai.

The Traditional Medicine Banhasasim-Tang Depolarizes Pacemaker Potentials of Cultured Interstitial Cells of Cajal through M3 Muscarinic and 5-HT3 Receptors in Murine Small Intestine.

BACKGROUND: Banhasasim-tang (BHSST) is a classic herbal formulation in traditional Chinese medicine widely used for gastrointestinal (GI) tract motility disorder. We investigated the effects of BHSST on the pacemaker potentials of cultured interstitial cells of Cajal (ICCs) in small intestine in vitro and its effects on GI motor functions in vivo. METHODS: We isolated ICCs from the small intestines and recorded pacemaker potentials in cultured ICCs with the whole-cell patch-clamp configuration in vitro. Intestinal transit rates (ITR%) were investigated in normal mice and GI motility dysfunction (GMD) mouse models in vivo. RESULTS: BHSST (20-50 mg/mL) depolarized pacemaker potentials and decreased their amplitudes in a concentration-dependent manner. Pretreatment with methoctramine (a muscarinic M2 receptor antagonist) did not inhibit BHSST-induced pacemaker potential depolarization. However, when we applied 1,1-dimethyl-4-diphenylacetoxypiperidinium iodide (4-DAMP; a muscarinic M3 receptor antagonist), BHSST-induced effects were blocked. Pretreatment with Y25130 (a 5-HT3 receptor antagonist) blocked BHSST-induced effects in ICCs. In addition, when we applied 4-DAMP and Y25130 together, BHSST-induced effects were completely blocked. Pretreatment with Ca2+-free solution or thapsigargin inhibited BHSST-induced effects. Moreover, BHSST blocked both the transient receptor potential melastatin (TRPM) 7 and voltage-sensitive calcium-activated chloride (anoctamin-1, ANO1) channels. In normal mice, ITR% values were significantly increased by BHSST in a dose-dependent manner. The ITR% of GMD mice was significantly reduced relative to those of normal mice, which were significantly reversed by BHSST in a dose-dependent manner. CONCLUSION: These results suggested that BHSST depolarizes the pacemaker potentials of ICCs in a dose-dependent manner through the M3 and 5-HT3 receptors via internal and external Ca2+-dependent and TRPM7- and ANO1-independent pathways in vitro. Moreover, BHSST increased ITR% in vivo in normal mice and GMD mouse models. Taken together, the results of this study showed that BHSST had the potential for development as a prokinetic agent in GI motility function.

Creation of the 5-hydroxytryptamine receptor 7 knockout rat as a tool for cardiovascular research.

Using CRISPR-Cas9 technology, we created a 5-HT7 receptor global knockout (KO) rat, on a Sprague-Dawley background, for use in cardiovascular physiology studies focused on blood pressure regulation. A stable line carrying indels in exons 1 and 2 of the rat Htr7 locus was established and validated. Surprisingly, 5-HT7 receptor mRNA was still present in the KO rat. However, extensive cDNA and genomic sequencing of KO tissues confirmed an 11 bp deletion in exon 1 and 4 bp deletion in exon 2. The exon 1 deletion resulted in a frameshifted mRNA sequence coding for a nonfunctional protein. While the Htr1B locus was a potential off-target for the guide RNAs designed for exon 2 of Htr7, there were no off-target sequence changes at this locus in the originating founder. When the F2 generation of KO was compared with wild-type (WT) counterparts, neither the male nor female KO rats were different in body size, fat weights, or mass of organs (kidney, heart, and brain) important to blood pressure. Females were smaller in mass than their counterpart males. Clinical measures of plasma from nonfasted rats revealed largely similar values, comparing WT and KO, of glucose, blood urea nitrogen, creatinine, phosphate, calcium, and albumin to name a few. Loss of a functional 5-HT7 receptor was validated by the complete loss of relaxation to the 5-HT1/7 receptor agonist 5-carboxamidotryptamine in the isolated abdominal vena cava. This newly created 5-HT7 receptor KO rat will be of use to investigate the importance of the 5-HT7 receptor in blood pressure regulation.

5-HT does not lower blood pressure in the 5-HT7 knockout rat.

The fall in mean arterial pressure (MAP) after 24 h of 5-HT infusion is associated with a dilation of the portal vein (PV) and abdominal inferior vena cava (Ab IVC); all events were blocked by the selective 5-HT7 receptor antagonist SB269970. Few studies have investigated the contribution of the 5-HT7 receptor in long-term cardiovascular control, and this requires an understanding of the chronic activation of the receptor. Using the newly created 5-HT7 receptor knockout (KO) rat, we presently test the hypothesis that continuous activation of the 5-HT7 receptor by 5-HT is necessary for the chronic (1 wk) depressor response and splanchnic venodilation. We also address if the 5-HT7 receptor contributes to endogenous cardiovascular regulation. Conscious MAP (radiotelemeter), splanchnic vessel diameter (ultrasound), and cardiac function (echocardiogram) were measured in ambulatory rats during multiday 5-HT infusion (25 µg·kg-1·min-1 via minipump) and after pump removal. 5-HT infusion reduced MAP and caused splanchnic venodilation of wild-type (WT) but not KO rats at any time point. The efficacy of 5-HT-induced contraction was elevated in the isolated abdominal inferior vena cava from the KO compared with WT rats, supporting loss of a relaxant receptor. Similarly, the efficacy of 5-HT causing an acute pressor response to higher doses of 5-HT in vivo was also increased in the KO vs. WT rat. Our work supports a novel mechanism for the cardiovascular effects of 5-HT, activation of 5-HT7 receptors mediating venodilation in the splanchnic circulation, which could prove useful in the treatment of cardiovascular disease.

Dopamine-induced functional activation of Gαq mediated by dopamine D1-like receptor in rat cerebral cortical membranes.

Although multiple roles of dopamine through D1-like (D1 and D5) and D2-like (D2, D3, and D4) receptors are initiated primarily through stimulation or inhibition of adenylyl cyclase via Gs/olf or Gi/o, respectively, there have been many reports indicating diverse signaling mechanisms that involve alternative G protein coupling. In this study, dopamine-induced Gαq activation in rat brain membranes was investigated. Agonist-induced Gαq activation was assessed by increase in guanosine-5'-O-(3-[35S]thio)triphosphate ([35S]GTPγS) binding to Gαq determined by [35S]GTPγS binding/immunoprecipitation assay in rat brain membranes. Dopamine-stimulated Gαq functionality was highest in cortex as compared to hippocampus or striatum. In cerebral cortical membranes, this effect was mimicked by benzazepine derivatives with agonist properties at dopamine D1-like receptors, that is, SKF83959, SKF83822, R(+)-SKF81297, R(+)-SKF38393, and SKF82958, but not by the compounds with dopamine D2-like receptor agonist properties except for aripiprazole. Against expectation, stimulatory effects were also induced by SKF83566, R(+)-SCH23390, and pergolide. The pharmacological profiling by using a series of antagonists indicated that dopamine-induced response was mediated through dopamine D1-like receptor, which was distinct from the receptor involved in 5-HT-induced response (5-HT2A receptor). Conversely, the responses induced by SKF83566, R(+)-SCH23390, and pergolide were most likely mediated by 5-HT2A receptor, but not by dopamine D1-like receptor. Caution should be paid when interpreting the experimental data, especially in behavioral pharmacological research, in which SKF83566 or R(+)-SCH23390 is used as a standard selective dopamine D1-like receptor antagonist. Also, possible clinical implications of the agonistic effects of pergolide on 5-HT2A receptor has been mentioned.

Cost-Effectiveness of Reclassifying Triptans in Australia: Application of an Economic Evaluation Approach to Regulatory Decisions.

BACKGROUND: Migraine is a common, chronic, disabling headache disorder. Triptans, used as an acute treatment for migraine, are available via prescription in Australia. An Australian Therapeutic Goods Administration (TGA) committee rejected reclassifying sumatriptan and zolmitriptan from prescription medicine to pharmacist-only between 2005 and 2009, largely on the basis of concerns about patient risk. Nevertheless, pharmacist-only triptans may reduce migraine duration and free up healthcare resources. OBJECTIVES: To estimate the cost-effectiveness of reclassifying triptans from prescription-only to pharmacist-only in Australia. METHODS: The study design included decision-analytic modeling combining data from various sources. Behavior before and after reclassification was estimated using medical practitioner and patient surveys and also administrative data. Health outcomes included migraine frequency and duration as well as adverse events (AEs) discussed by the TGA committee. Efficacy and AEs were estimated using randomized controlled trials and observational studies. RESULTS: Reclassifying triptans will reduce migraine duration but increase AEs. This will result in 337 quality-adjusted life-years gained at an increased cost of A$5.9 million over 10 years for all Australian adults older than 15 years (19.6 million). The incremental cost-effectiveness ratio was estimated to be A$17 412/quality-adjusted life-year gained. CONCLUSIONS: The incremental cost-effectiveness ratio is likely to be considered cost-effective by Australian decision makers. Serotonin syndrome, a key concern of the TGA committee, had little impact on the results. Further research is needed regarding pharmacist-only triptan use by migraineurs currently using over-the-counter medicines and by nonmigraineurs, the efficacy of triptans, and the risk of cardiovascular and cerebrovascular AEs and chronic headaches with triptans.

Structural insight into the serotonin (5-HT) receptor family by molecular docking, molecular dynamics simulation and systems pharmacology analysis.

Serotonin (5-HT) receptors are proteins involved in various neurological and biological processes, such as aggression, anxiety, appetite, cognition, learning, memory, mood, sleep, and thermoregulation. They are commonly associated with drug abuse and addiction due to their importance as targets for various pharmaceutical and recreational drugs. However, due to a high sequence similarity/identity among 5-HT receptors and the unavailability of the 3D structure of the different 5-HT receptor, no report was available so far regarding the systematical comparison of the key and selective residues involved in the binding pocket, making it difficult to design subtype-selective serotonergic drugs. In this work, we first built and validated three-dimensional models for all 5-HT receptors based on the existing crystal structures of 5-HT1B, 5-HT2B, and 5-HT2C. Then, we performed molecular docking studies between 5-HT receptors agonists/inhibitors and our 3D models. The results from docking were consistent with the known binding affinities of each model. Sequentially, we compared the binding pose and selective residues among 5-HT receptors. Our results showed that the affinity variation could be potentially attributed to the selective residues located in the binding pockets. Moreover, we performed MD simulations for 12 5-HT receptors complexed with ligands; the results were consistent with our docking results and the reported data. Finally, we carried out off-target prediction and blood-brain barrier (BBB) prediction for Captagon using our established hallucinogen-related chemogenomics knowledgebase and in-house computational tools, with the hope to provide more information regarding the use of Captagon. We showed that 5-HT2C, 5-HT5A, and 5-HT7 were the most promising targets for Captagon before metabolism. Overall, our findings can provide insights into future drug discovery and design of medications with high specificity to the individual 5-HT receptor to decrease the risk of addiction and prevent drug abuse.

Fluoxetine oral treatment discloses 5-HT1D receptor as vagoinhibitor of the cardiac cholinergic neurotransmission in rat.

Although depression and cardiovascular diseases are related, the role of antidepressants such as fluoxetine (increasing serotonin levels) within cardiac regulation remains unclear. We aimed to determine whether fluoxetine modifies the pharmacological profile of serotonergic influence on vagal cardiac outflow. Rats were treated with fluoxetine (10 mg/kg per day; p.o.) for 14 days or equivalent volumes of drinking water (control group); then, they were pithed and prepared for vagal stimulation. Bradycardic responses were obtained by electrical stimulation of the vagal fibers (3, 6, and 9 Hz) or i.v. acetylcholine (ACh; 1, 5, and 10 µg/kg). The i.v. administration of 5-hydroxytryptamine (5-HT; 10 and 50 µg/kg) inhibited the vagally induced bradycardia. 5-CT (5-HT1/7 agonist) and L-694,247 (5-HT1D agonist) mimicked the serotonin inhibitory effect while α-methyl-5-HT (5-HT2 agonist) was devoid of any action. SB269970 (5-HT7 antagonist) did not abolish 5-CT inhibitory action on the electrically induced bradycardia. Pretreatment with LY310762 (5-HT1D antagonist) blocked the effects induced by L-694,247 and 5-CT. 5-HT and 5-CT failed to modify the bradycardia induced by exogenous ACh. Our outcomes suggest that fluoxetine treatment modifies 5-HT modulation on heart parasympathetic neurotransmission in rats, evoking inhibition of the bradycardia via prejunctional 5-HT1D in pithed rats.

Molecular characterization, expression analysis, and functional properties of multiple 5-hydroxytryptamine receptors in Pacific abalone (Haliotis discus hannai).

Neurotransmitters such as serotonin (5-hydroxytryptamine; 5-HT) in the central nervous system regulate diverse physiological functions, including reproduction, feeding, learning, and memory, in diverse animal phyla. 5-HT and the 5-HT1 subtype receptor play important roles in sexual maturation and in the initiation of gamete release in mollusks. However, little is known about the involvement of other 5-HT receptor subfamilies in the reproduction process. In the present study, we identified the cDNAs encoding eight subtypes of 5-HT receptors from the ganglia tissues of the Pacific abalone Haliotis discus hannai (Mollusca; Gastropoda; Haliotidae), and examined the gonadal expression of the transcripts of 5-HT receptors. A phylogenetic analysis indicated that the molluskan 5-HT receptors are largely classified into four major clades: 5-HT1/5/7, 5-HT2, 5-HT4, and 5-HT6. Among the H. discus hannai (Hdh) 5-HT1-7 transcripts, Hdh5-HT1B, 4A, 4B, and 6 were the major subtypes detected in the mature ovary. Estradiol-17ß injection into the pedal sinus induced the downregulation of 5-HT4B and upregulation of 5-HT6 transcripts in the ovary of mature abalone within 72 h. In HEK293 cells overexpressing Hdh5-HT1B, forskolin-stimulated cAMP response element luciferase (CRE-Luc) reporter activity was inhibited by 5-HT in a dose-dependent manner, whereas serum response element luciferase (SRE-Luc) activity was not affected. In Hdh5-HT4A-expressing HEK293 cells, forskolin-stimulated CRE-Luc and SRE-Luc reporter activities were both marginally increased by treatment with a high dose of 5-HT. Our results provide new insights into the roles of 5-HT through diverse G protein-coupled 5-HT receptors in the reproductive process of mollusks.

Regional distribution of serotonergic receptors: a systems neuroscience perspective on the downstream effects of the multimodal-acting antidepressant vortioxetine on excitatory and inhibitory neurotransmission.

Previous work from this laboratory hypothesized that the multimodal antidepressant vortioxetine enhances cognitive function through a complex mechanism, using serotonergic (5-hydroxytryptamine, 5-HT) receptor actions to modulate gamma-butyric acid (GABA) and glutamate neurotransmission in key brain regions like the prefrontal cortex (PFC) and hippocampus. However, serotonergic receptors have circumscribed expression patterns, and therefore vortioxetine's effects on GABA and glutamate neurotransmission will probably be regionally selective. In this article, we attempt to develop a conceptual framework in which the effects of 5-HT, selective serotonin reuptake inhibitors (SSRIs), and vortioxetine on GABA and glutamate neurotransmission can be understood in the PFC and striatum-2 regions with roles in cognition and substantially different 5-HT receptor expression patterns. Thus, we review the anatomy of the neuronal microcircuitry in the PFC and striatum, anatomical data on 5-HT receptor expression within these microcircuits, and electrophysiological evidence on the effects of 5-HT on the behavior of each cell type. This analysis suggests that 5-HT and SSRIs will have markedly different effects within the PFC, where they will induce mixed effects on GABA and glutamate neurotransmission, compared to the striatum, where they will enhance GABAergic interneuron activity and drive down the activity of medium spiny neurons. Vortioxetine is expected to reduce GABAergic interneuron activity in the PFC and concomitantly increase cortical pyramidal neuron firing. However in the striatum, vortioxetine is expected to increase activity at GABAergic interneurons and have mixed excitatory and inhibitory effects in medium spiny neurons. Thus the conceptual framework developed here suggests that vortioxetine will have regionally selective effects on GABA and glutamate neurotransmission.

Involvement of PPARγ in the protective action of tropisetron in an experimental model of ulcerative colitis.

Inflammatory bowel disease (IBD) is a chronic inflammation of the gastrointestinal (GI) tract. Tropisetron, a selective 5-HT3 receptor antagonist, is highly used to counteract chemotherapy-induced emesis. Previous studies revealed the anti-inflammatory properties of this drug. The aim of this study was to evaluate the role of peroxisome proliferator-activated receptor gamma (PPARγ) receptor in the protective effect of tropisetron in an animal model of ulcerative colitis. Experimental colitis was induced by a single intra-colonic instillation of 4% (V/V) acetic acid in male rats. Tropisetron (3 mg/kg) and GW9662 (PPARγ antagonist) (5 mg/kg) were given twice daily for 2 days after colitis induction. Forty-eight hours after induction of colitis, colon was removed and macroscopic and microscopic features were given. Moreover, colonic concentrations of malondialdehyde (MDA), nitric oxide (NO), tumor necrosis factor-α (TNF-α), interleukin-1ß (IL-1ß) levels, myeloperoxidase (MPO), and PPARγ activity were assessed. Both macroscopic and histopathological features of colonic injury were markedly ameliorated by tropisetron. Likewise, levels of NO, MDA, TNF-α, and IL-1ß diminished significantly (p < .05). GW9662 reversed the effect of tropisetron on these markers partially or completely. In addition, tropisetron increased the PPARγ and decreased the MPO activity (p < .05). Tropisetron exerts notable anti-inflammatory effects in acetic acid-induced colitis in rats, which is probably mediated through PPARγ receptors.

Expression of messenger molecules and receptors in rat and human sphenopalatine ganglion indicating therapeutic targets.

BACKGROUND: Migraine and Cluster Headache (CH) are two primary headaches with severe disease burden. The disease expression and the mechanisms involved are poorly known. In some attacks of migraine and in most attacks of CH, there is a release of vasoactive intestinal peptide (VIP) originating from parasympathetic cranial ganglia such as the sphenopalatine ganglion (SPG). Patients suffering from these diseases are often deprived of effective drugs. The aim of the study was to examine the localization of the botulinum toxin receptor element synaptic vesicle glycoprotein 2A (SV-2A) and the vesicular docking protein synaptosomal-associated protein 25 (SNAP25) in human and rat SPG. Additionally the expression of the neurotransmitters pituitary adenylate cyclase activating polypeptide (PACAP-38), nitric oxide synthase (nNOS), VIP and 5-hydroxttryptamine subtype receptors (5-HT1B,1D,1F) were examined. METHODS: SPG from adult male rats and from humans, the later removed at autopsy, were prepared for immunohistochemistry using specific antibodies against neurotransmitters, 5-HT1B,1D,1F receptors, and botulinum toxin receptor elements. RESULTS: We found that the selected neurotransmitters and 5-HT receptors were expressed in rat and human SPG. In addition, we found SV2-A and SNAP25 expression in both rat and human SPG. We report that all three 5-HT receptors studied occur in neurons and satellite glial cells (SGCs) of the SPG. 5-HT1B receptors were in addition found in the walls of intraganglionic blood vessels. CONCLUSIONS: Recent focus on the SPG has emphasized the role of parasympathetic mechanisms in the pathophysiology of mainly CH. The development of next generation's drugs and treatment of cranial parasympathetic symptoms, mediated through the SPG, can be modulated by treatment with BoNT-A and 5-HT receptor agonists.