A number of studies have demonstrated that 5-hydroxytryptamine (5-HT) can induce muscle contraction or relaxation response and enhance secretion in the gastrointestinal tract via a multiplicity of 5-HT receptor subtypes. In the present study, we investigated the pharmacological characterization of the 5-HT-induced contractile response in longitudinal smooth muscle isolated from the feline ileum. Addition of 5-HT into muscle chambers enhanced the basal tone and spontaneous activity in a concentration-dependent manner. The neurotoxin tetrodotoxin did not alter the 5-HT-induced contraction of the longitudinal muscles. Neither atropine nor guanethidine affected the contraction. The 5-HT agonists, 5-methylserotonin hydrochloride and mosapride, also evoked concentration-dependent contractions. The 5-HT-induced contraction was enhanced by the 5HT2 receptor antagonist ketanserin and the 5-HT3 receptor antagonist ondansetron but was inhibited by the 5-HT1 receptor antagonist methysergide and 5-HT4 receptor antagonist GR113808. These results indicate that 5-HT1 and 5-HT4 receptors may mediate the contraction of the 5-HT-induced response and 5-HT2 and 5-HT3 receptors may mediate 5-HT-induced relaxation in feline ileal longitudinal smooth muscles.
Atropine ; Benzamides ; Contracts ; Gastrointestinal Tract ; Guanethidine ; Ileum ; Indoles ; Ketanserin ; Methysergide ; Morpholines ; Muscle Contraction ; Muscle, Smooth ; Muscles ; Ondansetron ; Receptors, Serotonin ; Receptors, Serotonin, 5-HT1 ; Receptors, Serotonin, 5-HT3 ; Receptors, Serotonin, 5-HT4 ; Relaxation ; Serotonin ; Serotonin Receptor Agonists ; Sulfonamides ; Tetrodotoxin

BACKGROUND AND OBJECTIVES: This study was aimed to explore the effects of the 5-hydroxytryptamine (5-HT) on potassium currents in rat vestibular nuclear neurons. MATERIALS AND METHOD: Sprague-Dawley rats aged 14 to 16 days were anesthetized with ether and decapitated. After enzymatic digestion, the portion of medial vestibular nucleus neuron was removed by micropunching and gently agitated. The dissociated neurons were transferred into a recording chamber mounted on an inverted microscope and whole-cell membrane currents were recorded at room temperature by using standard patch-clamp techniques. RESULTS: When cells were held at -70 mV and depolarized from -60 mV to +40 mV in 10 mV increments, sustained outward potassium currents were evoked. The response of medial vestibular nuclear neurons to 5-HT was not uniform. The outward potassium currents were increased in 17 of 40 cells and decreased in 23 of 40 cells. 5-carboxamidotryptamine, 5-HT1 agonist increased the outward potassium currents of the medial vestibular nuclear cell. alpha-methyl-5-hydroxytryptamine, 5-HT2 agonist decreased the outward potassium currents of the medial vestibular nuclear cell. CONCLUSION: These results suggest that 5-HT affects the potassium currents of the cell with different effects according to the receptor subtype on which it acts.
Animals ; Digestion ; Dihydroergotamine ; Ether ; Membranes ; Neurons* ; Patch-Clamp Techniques ; Potassium Channels ; Potassium* ; Rats* ; Rats, Sprague-Dawley ; Serotonin 5-HT1 Receptor Agonists ; Serotonin 5-HT2 Receptor Agonists ; Serotonin* ; Vestibular Nuclei

Irritable bowel syndrome is a group of symptoms that includes abdominal pain and changes in the form and frequency of stool. Since its symptoms are usually long-lasting, the disease significantly degrades quality of life. Several pharmacological therapies have been suggested according to the type of symptoms (e.g., abdominal pain, constipation, or diarrhea). In order to control abdominal pain, smooth muscle antispasmodics, antidepressants including tricyclic antidepressants and selective serotonin reuptake inhibitors, or 5-HT3 antagonists can be used. To improve constipation, dietary fiber or laxatives, 5-HT4 agonists, and chloride channel activators are available. Opioid agonists, mixed opioid agonists/antagonists such as eluxadoline, and bile salt sequestrants can be considered for diarrhea. In addition, probiotics and non-absorbable oral antibiotics can be used for the normalization of the gut microbiome and the treatment of small intestinal bacterial overgrowth, respectively. It is necessary to understand the characteristics of each drug and their combinations, because any single regimen cannot improve all symptoms in patients with irritable bowel syndrome. In this review, the mechanisms of action, efficacy, and adverse events associated with drugs used for irritable bowel syndrome are summarized.
Abdominal Pain ; Anti-Bacterial Agents ; Antidepressive Agents ; Antidepressive Agents, Tricyclic ; Bile ; Chloride Channel Agonists ; Constipation ; Diarrhea ; Dietary Fiber ; Drug Therapy* ; Gastrointestinal Microbiome ; Humans ; Irritable Bowel Syndrome* ; Laxatives ; Muscle, Smooth ; Parasympatholytics ; Probiotics ; Quality of Life ; Serotonin 5-HT3 Receptor Antagonists ; Serotonin 5-HT4 Receptor Agonists ; Serotonin Uptake Inhibitors

Irritable bowel syndrome is a group of symptoms that includes abdominal pain and changes in the form and frequency of stool. Since its symptoms are usually long-lasting, the disease significantly degrades quality of life. Several pharmacological therapies have been suggested according to the type of symptoms (e.g., abdominal pain, constipation, or diarrhea). In order to control abdominal pain, smooth muscle antispasmodics, antidepressants including tricyclic antidepressants and selective serotonin reuptake inhibitors, or 5-HT3 antagonists can be used. To improve constipation, dietary fiber or laxatives, 5-HT4 agonists, and chloride channel activators are available. Opioid agonists, mixed opioid agonists/antagonists such as eluxadoline, and bile salt sequestrants can be considered for diarrhea. In addition, probiotics and non-absorbable oral antibiotics can be used for the normalization of the gut microbiome and the treatment of small intestinal bacterial overgrowth, respectively. It is necessary to understand the characteristics of each drug and their combinations, because any single regimen cannot improve all symptoms in patients with irritable bowel syndrome. In this review, the mechanisms of action, efficacy, and adverse events associated with drugs used for irritable bowel syndrome are summarized.
Abdominal Pain ; Anti-Bacterial Agents ; Antidepressive Agents ; Antidepressive Agents, Tricyclic ; Bile ; Chloride Channel Agonists ; Constipation ; Diarrhea ; Dietary Fiber ; Drug Therapy* ; Gastrointestinal Microbiome ; Humans ; Irritable Bowel Syndrome* ; Laxatives ; Muscle, Smooth ; Parasympatholytics ; Probiotics ; Quality of Life ; Serotonin 5-HT3 Receptor Antagonists ; Serotonin 5-HT4 Receptor Agonists ; Serotonin Uptake Inhibitors

A significant proportion of chronic constipation patients are dissatisfied with their treatment. Recently, a number of new medications have been introduced for patients refractory to conventional laxatives, such as prucalopride, lubiprostone, linaclotide, and elobixibat. Prucalopride is a novel gastrointestinal prokinetic agent that acts as a 5-hydroxytryptamine type 4 (5-HT4) agonist. Compared with older nonselective 5-HT4 agonists, the higher selectivity of prucalopride for 5-HT4 receptors can reduce the risk of significant adverse cardiovascular events. Prucalopride improves stool frequency and consistency, and reduces the need for rescue medications. Lubiprostone, a chloride channel activator, increases the secretion of intestinal fluid, improves the stool frequency and consistency, and reduces straining. Linaclotide, a guanylate cyclase-C agonist, is effective in treating patients with chronic constipation and its effect on visceral sensitivity, as shown mainly in animal studies, provides an attractive pharmaceutical option for patients with irritable bowel syndrome with constipation. Elobixibat is an ileal sodium-dependent bile acid transporter inhibitor that blocks the enterohepatic circulation of bile acids, increasing the bile acid concentration in the intestine, which accelerates colonic transit and softens the stool. A phase III trial of the treatment of chronic constipation and irritable bowel syndrome with constipation is underway. The clinical application of new-generation laxatives will contribute to the management of chronic constipation refractory to conventional laxatives.
Animals ; Bile ; Bile Acids and Salts ; Chloride Channels ; Colon ; Constipation ; Enterohepatic Circulation ; Humans ; Intestines ; Irritable Bowel Syndrome ; Laxatives* ; Receptors, Serotonin, 5-HT4 ; Serotonin ; Serotonin 5-HT4 Receptor Agonists ; Lubiprostone

BACKGROUND/AIMS: To compare the efficacy and safety of prucalopride, a novel selective high-affinity 5-hydroxytryptamine type 4 receptor agonist, versus placebo, in Asian and non-Asian women with chronic constipation (CC). METHODS: Data of patients with CC, receiving once-daily prucalopride 2-mg or placebo for 12-weeks, were pooled from 4 double-blind, randomized, phase-III trials (NCT00488137, NCT00483886, NCT00485940 and NCT01116206). The efficacy endpoints were: average of > or = 3 spontaneous complete bowel movements (SCBMs)/week; average increases of > or = 1 SCBMs/week; and change from baseline in each CC-associated symptom scores (bloating, abdominal pain, hard stool and straining). RESULTS: Overall, 1,596 women (Asian [26.6%], non-Asian [73.4%]) were included in this analysis. Significantly more patients in the prucalopride group versus placebo experienced an average of > or = 3 SCBMs/week in Asian (34% vs. 11%, P < 0.001) and non-Asian (24.6% vs. 10.6%, P < 0.001) subgroups. The number of patients reporting an increase of > or = 1 SCBMs/week from baseline was significantly higher in the prucalopride group versus placebo among both Asian (57.4% vs. 28.3%, P < 0.001) and non-Asian (45.3% vs. 24.0%, P < 0.001) subgroups. The difference between the subgroups was not statistically significant. Prucalopride significantly reduced the symptom scores for bloating, hard stool, and straining in both subgroups. CONCLUSIONS: Prucalopride 2-mg once-daily treatment over 12-weeks was more efficacious than placebo in promoting SCBMs and improvement of CC-associated symptoms in Asian and non-Asian women, and was found to be safe and well-tolerated. There were numeric differences between Asian and non-Asian patients on efficacy and treatment emergent adverse events, which may be partially due to the overlap with functional gastrointestinal disorders in non-Asian patients.
Abdominal Pain ; Asian Continental Ancestry Group* ; Constipation* ; Female ; Gastrointestinal Diseases ; Humans ; Serotonin ; Serotonin 5-HT4 Receptor Agonists

Functional nausea and vomiting is a broad term used to be described a subset of individuals who have chronic nausea and vomiting without apparent cause, despite extensive evaluation. According to the Rome III criteria, functional nausea and vomiting can be subdivided into three separate entities: chronic idiopathic nausea, functional vomiting and cyclic vomiting syndrome. Although no specific test can diagnose these diseases, the diagnostic approach requires excellent history taking combined with judicious diagnostic testing to exclude some organic cause of chronic nausea and vomiting. These conditions are probably not psychogenic in origin. Treatment remains empirical for all patients with functional nausea and vomiting. Reassurance and supportive physician-patient relationship, along with use of low-dose tricyclic antidepressants, can be beneficial in caring for patients with chronic idiopathic nausea and functional vomiting. The cornerstones of management for patients with cyclic vomiting syndrome are identifying and avoidance of triggering factors, treatment with prophylactic antimigraine agents, 5-HT3 antagonists, benzodiazepines and 5-HT1 agonists (sumatriptan), with supportive therapy.
Antidepressive Agents, Tricyclic ; Benzodiazepines ; Diagnostic Tests, Routine ; Humans ; Nausea ; Rome ; Serotonin 5-HT1 Receptor Agonists ; Serotonin 5-HT3 Receptor Antagonists ; Vomiting

AIMTo determine whether serotonin, a major neurotransmitter in brain, can modulate the production of secretory beta-amyloid protein precursor (sAPP) by activation of serotonin 5-HT2C receptor.

METHODSThe hippocampal slices of rats were incubated with various concentrations of serotonin, M-110, or L-107. sAPP released into the incubation medium were assayed by Western blot analysis assay with monoclonal antibody 22C11 for 2 h.

RESULTSVarious concentrations of serotonin (1.0 x 10(-2) - 1.0 x 10(3) micromol x L(-1)), M-110, a serotonin 5-HT2C agonist (1.5 x 10(-6) - 1.5 x 10(3) micromol x L(-1)), showed positive effect on the production of sAPP while L-107, a serotonin 5-HT2C antagonist (1.0 x 10(-9) - 1.0 x 10(3) micromol x L(-1)), showed negative effect on the production of sAPP over controls.

CONCLUSIONSerotonin modulates production of secretory amyloid beta-protein precursor through serotonin 5-HT2C receptor in incubated rat hippocampal slices.

Amyloid beta-Protein Precursor ; secretion ; Animals ; Hippocampus ; metabolism ; In Vitro Techniques ; Male ; Peptide Fragments ; secretion ; Rats ; Rats, Sprague-Dawley ; Receptor, Serotonin, 5-HT2C ; Serotonin ; pharmacology ; Serotonin 5-HT2 Receptor Agonists ; Serotonin 5-HT2 Receptor Antagonists

It has been known that central tryptaminergic system is closely related with the regulation of renal function, and that central 5-HT1 receptors mediate diuresis and natriuresis, whereas central 5-HT2 and 5-HT3 receptors mediate antidiuresis and antinatriuresis. Among many subtypes of 5-HT1 receptors, central 5-HT1A subtype has been suggested to exert diuretic and natriuretic effets. Further, it was recently observed that TFMPP, 5-HT1B agonist, elicited profound diuresis and natriuresis when administered intracerebroventricularly(icv). Present study is therefore undertaken to delineate the mechanism involved in the natriuresis and diuresis induced by icv TFMPP, employing the denervated and vagotomized rabbits. The influence of icv TFMPP on the plasma level of ANP was also observed. TFMPP 250 microgram/kg icv produced marked diuresis and natriuresis. Renal hemodynamics showed significant increase only in the first 10-min period after administration and thereafter tended to recover. However, natriuretic action lasted even after the increased renal hemodynamics returned to the control level, suggesting the decreased Na reabsorption in the tubules by humoral natriuretic factors. Systemic blood pressure transiently increased. In rabbits in which one kidney is denervated, with the contralateral intact as the control kidney, the denervated kidney also responded with natriuresis and diuresis like that of the normal rabbit. The contralateral kidney responded with typical diuretic and natriuretic effects, along with the marked increased of renal hemodynamics. The plasma ANP, one of humoral natriuretic factors, increased after administration of icv TFMPP, peaking at about 15min. In bilaterally vagotomized rabbits, the natriuretic and diuretic effects produced by icv TFMPP were greater than that of the normal rabbits. These observations suggest that the natriuresis and diuresis elicited by icv TFMPP result from the inhibition of tubular Na reabsorption mainly through mediation of ANP. It has been also suggested that vagus nerve might exert inhibitory influence on the diuretic action of icv TFMPP, because the renal effects was augmented in the vagotomized rabbits.
Atrial Natriuretic Factor ; Blood Pressure ; Diuresis ; Diuretics ; Hemodynamics ; Kidney ; Natriuresis ; Natriuretic Agents ; Negotiating ; Plasma ; Rabbits* ; Receptors, Serotonin, 5-HT1 ; Receptors, Serotonin, 5-HT3 ; Serotonin 5-HT1 Receptor Agonists ; Vagus Nerve

Irritable bowel syndrome (IBS) is one of the most prevalent functional gastrointestinal disorders. It is a multi-factorial disorder due to abnormal gastrointestinal motility, low-grade inflammation, visceral hypersensitivity, and communication between the gut-brain axis. IBS is traditionally treated with dietary and lifestyle modifications, fiber supplementation, and psychological and pharmacological therapies. Diet therapy including the low FODMAP diet and excluding certain food constituents is often used. Antispasmodics plus stool consistency modifiers to treat the major symptoms and defecation are first-line drug treatments. 5-Hydroxytryptamine (5-HT) receptors in the gastrointestinal tract, particularly 5-HT3 and 5-HT4 receptors are involved not only in modulating gut motility but in visceral sensory pathways. Drugs that act on both receptor classes appear to reduce visceral sensitivity and have inhibitory effects on motor activity in the distal intestine. 5-HT4 agonists may improve constipation-predominant IBS by normalizing bowel habits and thereby reduce abdominal pain. IBS continues to be a therapeutic challenge because of its diverse symptomatology and lack of a single pathophysiological target for drug intervention.
Abdominal Pain ; Axis, Cervical Vertebra ; Defecation ; Diet ; Diet Therapy ; Gastrointestinal Diseases ; Gastrointestinal Motility ; Gastrointestinal Tract ; Hypersensitivity ; Inflammation ; Intestines ; Irritable Bowel Syndrome* ; Korea ; Life Style ; Motor Activity ; Parasympatholytics ; Receptors, Serotonin, 5-HT4 ; Serotonin ; Serotonin 5-HT4 Receptor Agonists