Insights into serotonergic and antioxidant mechanisms involved in antidepressant-like action of 2-phenyl-3-(phenylselanyl)benzofuran in mice.

Monoaminergic and oxidative dysfunctions have been reported to play a role in depression. The present study investigated the antioxidant potential as well as the antidepressant-like action of 2-phenyl-3-(phenylselanyl)benzofuran (SeBZF1) in male Swiss mice. Time and dose-response curves were analyzed with the forced swim (FST) and tail suspension (TST) tests, in which SeBZF1 elicited antidepressant-like effects. Serotonergic mechanisms were investigated in the TST. The pre-administration of WAY100635 (selective 5-HT1A receptor antagonist, 0.1 mg/kg, subcutaneous route), ketanserin (5-HT2A/2C receptor antagonist, 1 mg/kg, intraperitoneal route, i.p.), and chlorophenylalaninemethyl ester (p-CPA) (selective tryptophan hydroxylase inhibitor, 100 mg/kg, i.p., for 4 days), but not of ondansetron (selective 5-HT3 receptor antagonist, 1 mg/kg, i.p.), abolished the antidepressant-like action of SeBZF1 (50 mg/kg, intragastric route, i.g.). Co-administration of sub-effective doses of SeBZF1 (1 mg/kg, i.g.) and fluoxetine (5 mg/kg, i.p., selective serotonin reuptake inhibitor) was effective in producing anti-immobility effects in the TST, revealing a synergistic effect. Besides, p-CPA induced hippocampal oxidative stress, characterized by a reduction of total thiols and lipoperoxidation, which was reversed by SeBZF1 (50 mg/kg). The in vitro screening of the antioxidant action of SeBZF1 in brain tissue reinforced these results. Lastly, SeBZF1 did not cause systemic toxicity at a high dose (300 mg/kg). In summary, the present study demonstrated that SeBZF1 exerted antidepressant-like action in male mice which appears to be mediated by the serotonergic system. Moreover, SeBZF1 elicited in vitro antioxidant action in brain tissue, attenuated the hippocampal oxidative damage induced by 5-HT depletion in mice and showed no toxic signs.

Modality selective roles of pro-nociceptive spinal 5-HT2A and 5-HT3 receptors in normal and neuropathic states.

Descending brainstem control of spinal nociceptive processing permits a dynamic and adaptive modulation of ascending sensory information. Chronic pain states are frequently associated with enhanced descending excitatory drive mediated predominantly through serotonergic neurones in the rostral ventromedial medulla. In this study, we examine the roles of spinal 5-HT2A and 5-HT3 receptors in modulating ascending sensory output in normal and neuropathic states. In vivo electrophysiology was performed in anaesthetised spinal nerve ligated (SNL) and sham-operated rats to record from wide dynamic range neurones in the ventral posterolateral thalamus. In sham rats, block of spinal 5-HT3Rs with ondansetron revealed tonic facilitation of noxious punctate mechanical stimulation, whereas blocking 5-HT2ARs with ketanserin had minimal effect on neuronal responses to evoked stimuli. The inhibitory profiles of both drugs were altered in SNL rats; ondansetron additionally inhibited neuronal responses to lower intensity punctate mechanical stimuli and noxious heat evoked responses, whereas ketanserin inhibited innocuous and noxious evaporative cooling evoked responses. Neither drug had any effect on dynamic brush evoked responses nor on spontaneous firing rates in both sham and SNL rats. These data identify novel modality and intensity selective facilitatory roles of spinal 5-HT2A and 5-HT3 receptors on sensory neuronal processing within the spinothalamic-somatosensory cortical pathway.

Assessment of the possible roles of SB-269970 versus ketanserin on carbon tetrachloride-induced liver fibrosis in rats: Oxidative stress/TGF-ß1-induced HSCs activation pathway.

BACKGROUND: In liver fibrosis, a major morbid and mortal disease, oxidative stress motivation of hepatic stellate cells (HSCs)-into myofibroblasts terminated in collagen deposition remain the key pathophysiological deal. Serotonin (5-HT) through its HSCs-expressed receptors, especially 5-HT2A and 7, shows crucial events in fibrogenesis of chronic liver diseases. Molecular hepatic oxidative stress-fibrotic roles of 5-HT2A and 7 receptors antagonists (ketanserin and SB-269970 respectively) are still a challenging issue. METHODS: Seven groups of adult male Wistar rats (n=10) were used. A carbon tetrachloride (CCl4) solution was injected intraperitoneally twice weekly for 6 weeks. On the 7th week, rats developed liver fibrosis were treated either by ketanserin (1mg/kg/day, ip) or SB-269970 (2mg/kg/day, ip) for 14days. Survival rates, and serum alanine aminotransferase (ALT) and aspartate aminotransferase (AST) levels in addition to hepatic malondialdehyde (MDA) and reduced glutathione (GSH) levels, superoxide dismutase (SOD) and catalase (CAT) activities, and transforming growth factor-beta1 (TGF-ß1) and procollagen type I N-terminal propeptide (PINP) levels, beside the hepatic histopathological fibrotic changes, were evaluated. RESULTS: In CCl4-challenged rats, each therapeutic approach showed significant reductions in elevated serum ALT, and AST levels, hepatic MDA, TGF-ß1, and PINP levels, and histopathological hepatic fibrotic scores as well as significant elevations in survival rates, reduced hepatic GSH levels, and SOD, and CAT activities. Remarkably, significant ameliorative measurements were observed in SB-269970 treated group. CONCLUSION: Blockade of 5-HT2A and 7 receptors each alone could be a future reliable therapeutic approach in liver fibrosis through a reduction in oxidative stress/TGF-ß1-induced HSCs activation pathway.

Dreamlike effects of LSD on waking imagery in humans depend on serotonin 2A receptor activation.

RATIONALE: Accumulating evidence indicates that the mixed serotonin and dopamine receptor agonist lysergic acid diethylamide (LSD) induces an altered state of consciousness that resembles dreaming. OBJECTIVES: This study aimed to test the hypotheses that LSD produces dreamlike waking imagery and that this imagery depends on 5-HT2A receptor activation and is related to subjective drug effects. METHODS: Twenty-five healthy subjects performed an audiorecorded guided mental imagery task 7 h after drug administration during three drug conditions: placebo, LSD (100 mcg orally) and LSD together with the 5-HT2A receptor antagonist ketanserin (40 mg orally). Cognitive bizarreness of guided mental imagery reports was quantified as a standardised formal measure of dream mentation. State of consciousness was evaluated using the Altered State of Consciousness (5D-ASC) questionnaire. RESULTS: LSD, compared with placebo, significantly increased cognitive bizarreness (p < 0.001). The LSD-induced increase in cognitive bizarreness was positively correlated with the LSD-induced loss of self-boundaries and cognitive control (p < 0.05). Both LSD-induced increases in cognitive bizarreness and changes in state of consciousness were fully blocked by ketanserin. CONCLUSIONS: LSD produced mental imagery similar to dreaming, primarily via activation of the 5-HT2A receptor and in relation to loss of self-boundaries and cognitive control. Future psychopharmacological studies should assess the differential contribution of the D2/D1 and 5-HT1A receptors to cognitive bizarreness.

Serotonergic and dopaminergic systems are implicated in antidepressant-like effects of chotosan, a Kampo formula, in mice.

We previously demonstrated that chotosan (CTS), a traditional herbal formula called Kampo medicine, improves diabetes-induced cognitive deficits. In the present study, we investigated the antidepressant-like effects of CTS in mice. The administration of CTS (1.0 g/kg, for 3 days) decreased the immobility time in the forced-swim test, and this decrease was prevented by the prior administration of sulpiride (an antagonist of D2/3 receptors) and WAY100635 (an antagonist of 5-HT1A receptors). None of the treatments tested altered the locomotor activity of mice. These results suggest that CTS exerts antidepressant-like effects through changes in the serotonergic and dopaminergic systems.

Brief Isolation Changes Nociceptive Behaviors and Compromises Drug Tests in Mice.

Herding with a litter is known to comfort rodents, whereas isolation and grouping with noncagemates provoke stress. The effects of stress induced by isolation and grouping with noncagemates on pain responses, and their underlying mechanisms remain elusive. We assessed the effect of isolation, a common condition during behavioral tests, and of grouping on defecation and pain behaviors of mice. Fecal pellets were counted 2 hours after exposure to the test chamber. It is significantly more in the isolated mice than in the grouped mice. Hindpaw withdrawal threshold and withdrawal latency were adopted as the indicatives of mechanical and thermal pain sensitivities, respectively. Interestingly, isolated mice showed higher pain thresholds than mice grouping with cagemates, and even those with noncagemates, indicating analgesic effects. Such effects were reduced by intrathecal injection of 0.01 mg/kg of naloxone (opioid receptor antagonist), atosiban (oxytocin and vasopressin receptor antagonist), and ketanserin (5-HT receptor antagonist). Intraperitoneal delivery of 1 mg/kg of naloxone and atosiban, but not ketanserin, also alleviated the isolation-induced analgesic effects. In contrast, these drugs at the same dose had no significant effect on the mice grouping with cagemates. In addition, the effect of morphine on thermal pain was more robust in the mice grouping with cagemates than in the isolated mice. These data demonstrated that brief isolation caused analgesia, mediated by endogenous opioidergic, oxytocinergic, and serotonergic pathways. These results indicate that isolation during pain behavioral tests can affect pain responses and the efficacy of drugs; thus, nociception tests should be conducted in grouping.

Tolerance to LSD and DOB induced shaking behaviour: differential adaptations of frontocortical 5-HT(2A) and glutamate receptor binding sites.

Serotonergic hallucinogens, such as lysergic acid diethylamide (LSD) and dimethoxy-bromoamphetamine (DOB), provoke stereotype-like shaking behaviour in rodents, which is hypothesised to engage frontocortical glutamate receptor activation secondary to serotonin2A (5-HT2A) related glutamate release. Challenging this hypothesis, we here investigate whether tolerance to LSD and DOB correlates with frontocortical adaptations of 5-HT2A and/or overall-glutamate binding sites. LSD and DOB (0.025 and 0.25 mg/kg, i.p.) induce a ketanserin-sensitive (0.5 mg/kg, i.p., 30-min pretreatment) increase in shaking behaviour (including head twitches and wet dog shakes), which with repeated application (7× in 4 ds) is undermined by tolerance. Tolerance to DOB, as indexed by DOB-sensitive [(3)H]spiroperidol and DOB induced [(35)S]GTP-gamma-S binding, is accompanied by a frontocortical decrease in 5-HT2A binding sites and 5-HT2 signalling, respectively; glutamate-sensitive [(3)H]glutamate binding sites, in contrast, remain unchanged. As to LSD, 5-HT2 signalling and 5-HT2A binding, respectively, are not or only marginally affected, yet [(3)H]glutamate binding is significantly decreased. Correlation analysis interrelates tolerance to DOB to the reduced 5-HT2A (r=.80) as well as the unchanged [(3)H]glutamate binding sites (r=.84); tolerance to LSD, as opposed, shares variance with the reduction in [(3)H]glutamate binding sites only (r=.86). Given that DOB and LSD both induce tolerance, one correlating with 5-HT2A, the other with glutamate receptor adaptations, it might be inferred that tolerance can arise at either level. That is, if a hallucinogen (like LSD in our study) fails to induce 5-HT2A (down-)regulation, glutamate receptors (activated postsynaptic to 5-HT2A related glutamate release) might instead adapt and thus prevent further overstimulation of the cortex.

Serotonergic mechanism of the relieving effect of bee venom acupuncture on oxaliplatin-induced neuropathic cold allodynia in rats.

BACKGROUND: Oxaliplatin, an important chemotherapy drug for advanced colorectal cancer, often induces peripheral neuropathy, especially cold allodynia. Our previous study showed that bee venom acupuncture (BVA), which has been traditionally used in Korea to treat various pain symptoms, potently relieves oxaliplatin-induced cold allodynia in rats. However, the mechanism for this anti-allodynic effect of BVA remains poorly understood. We investigated whether and how the central serotonergic system, a well-known pathway for acupuncture analgesia, mediates the relieving effect of BVA on cold allodynia in oxaliplatin-injected rats. METHODS: The behavioral signs of cold allodynia in Sprague-Dawley (SD) rats were induced by a single injection of oxaliplatin (6 mg/kg, i.p.). Before and after BVA treatment, the cold allodynia signs were evaluated by immersing the rat's tail into cold water (4°C) and measuring the withdrawal latency. For BVA treatment, a diluted BV (0.25 mg/kg) was subcutaneously administered into Yaoyangguan (GV3) acupoint, which is located between the spinous processes of the fourth and the fifth lumbar vertebra. Serotonin was depleted by a daily injection of DL-p-chlorophenylalanine (PCPA, 150 mg/kg, i.p.) for 3 days. The amount of serotonin in the spinal cord was measured by ELISA. Serotonergic receptor antagonists were administered intraperitoneally or intrathecally before BVA treatment. RESULTS: The serotonin levels in the spinal cord were significantly increased by BVA treatment and such increase was significantly reduced by PCPA. This PCPA pretreatment abolished the relieving effect of BVA on oxaliplatin-induced cold allodynia. Either of methysergide (mixed 5-HT1/5-HT2 receptor antagonist, 1 mg/kg, i.p.) or MDL-72222 (5-HT3 receptor antagonist, 1 mg/kg, i.p) blocked the anti-allodynic effect of BVA. Further, an intrathecal injection of MDL-72222 (12 µg) completely blocked the BVA-induced anti-allodynic action, whereas NAN-190 (5-HT1A receptor antagonist, 15 µg, i.t.) or ketanserin (5-HT2A receptor antagonist, 30 µg, i.t.) did not. CONCLUSIONS: These results suggest that BVA treatment alleviates oxaliplatin-induced acute cold allodynia in rats via activation of the serotonergic system, especially spinal 5-HT3 receptors. Thus, our findings may provide a clinically useful evidence for the application of BVA as an alternative therapeutic option for the management of peripheral neuropathy, a dose-limiting side effect that occurs after an administration of oxaliplatin.

Effect of 5-HT(2A) receptor antagonists on blood flow in the carotid vessels upon elevation of serotonin level.

We studied the ability of predominantly 5-HT2A receptor antagonists to prevent a serotonin-induced change of blood flow in the carotid vessels of rats with experimental serotonin-induced spasm. Ritanserin, ketanserin, and 5-HT2A receptor antagonist RU-476 reduced the effect of serotonin on the blood fl ow velocity in the internal carotid artery by 2.3, 1.7, and 2.6 times, respectively.

Ketanserin, a serotonin 2A receptor antagonist, alleviates ischemia-related biliary fibrosis following donation after cardiac death liver transplantation in rats.

Biliary fibrosis is a major complication after donation after cardiac death (DCD) liver transplantation. In this process, the roles of serotonin [5-hydroxytryptamine (5-HT)] and the 5-HT2A receptor subtype are still unknown. In this study, we analyzed markers of portal fibroblast (PF)/myofibroblast (MF) transdifferentiation such as transforming growth factor ß1 (TGF-ß1), phosphorylated smad2/3, α-smooth muscle actin (α-SMA), collagen I, and collagen III in a primary culture system of PFs after the administration of 5-HT or 5-HT plus ketanserin (a selective 5-HT2A receptor antagonist). A rat DCD transplant model was established with 30 minutes of warm ischemia and 4 hours of cold ischemia during organ procurement. Recipients were intraperitoneally injected with ketanserin (1 mg·kg(-1)·day(-1)) or normal saline. Grafts without in situ warm ischemia instead of minimal cold storage (30 minutes) served as controls. The serum biochemistry, the liver contents of 5-HT and hydroxyproline (HYP), and the expression of fibrosis-related genes (including TGF-ß1, matrix metalloproteinase 2, procollagen α1, and α-SMA messenger RNA) were determined. The extent of biliary fibrosis was also assessed histopathologically. The results indicated that ketanserin inhibited 5-HT-activated TGF-ß1-smad2/3 signaling in vitro and thereby depressed the MF conversion of PFs. Rats receiving DCD livers showed increased liver contents of 5-HT and HYP, impaired biliary function, up-regulation of fibrosis-related genes, and aggravated biliary fibrosis. However, these phenomena were alleviated by treatment with ketanserin. We concluded that the profibrotic activity of 5-HT occurred through the activation of TGF-ß1 signaling and the 5-HT2A receptor. Thus, these data suggest that the 5-HT2A receptor may be a potential therapeutic target for ischemia-related biliary fibrosis after DCD liver transplantation.

Citral: a monoterpene with prophylactic and therapeutic anti-nociceptive effects in experimental models of acute and chronic pain.

Citral (3,7-dimethyl-2,6-octadienal) is an open-chain monoterpenoid present in the essential oils of several medicinal plants. The aim of this work was to evaluate the effects of orally administered citral in experimental models of acute and chronic nociception, inflammation, and gastric ulcers caused by non-steroidal anti-inflammatory drugs (NSAIDs). Oral treatment with citral significantly inhibited the neurogenic and inflammatory pain responses induced by intra-plantar injection of formalin. Citral also had prophylactic and therapeutic anti-nociceptive effects against mechanical hyperalgesia in plantar incision surgery, chronic regional pain syndrome, and partial ligation of sciatic nerve models, without producing any significant motor dysfunction. In addition, citral markedly attenuated the pain response induced by intra-plantar injection of glutamate and phorbol 12-myristate 13-acetate (PMA, a protein kinase C activator), as well as by intrathecal (i.t.) injection of ionotropic and metabotropic glutamate receptor agonists (N-methyl-D-aspartic acid [NMDA] and 1-amino-1,3-dicarboxycyclopentane [trans-ACPD], respectively), substance P, and cytokine tumour necrosis factor-α. However, citral potentiated behaviours indicative of pain caused by i.t., but not intra-plantar, injection of a transient receptor potential vanilloid receptor type 1 (TRPV1) agonist. Finally, the anti-nociceptive action of citral was found to involve significant activation of the 5-HT2A serotonin receptor. The effect of citral was accompanied by a gastro-protective effect against NSAID-induced ulcers. Together, these results show the potential of citral as a new drug for the treatment of pain.

Psilocybin-induced deficits in automatic and controlled inhibition are attenuated by ketanserin in healthy human volunteers.

The serotonin-2A receptor (5-HT(2A)R) has been implicated in the pathogenesis of schizophrenia and related inhibitory gating and behavioral inhibition deficits of schizophrenia patients. The hallucinogen psilocybin disrupts automatic forms of sensorimotor gating and response inhibition in humans, but it is unclear so far whether the 5-HT(2A)R or 5-HT(1A)R agonist properties of its bioactive metabolite psilocin account for these effects. Thus, we investigated whether psilocybin-induced deficits in automatic and controlled inhibition in healthy humans could be attenuated by the 5-HT(2A/2C)R antagonist ketanserin. A total of 16 healthy participants received placebo, ketanserin (40 mg p.o.), psilocybin (260 µg/kg p.o.), or psilocybin plus ketanserin in a double-blind, randomized, and counterbalanced order. Sensorimotor gating was measured by prepulse inhibition (PPI) of the acoustic startle response. The effects on psychopathological core dimensions and behavioral inhibition were assessed by the altered states of consciousness questionnaire (5D-ASC), and the Color-Word Stroop Test. Psilocybin decreased PPI at short lead intervals (30 ms), increased all 5D-ASC scores, and selectively increased errors in the interference condition of the Stroop Test. Stroop interference and Stroop effect of the response latencies were increased under psilocybin as well. Psilocybin-induced alterations were attenuated by ketanserin pretreatment, whereas ketanserin alone had no significant effects. These findings suggest that the disrupting effects of psilocybin on automatic and controlled inhibition processes are attributable to 5-HT(2A)R stimulation. Sensorimotor gating and attentional control deficits of schizophrenia patients might be due to changes within the 5-HT(2A)R system.

p-Hydroxyamphetamine causes prepulse inhibition disruption in mice: contribution of serotonin neurotransmission.

p-Hydroxyamphetamine (p-OHA) has been shown to have a number of pharmacological actions, including causing abnormal behaviors such as increased locomotor activity and head-twitch response in rodents. We have recently reported that intracerebroventricular (i.c.v.) administration of p-OHA dose-dependently induces prepulse inhibition (PPI) disruption in mice, which is attenuated by pretreatment with haloperidol, clozapine or several dopaminergic agents. Haloperidol and clozapine have affinities for serotonergic (especially 5-HT(2A)) receptors. To investigate the involvement of the central serotonergic systems in p-OHA-induced PPI disruption, herein we tested several serotonergic agents to determine their effects on p-OHA-induced PPI disruption. p-OHA-induced PPI disruption was attenuated by pretreatment with 5,7-dihydroxytryptamine (5,7-DHT, a neurotoxin which targets serotonin-containing neurons) and p-chlorophenylalanine (PCPA, a serotonin synthesis inhibitor). p-OHA-induced PPI disruption was also attenuated by pretreatment with ketanserin (a 5-HT(2A/2C) receptor antagonist) and MDL100,907 (a selective 5-HT(2A) receptor antagonist). These data suggest that p-OHA-induced PPI disruption may involve increased serotonin release into the synaptic cleft, which then interacts with the post-synaptic 5-HT(2A) receptor.

Pharmacological characterizations of memantine-induced disruption of prepulse inhibition of the acoustic startle response in mice: involvement of dopamine D2 and 5-HT2A receptors.

It has recently been reported that psychotic symptoms in patients such as those with Parkinson's disease dementia (PDD) and Lewy body dementia (LBD) may worsen following treatment with memantine, a non-competitive NMDA receptor antagonist. Prepulse inhibition (PPI) of the acoustic startle response (ASR) is used as a measure for sensorimotor gating and it has been reported that PPI is disrupted by memantine. However, the mechanism of memantine-induced PPI disruption remains unclear. In the present study, we investigated the effects of memantine on PPI of the ASR in mice. Memantine (1.25-20mg/kg, intraperitoneally) increased the ASR and dose-dependently decreased PPI for all prepulse intensities tested. This effect of memantine on PPI was attenuated by pretreatment with the antipsychotics clozapine (3 and 6 mg/kg), risperidone (0.3mg/kg) and haloperidol (0.5mg/kg), the selective D(2) antagonist sulpiride (40 mg/kg) and 5-HT(2A/2C) antagonist ketanserin (2 and 4 mg/kg) but not with the selective D(1) antagonist SCH23390 (0.05 and 0.1mg/kg). Clozapine (6 mg/kg) and risperidone (0.3 mg/kg) significantly attenuated the increased startle amplitude in the memantine-treated groups. These results suggest that involvement of dopaminergic and/or serotonergic neurotransmission may play a crucial role in memantine-induced PPI disruption, and additionally, indicate that blockade of either the D(2) or 5-HT(2A) receptor may prevent disruption of PPI induced by memantine in mice. Conceivably, memantine may exacerbate psychotic symptoms in patients with PDD and LBD.

PPI deficit induced by amphetamine is attenuated by the histamine H1 antagonist pyrilamine, but is exacerbated by the serotonin 5-HT2 antagonist ketanserin.

RATIONALE: Prepulse inhibition (PPI) of the startle response is a classic model of sensorimotor gating. Robust PPI impairments can be induced by dopamine agonists such as the indirect agonist amphetamine. The antipsychotic clozapine can attenuate PPI impairment induced by dopamine agonists. Clozapine is a complex drug with antagonistic effects on a variety of receptors, including serotonin and histamine. The relative contribution of its component actions to its efficacy is still unclear. OBJECTIVES: To better characterize the role of histamine and serotonin receptors in the modulation of PPI in rats, we studied the effects of the H(1) histamine antagonist pyrilamine (10, 20, and 40 mg/kg) on amphetamine-induced (1 mg/kg) PPI deficits (Experiment 1); and the interaction of pyrilamine (20 mg/kg) with the 5-HT(2) antagonist ketanserin (1 and 2 mg/kg) on the amphetamine-induced PPI disruption (Experiment 2). METHODS: Tactile startle stimuli consisted of 30 PSI air-puffs. Three acoustic prepulse intensity levels were used: 68, 71, and 77 dB, presented on a 65-dB background noise. In both experiments, all animals received all drug doses and combinations with different counterbalanced orders. RESULTS: Pyrilamine (20 mg/kg) was effective in counteracting the PPI impairment caused by amphetamine administration, whereas ketanserin exacerbated the amphetamine-induced PPI deficit. CONCLUSIONS: Based on its ability to reverse amphetamine-induced PPI deficits, blockade of histamine H(1) receptors seems to contribute to the therapeutic effect of the antipsychotic clozapine. Serotonin 5-HT(2)-receptor blockade, though, does not appear to contribute to this effect, and may in fact detract from it.

Oleamide administered into the nucleus accumbens shell regulates feeding behaviour via CB1 and 5-HT2C receptors.

The central nervous system control of food intake has been extensively studied, hence, several neurotransmitter systems regulating this function are now clearly identified, for example, the endocannabinoid and serotoninergic systems. The former stimulates feeding while the latter inhibits it. Oleamide (Ole) is a cannabimimetic molecule affecting both systems. In this work, we tested the orexigenic and anorectic potential of Ole when administered into the nucleus accumbens shell (NAcS), a brain region that has been related to the orexigenic effects of cannabinoids. Additionally, we tested if Ole administered into this nucleus affects the activity of the hypothalamic nuclei involved in feeding behaviour, just as other cannabinoids do. We found a hyperphagic effect of Ole that is mediated through CB1 activation. The combination of Ole and the CB1 antagonist, AM251, produced a hypophagia that was fully blocked by SB212084, a 5-HT2C receptor antagonist. We also show that blockade of 5-HT2C and 5-HT2A receptors in the NAcS stimulates food intake. Finally, the combination of Ole and AM251 activates hypothalamic nuclei, an effect also blocked by SB242084. In conclusion, we show, for the first time, that Ole administered into the NAcS has a dual effect on feeding behaviour, acting through cannabinoid and serotonin receptors. These effects probably result from a downstream interaction with the hypothalamus.

Horse chestnut extract contracts bovine vessels and affects human platelet aggregation through 5-HT(2A) receptors: an in vitro study.

Extract from seeds and bark of horse chestnut (Aesculus hippocastanum L) is used as an herbal medicine against chronic venous insufficiency. The effect and mechanism of action on veins, arteries, and platelets are not fully understood. The aim of this study was to investigate the effects and mechanisms of action of horse chestnut on the contraction of bovine mesenteric veins and arteries, and human platelet aggregation. Contraction studies showed that horse chestnut extract dose-dependently contracted both veins and arteries, with the veins being the most sensitive. Contraction of both veins and arteries were significantly inhibited by the 5-HT(2A) receptor antagonist ketanserin. No effect on contraction was seen with the cyclooxygenase inhibitor indomethacin, the alpha(1) receptor antagonist prazosin or the angiotensin AT(1) receptor antagonist saralasin neither in veins nor arteries. ADP-induced human platelet aggregation was significantly reduced by horse chestnut. A further reduction was seen with the extract in the presence of ketanserin. In conclusion, horse chestnut contraction of both veins and arteries is, at least partly, mediated through 5-HT(2A) receptors. Human platelet aggregation is reduced by horse chestnut. The clinical importance of these findings concerning clinical use, possible adverse effects, and drug interactions remains to be investigated.

Antidepressant-like action of the ethanolic extract from Tabebuia avellanedae in mice: evidence for the involvement of the monoaminergic system.

The antidepressant-like effect of the ethanolic extract obtained from barks of Tabebuia avellanedae, a plant widely employed in folk medicine, was investigated in two predictive models of depression: forced swimming test (FST) and tail suspension test (TST) in mice. Additionally, the mechanisms involved in this antidepressant-like action and the effects of the association of the extract with the antidepressants fluoxetine, desipramine and bupropion in the TST were investigated. The extract from T. avellanedae produced an antidepressant-like effect, in the FST (100 mg/kg, p.o.) and in the TST (10-300 mg/kg, p.o.), without accompanying changes in ambulation when assessed in the open-field test. The anti-immobility effect of the extract (30 mg/kg, p.o.) in the TST was prevented by pre-treatment of mice with ketanserin (5 mg/kg, i.p., a preferential 5-HT(2A) receptor antagonist), prazosin (1 mg/kg, i.p., an alpha(1)-adrenoceptor antagonist), yohimbine (1 mg/kg, i.p., an alpha(2)-adrenoceptor antagonist), propranolol (2 mg/kg, i.p., a beta-adrenoceptor antagonist), sulpiride (50 mg/kg, i.p., a dopamine D(2) receptor antagonist) and SCH23390 (0.05 mg/kg, s.c., a dopamine D(1) receptor antagonist). The combined administration of a subeffective dose of WAY100635 (0.1 mg/kg, s.c., a selective 5-HT(1A) receptor antagonist) and a subeffective dose of the extract (1 mg/kg, p.o.) produced a significant reduction in the immobility time in the TST. In addition, the combination of fluoxetine (1 mg/kg, p.o.), desipramine (0.1 mg/kg, p.o.), or bupropion (1 mg/kg, p.o.) with a subeffective dose of the extract (1 mg/kg, p.o.) produced a synergistic antidepressant-like effect in the TST, without causing hyperlocomotion in the open-field test. It may be concluded that the extract from T. avellanedae produces an antidepressant-like effect in the FST and in the TST that is dependent on the monoaminergic system. Taken together, our results suggest that T. avellanedae deserves further investigation as a putative alternative therapeutic tool that could help the conventional pharmacotherapy of depression.

Impact of the 5-HT3 receptor channel system for insulin secretion and interaction of ginger extracts.

The relevance of serotonin and in particular that of 5-HT(3) receptors is unequivocal with respect to emetic/antiemetic effects, but it is controversial with respect to antidiabetic effects. The effects of tropisetron (5-HT(3) receptor antagonist) and various ginger (Zingiber officinale) extracts (known to interact with the 5-HT(3) receptor channel system) were investigated. Serotonin (32 to 500 microM) inhibits insulin release (RIA) from INS-1 cells which is reversed by tropisetron (10 to 100 microM) and two different ginger extracts (spissum and an oily extract). Their effects are obvious even in the absence of serotonin but are more pronounced in its presence (doubled to tripled). Specific 5-HT(3) binding sites are present in INS-1 cells using 0.4 nM [3H] GR65630 in displacement experiments. The in vitro data with respect to ginger are corroborated by in vivo data on glucose-loaded rats showing that blood glucose (Glucoquant) is decreased by approximately 35% and plasma insulin (RIA) is increased by approximately 10%. Both the spissum extract and the oily ginger extract are effective in two other models: they inhibit [(14)C] guanidinium uptake into N1E-115 cells (model of 5-HT(3) effects) and relax rat ileum both directly and as a serotonin antagonistic effect. Other receptors addressed by ginger are 5-HT(2) receptors as demonstrated by using methysergide and ketanserin. They weakly antagonize the serotonin effect as well. It may be concluded that serotonin and in particular the 5-HT(3) receptor channel system are involved in modulating insulin release and that tropisetron and various ginger extracts can be used to improve a diabetic situation.

Eugenosedin-A prevents hyperglycaemia, hyperlipidaemia and lipid peroxidation in C57BL/6J mice fed a high-fat diet.

OBJECTIVES: Eugenosedin-A is a serotonin (5-hydroxytryptamine; 5-HT) 5-HT(1B/2A) and alpha(1)/alpha(2)/beta(1)-adrenoceptor blocker with anti-oxidative, anti-inflammatory and free-radical scavenging activities. Previous reports demonstrated that 5-HT(2A) blockers could diminish hyperlipidaemia. This study therefore aimed to investigate the possible uses and mechanisms of eugenosedin-A and other agents in treating hyperlipidaemia. METHODS: C57BL/6J mice were randomly divided into seven groups, fed a regular diet or a high-fat diet alone or supplemented with one of five agents: eugenosedin-A, ketanserin, prazosin, propranolol or atorvastatin (5 mg/kg p.o.) for 8 weeks. KEY FINDINGS: Compared with the regular diet, the mice fed the high-fat diet had significantly higher body weight and glucose, insulin and lipid levels. Brain malondialdehyde concentration was increased and liver glutathione peroxidase activity decreased. Addition of eugenosedin-A to the high-fat diet resulted in less weight gain and reduced hyperglycaemia, hyperinsulinaemia and hyperlipidaemia. Lipid and glucose homeostasis were related to decreased hepatic lipogenesis mRNAs and proteins (sterol regulatory element binding protein 1a, fatty acid synthase, sterol-CoA desaturase) and restored adipose peroxisome proliferator-activated receptor gamma expression. Eugenosedin-A also enhanced low-density lipoprotein receptor mRNA expression. CONCLUSIONS: Eugenosedin-A may improve plasma lipid metabolism by increasing low-density lipoprotein receptor and peroxisome proliferator-activated receptor gamma expression and diminishing sterol regulatory element binding protein 1a, fatty acid synthase and sterol-CoA desaturase. Reduction of plasma glucose and lipid levels may, in turn, reduce insulin concentration, which would explain the marked improvement in obesity-related hyperglycaemia and hyperlipidaemia. Furthermore, eugenosedin-A affected malondialdehyde concentration and glutathione peroxidase activity, suggesting it may have anti-peroxidation effects in mice fed a high-fat diet.