Zingiber officinale Roscoe Rhizomes Attenuate Oxaliplatin-Induced Neuropathic Pain in Mice.

Oxaliplatin is a platinum derivative chemotherapeutic drug widely used against cancers, but even a single treatment can induce a severe allodynia that requires treatment interruption and dose diminution. The rhizome of Zingiber officinale roscoe (Z. officinale, ginger), has been widely used in traditional medicine to treat various diseases causing pain; however, its effect against oxaliplatin-induced neuropathic pain has never been assessed. In mice, a single oxaliplatin (6 mg/kg, i.p.) treatment induced significant cold and mechanical allodynia. Cold and mechanical allodynia were assessed by acetone drop and von Frey filament tests, respectively. Water extracts of Z. officinale (100, 300, and 500 mg/kg, p.o.) significantly attenuated both cold and mechanical allodynia induced by oxaliplatin. Intrathecal pre-treatment with the antagonist 5-HT1A (NAN-190, i.t., 1 µg), but not with the antagonist 5-HT2A (ketanserin, i.t., 1 µg), significantly blocked the analgesic effect of Z. officinale against both cold and mechanical allodynia. However, 5-HT3 antagonist (MDL-72222, i.t., 15 µg) administration only blocked the anti-allodynic effect of Z. officinale against cold allodynia. Real-time PCR analysis demonstrated that Z. officinale significantly increased the mRNA expression of the spinal 5-HT1A receptor that was downregulated after oxaliplatin injection. These results suggest that Z. officinale may be a viable treatment option for oxaliplatin-induced neuropathic pain.

Chronic BMY7378 treatment alters behavioral circadian rhythms.

The mammalian circadian clock is synchronized to the day : night cycle by light. Serotonin modulates the circadian effects of light, with agonists inhibiting response to light and antagonists enhancing responses to light. A special class of serotonergic compounds, the mixed 5-HT1A agonist/antagonists, potentiates light-induced phase advances by up to 400% when administered acutely. In this study, we examine the effects of one of these mixed 5-HT1A agonist/antagonists, BMY7378, when administered chronically. Thirty adult male hamsters were administered either vehicle or BMY7378 via surgically implanted osmotic mini pumps over a period of 28 days. In a light : dark cycle, chronic BMY7378 advanced the phase angle of entrainment, prolonged the duration of the active phase and attenuated the amplitude of the wheel-running rhythm during the early night. In constant darkness, chronic treatment with BMY7378 significantly attenuated light-induced phase advances, but had no significant effect on light-induced phase delays. Non-photic phase shifts to daytime administration of a 5-HT1A/7 agonist were also attenuated by chronic BMY7378 treatment. qRT-PCR analysis revealed that chronic BMY7378 treatment upregulated mRNA for 5-HT1A and 5-HT1B receptors in the hypothalamus and downregulated mRNA for 5-HT1A and monoamine oxidase-A in the brainstem. These results highlight adaptive changes of serotonin receptors in the brain to chronic treatment with BMY7378 and link such up- and downregulation to changes in important circadian parameters. Such long-term changes to the circadian system should be considered when patients are treated chronically with drugs that alter serotonergic function.

The effect of curcumin on the brain-gut axis in rat model of irritable bowel syndrome: involvement of 5-HT-dependent signaling.

Irritable bowel syndrome (IBS) is induced by dysfunction of central nervous and peripheral intestinal systems, which affects an estimated 10-15% population worldwide annually. Stress-related psychiatric disorders including depression and anxiety are often comorbid with gastrointestinal function disorder, such as IBS. However, the mechanism of IBS still remains unknown. Curcumin is a biologically active phytochemical presents in turmeric and has pharmacological actions that benefit patients with depression and anxiety. Our study found that IBS rats showed depression- and anxiety-like behaviors associated with decreased 5-HT (serotonin), BDNF (Brain-derived neurotrophic factor) and pCREB (phosphorylation of cAMP response element-binding protein) expression in the hippocampus after chronic acute combining stress (CAS). However, these decreased parameters were obviously increased in the colonic after CAS. Curcumin (40 mg/kg) reduced the immobility time of forced swimming and the number of buried marbles in behavioral tests of CAS rats. Curcumin also decreased the number of fecal output and abdominal withdrawal reflex (AWR) scores in response to graded distention. Moreover, curcumin increased serotonin, BDNF and pCREB levels in the hippocampus, but they were decreased in the colonic of CAS rats. 5-HT(1A) receptor antagonist NAN-190 reversed the effects of curcumin on behaviors and the changes of intestine, pCREB and BDNF expression, which are related to IBS. These results suggested that curcumin exerts the effects on IBS through regulating neurotransmitters, BDNF and CREB signaling both in the brain and peripheral intestinal system.

Altered expression of 5-HT1A receptors in adult rats induced by neonatal treatment with clomipramine.

Chronic administration of clomipramine (CMI) to neonatal rats produces behaviors that resemble a depressive state in adulthood. Dysfunctions in the activity of the central nervous system's serotonergic function are important in understanding the pathophysiology of depression. The serotonin system is implicated in major depression and suicide and is negatively regulated by somatodendritic 5-HT1A autoreceptors. Desensitization of 5-HT1A autoreceptors is implicated in the long latency of some antidepressant treatments. Alterations in 5-HT1A receptor levels are reported in depression and suicide. In this study, we analyzed the effect of neonatal administration of CMI on the activity of 5-HT1A receptors, both pre- and post-synaptically, by administering an agonist of 5-HT1A receptors, 8-OH-DPAT, and then subjecting the rats to the forced swimming test (FST) a common procedure used to detect signs of depression in rats. Also measured were levels of the mRNA expression of 5-HT1A receptors in the dorsal raphe (DR), the hypothalamus and the hippocampus. Wistar rats were injected twice daily with CMI at doses of 15mgkg(-1) or saline as vehicle (CON) via s.c. from postnatal day 8 for 14days. At 3-4months of age, one set of rats from each group (CON, CMI) was evaluated for the effect of a selective agonist to the 5-HT1A receptor subtype, 8-OH-DPAT, by testing in the FST. Also determined was the participation of the pre- or post-synaptic 5-HT1A receptor in the antidepressant-like action of 8-OH-DPAT. This involved administering an inhibitor of tryptophan hydroxylase, parachlorophenylalanine (PCPA), and pretreatment with 8-OH-DPAT before the FST test and to evaluate the rectal temperature and locomotor activity. The expression of the mRNA of the 5-HT1A receptors was examined in the dorsal raphe nucleus, the hypothalamus and the hippocampus using the semi-quantitative RT-PCR method. The results from this study corroborate that neonatal treatment with clomipramine induces a pronounced immobility in the FST when animals reach adulthood, manifested by a significant decrease in swimming behavior, though counts of climbing behavior were not modified. This effect was similar in magnitude when 8-OH-DPAT was administered to CON group. Furthermore, the administration of 8-OH-DPAT induces a significant and similar increase in rectal temperature and locomotor activity in both the CON as in the CMI group. Neonatal treatment with CMI resulted in a significant decrease in the expression of the mRNA of the 5-HT1A receptors in the DR (% more than vehicle) in adulthood. In the case of the postsynaptic receptors located in the hypothalamus and hippocampus, neonatal treatment with CMI induced a significant increase in the mRNA expression of the 5-HT1A receptors. These data suggest that neonatal treatment with CMI induces a downregulation of the mRNA of the 5-HT1A autoreceptors in the DR, and an increment in the expression of the postsynaptic 5-HT1A receptors. The results after the administration of PCPA and 8-OH-DPAT on FST, rectal temperature and locomotor activity for both groups suggest that the function of postsynaptic receptors remains unchanged. All together these data show that the depressive behavior observed in adulthood in this animal model may be associated with long-term alterations in the expression of the mRNA of the 5-HT1A receptors.

Partial agonistic effect of yokukansan on human recombinant serotonin 1A receptors expressed in the membranes of Chinese hamster ovary cells.

ETHNOPHARMACOLOGICAL RELEVANCE: Yokukansan (YKS) is a traditional Japanese medicine consisted of seven medicinal herbs and has been used for treatment of neurosis, insomnia, and behavioral and psychological symptoms of dementia (BPSD) in Japan. AIM OF THE STUDY: The aim of the present study is to clarify the intrinsic activity of YKS on serotonin (5-HT)1A and 5-HT2A receptors and also to determine the constituent herbs which are responsible for the effect of YKS. MATERIALS AND METHODS: The dry powdered extracts of YKS, seven constituent herbs, and YKS-analogues which were produced by eliminating one of the constituent herbs from YKS in the manufacturing process, were used for the evaluation. Competitive binding assays for 5-HT receptors and [(35)S]GTPgammaS binding assays for the evaluation of agonistic/antagonistic activity were performed using Chinese hamster ovary cell membranes stably expressing human recombinant 5-HT1A or 5-HT2A receptors. RESULTS: YKS (6.25-400 microg/ml) concentration-dependently inhibited the binding of [(3)H]8-OH-DPAT to 5-HT1A receptors. The IC(50) value was estimated to be 61.2 microg/ml. In contrast, YKS failed to inhibit the binding of [(3)H]ketanserin to 5-HT2A receptors. Only Uncaria hook (3.13-50 microg/ml), of the seven constituent herbal extracts, inhibited the [(3)H]8-OH-DPAT binding to 5-HT1A receptors in a concentration-dependent manner, and the IC(50) value was estimated to be 7.42 microg/ml. The extracts of YKS or Uncaria hook increased [(35)S]GTPgammaS binding to 5-HT1A receptors to approximately 50% of that of a full agonist, 5-HT. Both the competitive binding and [(35)S]GTPgammaS binding of YKS to 5-HT1A receptors were remarkably attenuated by eliminating Uncaria hook from YKS, but it was almost unchanged when one of the other constituent herbs was eliminated from YKS. CONCLUSION: These results suggest that YKS has a partial agonistic effect on 5-HT1A receptors, which is mainly attributed to Uncaria hook.

[Effect of long-term cold adaptation on the mRNA expression of serotonin 5-HT1A and 5-HT2A receptors].

The mRNA expression of serotonin receptors 5-HT1A and 5-HT2A was investigated by the quantitative method RT-PCR in rats adapted to cold (5 weeks at +4 -(+6) degrees C) and in control (5 weeks at +20-22 degrees C). Four brain regions were examined: frontal cortex, hypothalamus, hippocampus, and midbrain. The influence of cold adaptation on the mRNA expression of 5-HT15 receptor was not found to be absent. The mRNA expression of 5-HT2A receptor changed under long-term cold exposure. These changes in different brain regions were various: in hypothalamus, there was an increase of the 5-HT2A receptor mRNA expression; in the cortex, a decrease; in the hippocampus and midbrain, significant changes of the mRNA expression were absent. The findings appear bo te adaptive and, according to their localization in the central nervous system, regulatory. They also suggest involvement of brain serotoninergic system in mechanism of adaptive reorganization of temperature regulation.

[Quantitative assay of 5-HT(1A) serotonin receptor gene expression in the brain].

Serotonin 5-HT(1A) receptors participate in the regulation of many kinds of behavior and are implicated in the mechanism of action of anxiolitics and antidepressants. The investigation of 5-HT(1A) receptor gene expression is complicated by low concentration of the receptor mRNA. Our method of quantification of the receptor gene expression in brain structures includes estimation of the concentration of genomic DNA contamination, the number of cDNA copies of glyceraldehyde-3-phosphate dehydrogenase (GAPDH)--one of the "housekeeping genes", and the number of cDNA copies of 5-HT(1A) receptor in the sample. To evaluate the number of cDNA copies of the receptor and GAPDH, the fluorescence intensity of PCR-product was calibrated using genomic DNA-standard of a known concentration. The intensity of 5-HT(1A) receptor gene expression was corrected by genomic DNA contamination and was evaluated as a number of copies of 5-HT(1A) receptor cDNA per 100 copies of GAPDH cDNA. Using this method an increase of 5-HT(1A) receptor gene expression in the frontal cortex and amygdala in monoamine oxidase A knockout mice was shown.

Altered responsiveness of serotonin receptor subtypes following long-term cannabinoid treatment.

This study examined the effects of long-term cannabinoid administration on the responsivity of 5-HT1A and 5-HT2A receptors, which have been implicated in depression. Animals received 12 d administration of the potent cannabinoid receptor agonist HU-210 (100 microg/kg), following which they were monitored on their behavioural, physiological and hormonal responses to a single challenge of a 5-HT1A and 5-HT2A receptor agonist, 8-OH-DPAT (0.3 mg/kg) and DOI (1 mg/kg) respectively. Chronic HU-210 treatment lead to a significant enhancement of DOI-induced wet-dog shakes, but a reduction of DOI-induced back muscle contractions. DOI-induced corticosterone release was unaffected by HU-210 treatment. The hyperthermic response to DOI appeared to be potentiated by long-term HU-210 treatment, as 50% of these subjects died from an apparent serotonin syndrome with core temperatures exceeding 43 degrees C. The 8-OH-DPAT-induced hypothermic response and elevation of corticosterone were both significantly attenuated by long- term HU-210 treatment. These data imply that chronic cannabinoid treatment may up-regulate 5-HT2A receptor activity while concurrently down-regulating 5-HT1A receptor activity, a finding similar to that sometimes observed in depression. This may partially explain the association between excessive cannabis consumption and the induction of affective disease.

Serotonergic regulation of the orexin/hypocretin neurons through the 5-HT1A receptor.

Both orexin and serotonin (5-HT) have important roles in the regulation of sleep-wakefulness, as well as in feeding behavior. We examined the effects of 5-HT on orexin/hypocretin neurons, using hypothalamic slices prepared from orexin/enhanced green fluorescent protein (EGFP) transgenic mice in which EGFP is expressed exclusively in orexin neurons. Patch-clamp recording from EGFP-expressing cells showed that 5-HT hyperpolarized all orexin neurons in a concentration-dependent manner. The response was inhibited by the 5-HT1A receptor antagonist WAY100635. A 5-HT1A receptor agonist, 8-hydroxy-2-(dl-N-propyl-amino)tetralin, also evoked hyperpolarization on orexin neurons with potency comparable with 5-HT. A low concentration of Ba2+ (30 microM) inhibited 5-HT-induced hyperpolarization. Single-channel recording revealed that the conductance of 5-HT-induced channel activity was 33.8 pS, which is in good agreement with that of the G-protein-coupled inward rectifier potassium channel (GIRK). Moreover, 5-HT1A receptor-like immunoreactivity was observed on orexin neurons, and 5-HT transporter immunoreactive nerve endings are in close apposition to orexin neurons. Intracerebroventricular injection of the 5-HT1A receptor-selective antagonist WAY100635 (100 ng) increased locomotor activity during the latter half of dark phase in wild-type mice but not in orexin/ataxin-3 mice in which orexin neurons are specifically ablated, suggesting that activation of orexin neurons is necessary for the WAY100635-induced increase in locomotor activity. These results indicate that 5-HT hyperpolarizes orexin neurons through the 5-HT1A receptor and subsequent activation of the GIRK and that this inhibitory serotonergic input to the orexin neurons is likely to be important for the physiological regulation of this neuropeptide system.