Retinal serotonin, eye growth and myopia development in chick

Myopia (short-sightedness) is a visual problem associated with excessive eye growth and vitreous chamber expansion. Within the eye serotonin (5-hydroxytryptamine, 5-HT) appears to have a variety of effects, it alters retinal amacrine cell processing, increases intraocular pressure, constricts ocular blood vessels, and is also mitogenic. This study sought to determine the role of the retinal serotonin system in eye growth regulation. Myopia was produced in 7-day-old chicks using -15 D spectacle lenses (LIM) and form deprivation (FDM). The effect on LIM and FDM of daily intravitreal injections of a combination of 5-HT receptor antagonists (1, 10, 50 mu M), 5-HT2 selective antagonist (Mianserin 0.5, 20 mu M) were assessed. Counts were performed of serotonin and tyrosine hydroxylase positive neurons and the relative density used to account for areal changes due to eye growth. The effect of LIM and lens-induced hyperopia (LIH) on the numbers of 5-HT-containing amacrine cells in the retina were then determined. The combination of the 5-HT receptor antagonists inhibited LIM by approximately half (1 mu M RE: -7.12 +/- 1.0 D, AL: 0.38 +/- 0.06 mm vs. saline RE: -13.19 +/- 0.65 D, AL: 0.64 +/- 0.03 mm. RE: p < 0.01, AL: p < 0.01), whereas FDM was not affected (1 mu M RE: -8.88 +/- 1.10 D). These data suggest that serotonin has a stimulatory role in LIM, although high doses of serotonin were inhibitory (1 mu M RE: -9.30 +/- 1.34 D). 5-HT immunoreactivity was localised to a subset of amacrine cell bodies in the inner nuclear layer of the retina, and to two synaptic strata in the inner plexiform layer. LIM eyes had increased numbers of 5-HT-containing amacrine cells in the central retina (12.5%). Collectively, these results suggest that manipulations to the serotonin system can alter the eye growth process but the role of the transmitter system within this process remains unclear. (c) 2005 Elsevier Ltd. All rights reserved.

Fluoxetine induces preventive and complex effects against colon cancer development in epithelial and stromal areas in rats

Fluoxetine (FIX) is a drug commonly used as antidepressant. However, its effects on tumorigenesis remain controversial. Aiming to evaluate the effects of FIX treatment on early malignant changes, we analyzed serotonin (5-HT) metabolism and recognition, aberrant crypt foci (ACF), proliferative process, microvessels, vascular endothelial growth factor (VEGF), and cyclooxygenase-2 (COX-2) expression in colon tissue. Male Wistar rats received a daily FLX-gavage (30 mg kg(-1)) and, a single dose of 1.2 dimethylhydrazine (DMH; i.p., 125 mg kg(-1)). After 6 weeks of FIX-treatment, our results revealed that FIX and nor-fluoxetine (N-FIX) are present in colon tissue, which was related to significant increase in serotonin (5-HT) levels (P < 0.05) possibly through a blockade in SERT mRNA (serotonin reuptake transporter; P < 0.05) resulting in lower 5-hydroxyindoleacetic acid (5-HIAA) levels (P < 0.01) and, 5-HT2C receptor mRNA expressions. FIX-treatment decreased dysplastic ACF development (P < 0.01) and proliferative process (P < 0.001) in epithelia. We observed a significant decrease in the development of malignant microvessels (P < 0.05), VEGF (P < 0.001), and COX-2 expression (P < 0.01). These findings suggest that FIX may have oncostatic effects on carcinogenic colon tissue, probably due to its modulatory activity on 5-HT metabolism and/or its ability to reduce colonic malignant events. (C) 2011 Elsevier Ireland Ltd. All rights reserved.

Identification of regions within the third FnIII-like domain of the IL-5R alpha involved in IL-5 interaction

Previously, two binding sites for interleukin 5 (IL-5) were identified on the IL-5 receptor alpha chain (IL-5R alpha). They are located within the CD loop of the first fibronectin type III (FnIII)-like domain and the EF loop of the second FnIII-like domain. The first binding site was identified by exploiting the different abilities of human IL-5R alpha (hIL-5R alpha) and mouse IL-5R alpha (mIL-5R alpha) to bind hIL-5. Here we show that ovine IL-5 (oIL-5) has the ability to activate the hIL-5R alpha but not the mIL-5R alpha. By using chimeras of the mIL-5R alpha and hIL-5R alpha we demonstrate that residues within the first and third FnIII-like domains of mIL-5R alpha are responsible for this lack of activity. Furthermore, mutation of residues on hIL-5R alpha to mIL-5R alpha within the predicted DE and FG loop regions of the third FnIII domain reduces oIL-5 activity, These results show that regions of the third FnIII domain of IL-5R alpha are involved in binding, in addition to the regions in domains one and two of the IL-5R alpha that were identified in an earlier study. (C) 2000 Academic Press.

The serotonin transporter gene and Parkinson's disease

Dysfunction in the serotonin (5-hydroxytryptamine) system and reduced serotonin concentrations have been reported in patients with Parkinson's disease (PD). Serotonin concentrations in neural tissue are controlled by a presynaptic serotonin transporter protein that is encoded by a single gene. Therefore, we investigated whether a polymorphic region in the serotonin transporter gene is associated with PD. Three variable-number tandem repeat (VNTR) elements of the serotonin transporter gene were detected by polymerase chain reaction, those with 9, 10, 11 and 12 copies of the repeat element. The 10-copy VNTR element was significantly less common in patients with PD than controls in the univariate analysis (p < 0.05). Logistic regression analysis revealed no significant differences between patients (n = 198) and controls (n = 200) in the distribution frequencies of 9-and 12-copy alleles and combined genotypes (odds ratio = 1.20; p = 1.71). A positive family history of PD was a strong predictor of disease risk (odds ratio = 2.98; 95% confidence interval 1.51-5.87; p = 0.001). Although slight differences were observed between patient and control groups, these data suggest that defects in serotonin concentrations in patients with PD are unlikely to be due to polymorphisms in the serotonin transporter gene in this large Australian cohort; however, the inverse association observed with the 10-copy allele warrants further investigation. Copyright (C) 2000 S. Karger AG, Basel.

Serotonergic mechanisms of the median raphe nucleus-dorsal hippocampus in conditioned fear: Output circuit involves the prefrontal cortex and amygdala

Independent studies have shown that the median raphe nucleus (MRN) and dorsal hippocampus (DH) are involved in the expression of contextual conditioned fear (CFC). However, studies that examine the integrated involvement of serotonergic mechanisms of the MRN-DH are lacking. To address this issue, a CFC paradigm was used to test whether the serotonergic projections from the MRN to DH can influence CFC. Serotoninergic drugs were infused either into the MRN or DH prior to testing sessions in which freezing and startle responses were measured in the same context where 6 h previously rats received footshocks. A reduction of serotonin (5-HT) transmission in the MRN by local infusions of the 5-HT(1A) agonist 8-hydroxy-2-(di-n-propylamino)-tetralin (8-OH-DPAT) decreased freezing in response to the context but did not reduce fear-potentiated startle. This pattern of results is consistent with the hypothesis that MRN serotonergic mechanisms selectively modulate the freezing response to the aversive context. As for the DH, a decrease in postsynaptic 5-HT receptor activity at projection areas has been proposed to be the main consequence of 5-HT(1A) receptor activation in the MIRN. Intra-DH injections of 8-OH-DPAT inhibited both the freezing and fear-potentiated startle response to the context. To reconcile these findings, an inhibitory mechanism may exist between the incoming 5-HT pathway from the MRN to DH and the neurons of the DH output to other structures. The DH-amygdala or medial prefrontal cortex projections could well be this output circuit modulating the expression of CFC as revealed by measurements of Fos immunoreactivity in these areas. (C) 2009 Elsevier B.V. All rights reserved.

Aripiprazole for Patients with Schizophrenia and Schizoaffective Disorder: An Open-Label, Randomized, Study Versus Haloperidol

Introduction: Aripiprazole, a dopamine D(2) receptor partial agonist, has also partial agonist activity at serotonin (5-HT)(1A) receptors and antagonist activity at 5-HT(2A) receptors. Methods: In this 8-week, multicenter, randomized, parallel-group, open-label, flexible-dose study, patients diagnosed with schizophrenia or schizoaffective disorder were randomized to aripiprazole 15-30 mg/day or haloperidol 10-15 mg/day. Results: Patients treated with both aripiprazole and haloperidol improved from baseline in Positive and Negative Syndrome Scale total, positive, and negative scores as well as in Clinical Global Impressions scores (all P<.001). At the end of the study, the percentage of patients classified as responders-according to >= 40% reduction in the Positive and Negative Syndrome Scale negative subscale score-was significantly higher in the aripiprazole group (20%) than in the haloperidol group (0%) (P<.05). Additionally, a higher number of patients receiving haloperidol required more anticholinergic medications (P<.001) than aripiprazole-treated patients, whereas more aripiprazole (45.5%) than haloperidol-treated patients (12.9%) required benzodiazepines (P=.002). At endpoint, rates of preference of medication were higher in the aripiprazole group (63.2%) than in the haloperidol group (21.7%), as expressed by patients and caregivers (P=.001). Conclusion: Aripiprazole and haloperidol had similar efficacy in terms of reduction of overall psychopathology. Although aripiprazole has been demonstrated to be superior concerning negative symptoms and in terms of tolerability (extrapyramidal symptoms) and preferred by patients and caregivers than haloperidol, significantly more aripiprazole-treated patients required benzodiazepines.

Aripiprazole, an atypical antipsychotic prevents the motor hyperactivity induced by psychotomimetics, and psyphostimulants in mice

Aripiprazole is an atypical antipsychotic that acts as a partial agonist at the dopamine D-2 receptor. It has been mainly investigated in dopamine-based models of schizophrenia, while its effects on glutamate-based paradigms have remained to be further characterized. Due to its unique mechanism of action, aripiprazole has also been considered as a replacement medication for psychostimulant abuse. Thus, in the present study we tested the hypothesis that aripiprazole would prevent the motor hyperactivity induced by psychostimulant and psychotomimetic drugs that act either by dopaminergic or glutamatergic mechanisms. Male Swiss mice received injections of aripiprazole (0.1-1 mg/kg) followed by drugs that enhance the dopamine-mediated neurotransmission, amphetamine (3 mg/kg) or cocaine (5 mg/kg), or by glutamate NMDA-receptor antagonists, ketamine (60 mg/kg) or MK-801 (0.4 mg/kg). Independent groups also received aripiprazole (0.1-1 mg/kg) or haloperidol (0.5 mg/kg) and were tested for catalepsy. All doses of aripiprazole were effective in preventing the motor stimulant effects of amphetamine and cocaine. Moreover, the higher dose also prevented the effects of ketamine and MK-801. The present study reports the effects of aripiprazole in dopaminergic and glutamatergic models predictive of antipsychotic activity, suggesting that both may be useful for screening novel partial agonists with antipsychotic activity. It also shows that aripiprazole may prevent the acute effects of psychostimulant drugs without significant motor impairment. C) 2007 Elsevier B.V. All rights reserved.

Involvement of the prelimbic prefrontal cortex on cannabidiol-induced attenuation of contextual conditioned fear in rats

Rationale: Systemic administration of cannabidiol (CBD), a non-psychotomimetic component of Cannabis sativa, is able to attenuate cardiovascular and behavioral (freezing) changes induced by re-exposure to a context that had been previously paired with footshocks. The brain sites mediating this effect, however, remain unknown. The medial prefrontal cortex (mPFC) has been related to contextual fear conditioning. Objectives: (1) To verify, using c-Fos immunocytochemistry, if the mPFC is involved in the attenuation of contextual fear induced by systemic administration of CBD; (2) to investigate if direct microinjections of CBD into mPFC regions would also attenuate contextual fear. Results: Confirming previous results systemic administration of CBD (10 mg/kg) decreased contextual fear and associated c-Fos expression in the prefrontal cortex (prelimbic and infralimbic regions). The drug also attenuated c-Fos expression in the bed nucleus of the stria terminalis (BNST). Direct CBD (30 nmol) microinjection into the PL prefrontal cortex reduced freezing induced by re-exposure to the aversively conditioned context. In the infralimbic (IL) prefrontal cortex, however, CBD (30 nmol) produced an opposite result, increasing the expression of contextual fear conditioning. This result was confirmed by an additional experiment where the conditioning session was performed under a less aversive protocol. Conclusion: These results suggest that the PL prefrontal cortex may be involved in the attenuation of contextual fear induced by systemic injection of CBD. They also support the proposition that the IL and PL play opposite roles in fear conditioning. A possible involvement of the BNST in CBD effects needs to be further investigated. (C) 2009 Elsevier B.V. All rights reserved.

Distinct Effects of Delta 9-Tetrahydrocannabinol and Cannabidiol on Neural Activation During Emotional Processing

Context: Cannabis use can both increase and reduce anxiety in humans. The neurophysiological substrates of these effects are unknown. Objective: To investigate the effects of 2 main psycho-active constituents of Cannabis sativa (Delta 9-tetrahydrocannabinol [Delta 9-THC] and cannabidiol [CBD]) on regional brain function during emotional processing. Design: Subjects were studied on 3 separate occasions using an event-related functional magnetic resonance imaging paradigm while viewing faces that implicitly elicited different levels of anxiety. Each scanning session was preceded by the ingestion of either 10 mg of Delta 9-THC, 600 mg of CBD, or a placebo in a double-blind, randomized, placebo-controlled design. Participants: Fifteen healthy, English-native, right-handed men who had used cannabis 15 times or less in their life. Main Outcome Measures: Regional brain activation (blood oxygenation level-dependent response), electrodermal activity (skin conductance response [SCR]), and objective and subjective ratings of anxiety. Results: Delta 9-Tetrahydrocannabinol increased anxiety, as well as levels of intoxication, sedation, and psychotic symptoms, whereas there was a trend for a reduction in anxiety following administration of CBD. The number of SCR fluctuations during the processing of intensely fearful faces increased following administration of Delta 9-THC but decreased following administration of CBD. Cannabidiol attenuated the blood oxygenation level dependent signal in the amygdala and the anterior and posterior cingulate cortex while subjects were processing intensely fearful faces, and its suppression of the amygdalar and anterior cingulate responses was correlated with the concurrent reduction in SCR fluctuations. Delta 9-Tetrahydrocannabinol mainly modulated activation in frontal and parietal areas. Conclusions: Delta 9-Tetrahydrocannabinol and CBD had clearly distinct effects on the neural, electrodermal, and symptomatic response to fearful faces. The effects of CBD on activation in limbic and paralimbic regions may contribute to its ability to reduce autonomic arousal and subjective anxiety, whereas the anxiogenic effects of Delta 9-THC may be related to effects in other brain regions.

Clinically significant drug interactions with agents specific for migraine attacks

The drugs which provide specific relief from migraine attacks, the ergopeptides (ergotamine and dihydroergotamine) and the various 'triptans' (notably sumatriptan), are often prescribed for persons already taking various migraine preventative agents, and sometimes drugs for other indications. As a result, migraine-specific drugs may become involved in drug-drug interactions. The migraine-specific drugs all act as agonists at certain subclasses of serotonin (5-hydroxytryptamine; 5-MT) receptor, particularly those of the 5-HT1D subtype, and produce vasoconstriction through these receptor-mediated mechanisms. The oral bioavailabilities of these drugs, particularly those of the ergopeptides, are often incomplete, due to extensive presystemic metabolism. As a result, if migraine-specific agents are coadministered with drugs with vasoconstrictive properties, or with drugs which inhibit the metabolism of the migraine-specific agents, there is a risk of interactions occurring which produce manifestations of excessive vasoconstriction. This can also occur through pharmacodynamic mechanisms, as when ergopeptides or triptans are coadministered with methysergide or propranolol (although a pharmacokinetic element may apply in relation to the latter interaction), or if one migraine-specific agent is used shortly after another. When egopeptide metabolism is inhibited by the presence of macrolide antibacterials, particularly troleandomycin and erythromycin, the resultant interaction can produce ergotism, sometimes leading to gangrene. Similar pharmacokinetic mechanisms, with their vasoconstrictive consequences, probably apply to combination of the ergopeptides with HIV protease inhibitors (indinavir and ritonavir), heparin, cyclosporin or tacrolimus. Inhibition of triptan metabolism by monoamine oxidase A inhibitors, e.g. moclobemide, may raise circulating triptan concentrations, although this does not yet seem to have led to reported clinical problems. Caffeine may cause increased plasma ergotamine concentrations through an as yet inadequately defined pharmacokinetic interaction. However, a direct antimigraine effect of caffeine may contribute to the claimed increased efficacy of ergotamine-caffeine combinations in relieving migraine attacks. Serotonin syndromes have been reported as probable pharmacodynamic consequences of the use of ergots or triptans in persons taking serotonin reuptake inhibitors. There have been two reports of involuntary movement disorders when sumatriptan has been used by patients already taking loxapine. Nearly all the clinically important interactions between the ergopeptide antimigraine agents and currently marketed drugs are likely to have already come to notice. In contrast, new interactions involving the triptans are likely to be recognised as additional members of this family of drugs, with their different patterns of metabolism and pharmacokinetics, are marketed.

Pharmacotherapy of intermittent claudication

Intermittent claudication (IC) is leg muscle pain, cramping and fatigue brought on by exercise and is the primary symptom of peripheral arterial disease. The goals of pharmacotherapy for IC are to increase the walking capacity/quality of life and to decrease rates of amputation. In 1988, pentoxifylline was the only drug that had reasonable supportive clinical trial evidence for being beneficial in IC. Since then a number of drugs have shown benefit or potential in IC. Cilostazol, a specific inhibitor of phosphodiesterase 3 and activator of lipoprotein lipase, clearly increases pain-free and absolute walking distances in claudicants. However, cilostazol does cause minor side effects including headache, diarrhoea, loose stools and flatulence. Naftidrofuryl, a serotonin (5-HT2) receptor antagonist and antiplatelet drug, is beneficial in claudicants. Inhibitors of platelet aggregation (including nitric oxide from L-arginine or glyceryl trinitrate) and anticoagulants (low molecular weight heparin, defibrotide) probably have both short and long-term benefits in IC. In addition, intravenous infusions of prostaglandins (PGs) PGE1 and PGI2 have an established role in severe peripheral arterial disease and the recent introduction of longer lasting and/or oral forms of the PGs makes them more likely to be useful in the IC associated with less severe forms of the disease. There are some exciting new approaches to the treatment of IC, including propionyl-L-carnitine and basic fibroblast growth factor (bFGF).

BDNF overexpression in mouse hippocampal astrocytes promotes local neurogenesis and elicits anxiolytic-like activities.

The therapeutic activity of selective serotonin (5-HT) reuptake inhibitors (SSRIs) relies on long-term adaptation at pre- and post-synaptic levels. The sustained administration of SSRIs increases the serotonergic neurotransmission in response to a functional desensitization of the inhibitory 5-HT1A autoreceptor in the dorsal raphe. At nerve terminal such as the hippocampus, the enhancement of 5-HT availability increases brain-derived neurotrophic factor (BDNF) synthesis and signaling, a major event in the stimulation of adult neurogenesis. In physiological conditions, BDNF would be expressed at functionally relevant levels in neurons. However, the recent observation that SSRIs upregulate BDNF mRNA in primary cultures of astrocytes strongly suggest that the therapeutic activity of antidepressant drugs might result from an increase in BDNF synthesis in this cell type. In this study, by overexpressing BDNF in astrocytes, we balanced the ratio between astrocytic and neuronal BDNF raising the possibility that such manipulation could positively reverberate on anxiolytic-/antidepressant-like activities in transfected mice. Our results indicate that BDNF overexpression in hippocampal astrocytes produced anxiolytic-/antidepressant-like activity in the novelty suppressed feeding in relation with the stimulation of hippocampal neurogenesis whereas it did not potentiate the effects of the SSRI fluoxetine on these parameters. Moreover, overexpressing BDNF revealed the anxiolytic-like activity of fluoxetine in the elevated plus maze while attenuating 5-HT neurotransmission in response to a blunted downregulation of the 5-HT1A autoreceptor. These results emphasize an original role of hippocampal astrocytes in the synthesis of BDNF, which can act through neurogenesis-dependent and -independent mechanisms to regulate different facets of anxiolytic-like responses.

Upregulation of vasopressin V1A receptor mRNA and protein in vascular smooth muscle cells following cyclosporin A treatment.

1. The major side effects of the immunosuppressive drug cyclosporin A (CsA) are hypertension and nephrotoxicity. It is likely that both are caused by local vasoconstriction. 2. We have shown previously that 20 h treatment of rat vascular smooth muscle cells (VSMC) with therapeutically relevant CsA concentrations increased the cellular response to [Arg8]vasopressin (AVP) by increasing about 2 fold the number of vasopressin receptors. 3. Displacement experiments using a specific antagonist of the vasopressin V1A receptor (V1AR) showed that the vasopressin binding sites present in VSMC were exclusively receptors of the V1A subtype. 4. Receptor internalization studies revealed that CsA (10(-6) M) did not significantly alter AVP receptor trafficking. 5. V1AR mRNA was increased by CsA, as measured by quantitative polymerase chain reaction. Time-course studies indicated that the increase in mRNA preceded cell surface expression of the receptor, as measured by hormone binding. 6. A direct effect of CsA on the V1AR promoter was investigated using VSMC transfected with a V1AR promoter-luciferase reporter construct. Surprisingly, CsA did not increase, but rather slightly reduced V1AR promoter activity. This effect was independent of the cyclophilin-calcineurin pathway. 7. Measurement of V1AR mRNA decay in the presence of the transcription inhibitor actinomycin D revealed that CsA increased the half-life of V1AR mRNA about 2 fold. 8. In conclusion, CsA increased the response of VSMC to AVP by upregulating V1AR expression through stabilization of its mRNA. This could be a key mechanism in enhanced vascular responsiveness induced by CsA, causing both hypertension and, via renal vasoconstriction, reduced glomerular filtration.

Depression-like behavior is dependent on age in male SAMP8 mice

Aging is associated with an increased risk of depression in humans. To elucidate the underlying mechanisms of depression and its dependence on aging, here we study signs of depression in male SAMP8 mice. For this purpose, we used the forced swimming test (FST). The total floating time in the FST was greater in SAMP8 than in SAMR1 mice at 9 months of age; however, this difference was not observed in 12-month-old mice, when both strains are considered elderly. Of the two strains, only the SAMP8 animals responded to imipramine treatment. We also applied the dexamethasone suppression test (DST) and studied changes in the dopamine and serotonin (5-HT) uptake systems, the 5-HT2a/2c receptor density in the cortex, and levels of TPH2. The DST showed a significant difference between SAMR1 and SAMP8 mice at old age. SAMP8 exhibits an increase in 5-HT transporter density, with slight changes in 5-HT2a/2c receptor density. In conclusion, SAMP8 mice presented depression-like behavior that is dependent on senescence process, because it differs from SAMR1, senescence resistant strain.

Depression-like behavior is dependent on age in male SAMP8 mice

Aging is associated with an increased risk of depression in humans. To elucidate the underlying mechanisms of depression and its dependence on aging, here we study signs of depression in male SAMP8 mice. For this purpose, we used the forced swimming test (FST). The total floating time in the FST was greater in SAMP8 than in SAMR1 mice at 9 months of age; however, this difference was not observed in 12-month-old mice, when both strains are considered elderly. Of the two strains, only the SAMP8 animals responded to imipramine treatment. We also applied the dexamethasone suppression test (DST) and studied changes in the dopamine and serotonin (5-HT) uptake systems, the 5-HT2a/2c receptor density in the cortex, and levels of TPH2. The DST showed a significant difference between SAMR1 and SAMP8 mice at old age. SAMP8 exhibits an increase in 5-HT transporter density, with slight changes in 5-HT2a/2c receptor density. In conclusion, SAMP8 mice presented depression-like behavior that is dependent on senescence process, because it differs from SAMR1, senescence resistant strain.