Effects of 5-hydroxytryptophan on morphine-induced sensitization in mice

To investigate the involvement of central serotonergic system in behavioral sensitization to morphine in mice. Male Kunming mice were treated （i.p.） with saline or morphine 10 mg/kg twice daily for 3 d and then drug manipulation was suspended for 5 d. On day 9, a challenge dose of morphine （10 mg/kg） was given and the locomotor activity was measured for 60 rain to confkrm the establishment of behavioral sensitization in mice. Moreover, 5-hydroxytryptophan （5-HTP）, a precursor of serotonin, at the doses of 20-80 mg/kg was given i.p. in combination with daily morphine treatment （induction）, during the morphine treatment suspension （transfer） or prior to the challenge dose of morphine （expression） and locomotor activity was measured on day 9 after the challenge dose of morphine. Twice daily of morphine injection induced robust behavioral sensitization in mice as evidenced by significantly higher locomotion on day 9 for multiple treatment with morphine than saline in mice. 5-HTP treatment selec- tively and dose-dependently blocked the induction, but not the transfer nor the expression of morphine induced behavioral sensitization. This study provides clear evidence that up-regulation of central serotonergic system may suppress the induction of morphine sensitization in mice.

Comparison of 5-hydroxytryptophan signaling pathway characteristics in diarrhea-predominant irritable bowel syndrome and ulcerative colitis

AIM: To study differences in the visceral sensitivity of the colonic mucosa between patients with diarrheapredominant irritable bowel syndrome(IBS-D) and those with ulcerative colitis(UC) in remission and to relate these differences with changes in the 5-hydroxytryptophan(5-HT) signaling pathway. METHODS: Gastrointestinal symptoms were used to determine the clinical symptom scores and rectal visceral sensitivity of patients with IBS-D and patients with UC in remission. Blood levels of 5-HT and5-hydroxyindoleacetic acid(5-HIAA) were measured using an HPLC-electrochemical detection system. The levels of 5-HT 3 receptor(3R), 4R, and 7R m RNAs in colonic biopsy samples were detected using reverse transcription-polymerase chain reaction. The protein expression of TPH1 was analyzed by Western blot and immunohistochemistry.RESULTS: Abdominal pain or discomfort, stool frequency, and the scores of these symptoms in combination with gastrointestinal symptoms were higher in the IBS-D and UC groups than in the control groups. However, no significant differences were observed between the IBS-D and UC remission groups. With respect to rectal visceral sensitivity, the UC remission and IBS-D groups showed a decrease in the initial perception threshold, defecating threshold and pain threshold. However, these groups exhibited significantly increased anorectal relaxation pressure. Tests examining the main indicators of the 5-HT signaling pathway showed that the plasma 5-HT levels, 5-HIAA concentrations, TPH1 expression in the colonic mucosa, and 5-HT3 R and 5-HT5 R expression were increased in both the IBS-D and the UC remission groups; no increases were observed with respect to 5-HT7 R expression.CONCLUSION: The IBS-D and UC groups showed similar clinical symptom scores, visceral sensitivity, and levels of serotonin signaling pathway indicators in the plasma and colonic mucosa. However, the pain threshold and 5-HT7 R expression in the colonic mucosa were significantly different between these groups. The results reveal that(1) IBS-D and UC are related to visceral sensitivity pathogenesis and the clinical manifestations of these conditions and(2) the observed differences in visceral hypersensitivity are possibly due to differences in levels of the 5-HT7 receptor, a component of the 5-HT signaling pathway.

Morinda officinalis oligosaccharides increase serotonin in the brain and ameliorate depression via promoting 5-hydroxytryptophan production in the gut microbiota

Morinda officinalis oligosaccharides(MOO) are an oral drug approved in China for the treatment of depression in China. However, MOO is hardly absorbed so that their anti-depressant mechanism has not been elucidated. Here, we show that oral MOO acted on tryptophan → 5-hydroxytryptophan(5-HTP) → serotonin(5-HT) metabolic pathway in the gut microbiota. MOO could increase tryptophan hydroxylase levels in the gut microbiota which accelerated 5-HTP production from tryptophan;meanwhile, MOO inhibited 5-hydroxytryptophan decarboxylase activity, thus reduced 5-HT generation,and accumulated 5-HTP. The raised 5-HTP from the gut microbiota was absorbed to the blood, and then passed across the blood-brain barrier to improve 5-HT levels in the brain. Additionally, pentasaccharide,as one of the main components in MOO, exerted the significant anti-depressant effect through a mechanism identical to that of MOO. This study reveals for the first time that MOO can alleviate depression via increasing 5-HTP in the gut microbiota.

Analgesis and Wound Healing Effect of Chitosan and Carboxymethyl Chitosan on Scalded Rats

Analgesis and wound healing effect of chitosan and carboxymethyl chitosan on scalded rats were investigated. A II degree scald model was established in rats, which was subsequently treated with chitosan and carboxymethyl chitosan solution, respectively. The concentration of bradykinin and 5-hydroxytryptophan was detected by assaying enzyme-linked immunosorbent. Healing condition was observed and pathological sections were made to determine the healing effect of chitosan and carboxymethyl chitosan. Results showed that the concentration of bradykinin and 5-hydroxytryptophan peaked at the third hour post-wound in all groups, while the concentration of hydroxyproline peaked at the seventh day post-wound in both chitosan and carboxymethyl chitosan group. The concentration of bradykinin and 5-hydroxytryptophan of carboxymethyl chitosan group was significantly lower than that of control(P < 0.05), while that of chitosan group was similar to that of control(P > 0.05). These findings indicated that carboxymethyl chitosan reduced the concentration of algogenic substances, resulting in analgesia. During the whole recovery process, the hydroxyproline concentration in chitosan and carboxymethyl chitosan group on day 3 and 7 was significantly higher than that of control(P < 0.01); however the significance of such a highness decreased on day 14(P < 0.05). These findings indicated that chitosan and carboxymethyl chitosan accelerated tissue repair. Meanwhile, chitosan performed better in healing than carboxymethyl chitosan in both decrustation and healing time. In conclusion, carboxymethyl chitosan showed significant analgesis and wound-healing promotion effect, but chitosan only showed wound-healing promotion effect.

Evaluation of necrosis avidity of radioiodinated 5-hydroxytryptophan and its potential applications in myocardial infarction imaging

This study aimed to seek necrosis avid agents with high safety from DNA binding agents. The interaction of 5-hydroxytryptophan(5-HTP) with DNA was investigated by a series of spectroscopic studies. Then, 5-HTP was labeled with iodine-131([^(131)I]5-HTP) and the necrosis avidity of [^(131)I]5-HTP was evaluated by in vitro cell binding assays, in vivo biodistribution experiments and blocking experiment. Finally, the potential of [^(131)I]5-HTP to image necrotic myocardium was explored in rat models with myocardial infarction by SPECT/CT imaging. Results showed that 5-HTP bound to DNA in groove binding mode and the binding constant was 1.69×10~4 L/mol. [~(^(131))I]5-HTP showed specific affinity to necrotic A549 cells,which might be related to cell nucleus. Biodistribution and autoradiography results showed preferential accumulation of [^(131)I]5-HTP in necrotic muscle(necrotic/viable muscle ratio: 6.95 ? 0.68 at 3 h postinjection(p.i.)), which could be blocked by 5-HTP with 66.7% decline, indicating that [^(131)I]5-HTP might share the same necrotic targets with 5-HTP. On SPECT/CT images, a hotspot was clearly observed at 3h p.i.in the necrotic myocardium while not in the control myocardium. In conclusion, [^(131) I]5-HTP is a novel necrosis avid agent and can rapidly visualize necrotic myocardium at 3 h p.i. The necrosis avidity mechanism of [^(131) I]5-HTP may be attributed to its interactions with exposed DNA in the necrotic tissues.

Two-step production of monoamines in monoenzymatic cells in the spinal cord:a different control strategy of neurotransmitter supply?

Monoamine neurotransmitters play an important role in the modulation of sensory, motor and autonomic functions in the spinal cord. Although traditionally it is believed that in mammalian spinal cord, monoamine neurotransmitters mainly originate from the brain, accumulating evidence indicates that especially when the spinal cord is injured, they can also be produced in the spinal cord. In this review, I will present evidence for a possible pathway for two-step synthesis of dopamine and serotonin in the spinal cord. Published data from different sources and unpublished data from my own ongoing projects indicate that monoenzymatic cells expressing aromatic L-amino acid decarboxylase（AADC）, tyrosine hydroxylase（TH） or tryptophan hydroxylase（TPH） are present in the spinal cord and that these TH and THP cells often lie in close proximity to AADC cells. Prompted by the above evidence, I hypothesize that dopamine and serotonin could be synthesized sequentially in two monoenzymatic cells in the spinal cord via a TH-AADC and a TPH-AADC cascade respectively. The monoamines synthesized through this pathway may compensate for lost neurotransmitters following spinal cord injury and also may play specific roles in the recovery of sensory, motor and autonomic functions.

Antidepressant-like effects of the ethanolic extract of XiaobuxinTang,a traditional Chinese herbal prescription in animal models of depression

Background Xiaobuxin-Tang, a traditional Chinese herbal prescription recorded in a silk scroll unearthed from Mogao Caves of Dunhuang has been indicated that it can remit depressive disorder. The present study was designed to investigate its antidepressant effects in various animal depression models.Methods Xiaobuxin-Tang was extracted by 70% alcohol, and then three behavioral despair models and 5-Hydroxytryptophan （HTP）-induced head twitch response model were adopted to assess the antidepressant effects of the ethanolic extract of Xiaobuxin-Tang with the study on spontaneous motor activity. Groups of mice and rats received oral treatment with Xiaobuxin-Tang （150-1200 mg/kg） only once acutely in all tests. The duration of immobility was measured during the last 4 minutes of the 6-minutes test period in mice forced swimming test, rats forced swimming test and mice tail suspension test. In 5-HTP-induced head twitch response, the mice were intraperitoneally administered with 120 mg/kg of L-5-HTP, and then the cumulative number of head twitches was counted in 20 minutes. Spontaneous motor activities of mice were recorded automatically in 10 minutes by VIDEOMEX-V image analytic system.Results The extract at doses of 300 mg/kg （p.o.） and 600 mg/kg （p.o.） significantly decreased the duration of immobility time in a dose dependent manner in mice forced swimming test; also, the extract at dose of 1200 mg/kg （p.o.） significantly decreased the duration of immobility time in rat forced swimming test. Furthermore, the extract at a dose of 600 mg/kg had the same effect in mice tail suspension test. Meanwhile, the extract at the effective doses for behavioral despair models, had no effect on spontaneous motor activity in mice. The extract （300-1200 mg/kg, p.o.） also increased the accumulative number of the 5-HTP-induced head twitch response in mice in 20 minutes.Conclusion Our results suggested that the ethanolic extract of Xiaobuxin-Tang exerts antidepressant-like effect.