The 5-HT2 antagonist ritanserin blocks dopamine re-uptake in the rat frontal cortex

Congenital aniridia beyond black eyes: From phenotype and novel genetic mechanisms to innovative therapeutic approaches

Congenital PAX6-aniridia, initially characterized by the absence of the iris, has progressively been shown to be associated with other developmental ocular abnormalities and systemic features making congenital aniridia a complex syndromic disorder rather than a simple isolated disease of the iris. Moreover, foveal hypoplasia is now recognized as a more frequent feature than complete iris hypoplasia and a major visual prognosis determinant, reversing the classical clinical picture of this disease. Conversely, iris malformation is also a feature of various anterior segment dysgenesis disorders caused by PAX6-related developmental genes, adding a level of genetic complexity for accurate molecular diagnosis of aniridia. Therefore, the clinical recognition and differential genetic diagnosis of PAX6-related aniridia has been revealed to be much more challenging than initially thought, and still remains under-investigated. Here, we update specific clinical features of aniridia, with emphasis on their genotype correlations, as well as provide new knowledge regarding the PAX6 gene and its mutational spectrum, and highlight the beneficial utility of clinically implementing targeted Next-Generation Sequencing combined with Whole-Genome Sequencing to increase the genetic diagnostic yield of aniridia. We also present new molecular mechanisms underlying aniridia and aniridia-like phenotypes. Finally, we discuss the appropriate medical and surgical management of aniridic eyes, as well as innovative therapeutic options. Altogether, these combined clinical-genetic approaches will help to accelerate time to diagnosis, provide better determination of the disease prognosis and management, and confirm eligibility for future clinical trials or genetic-specific therapies.

Synthesis, Crystal Structure, and Biological Evaluation of Fused Thiazolo[3,2-a]Pyrimidines as New Acetylcholinesterase Inhibitors

A new series of thiazolo[3,2-a]pyrimidine bromide salt derivatives 7a–d were synthesized from 3,4-dihydropyrimidinethione precursors. The target compounds were fully characterized by 1D- and 2D-NMR, high resolution ESI-MS/MS and single crystal X-ray diffraction analysis, which confirmed a regioselective 5H cyclization of the dihydropyrimidinethiones. All target compounds were evaluated in vitro as human acetylcholinesterase (hAChE) inhibitors via an Ellman-based colorimetric assay and showed good inhibition activities (better than 70% at 10 µM and IC₅₀ values in the 1 µM range). Molecular docking simulations for all target products into hAChE were performed and confirmed strong binding to the enzyme. These results provide a promising and new starting point to improve acetylcholinesterase inhibitors and explore novel treatment options against Alzheimer’s disease.

One-pot synthesis, biological evaluation and molecular docking studies of fused thiazolo[2,3-b]pyrimidinone-pyrazolylcoumarin hybrids

As a part of our endeavor toward the synthesis of a new class of biologically potent heterocyclic hybrids, a series of newly fused thiazolo[2,3-b]pyrimidinones bearing a pyrazolylcoumarin moiety (6a-p) were synthesized in acceptable yields. Anticipated structures of all titled compounds were in agreement with spectral and analytical (C, H and N) analyses. The compounds were screened for in vitro antibacterial activity against both G⁺ and G^- bacterial strains and antiproliferative activity against K562 (chronic myelogenous leukemia), MCF-7 (breast cancer), MDA-MB-231 (breast cancer), COLO 205 (colorectal adenocarcinoma), HepG2 (hepatocellular carcinoma) cell lines. Further, potent antibacterial compounds were subjected to molecular docking studies in order to gain insight into their plausible binding modes and mechanism of action against MurB. The modeling results were in agreement with the experimental data.

Antidepressant-like effect of extract from Polygala paniculata: involvement of the monoaminergic systems

CONTEXT

Polygala paniculata Linnaeus (Polygalaceae) has shown neuroprotective effects, but there is no report about its antidepressant potential.

OBJECTIVE

The antidepressant-like effect of the hydroalcoholic extract from P. paniculata and some of the possible mechanisms involved in this effect were investigated in forced swimming test (FST).

MATERIALS AND METHODS

Mice received extract by oral route and were submitted to FST and open-field test. Animals were forced to swim and the total immobility time was registered (6-min period). A reduction in the immobility time is considered an antidepressant-like effect. In order to investigate the involvement of the monoaminergic systems, mice were treated with pharmacological antagonists before administration of the extract.

RESULTS

The acute administration of the hydroalcoholic extract from P. paniculata produced an antidepressant-like effect, since it significantly reduced the immobility time in FST (0.01-30 mg/kg) as compared to control group, without changing locomotor activity. Pretreatment of mice with yohimbine (1 mg/kg, i.p., α₂-adrenoceptor antagonist), propranolol (1 mg/kg, i.p., β-adrenoceptor antagonist), SCH23390 (0.05 mg/kg, s.c., dopamine D₁ receptor antagonist) or sulpiride (50 mg/kg, i.p., dopamine D₂ receptor antagonist) prevented the antidepressant-like effect of the extract in FST (30 mg/kg). Moreover, ketanserin (5 mg/kg, i.p., preferential 5-HT(2A) receptor antagonist) enhanced the effect of the extract in FST.

DISCUSSION AND CONCLUSION

The results of the present study indicate that the extract from P. paniculata has an antidepressant-like action that is likely mediated by an interaction with the serotonergic (5-HT2A receptors), noradrenergic (α₂ and β-receptor) and dopaminergic (D₁ and D₂ receptors) systems.

Serotonergic mechanism underlying tranylcypromine enhancement of nicotine self-administration

Although nicotine is generally considered to be the main psychoactive component of tobacco, growing evidence highlights the importance of nonnicotine compounds in smoking reinforcement. Monoamine oxidase (MAO) inhibition is a major consequence of smoking and MAO inhibitors, such as tranylcypromine, increase nicotine reinforcement. Tranylcypromine has multiple pharmacological effects, increasing monoamine release for a few hours immediately after its administration and blocking MAO activity for several days. To assess the relative role of these two actions, adult male rats were tested in consecutive daily 3-h sessions for self-administration of nicotine (3 μg kg⁻¹) inj⁻¹, i.v.) either 20 or 1 h following administration of tranylcypromine (3 mg kg⁻¹). Both paradigms were shown to produce highly significant inhibition of MAO activity. However, whereas animals readily acquired self-administration when pretreated with tranylcypromine 1 h prior to testing, they did not with the longer pretreatment interval. Such animals did immediately acquire nicotine self-administration when the tranylcypromine pretreatment interval was switched to 1 h prior to testing on Day 4, indicating that an acute effect of the MAO inhibitor was responsible for enhanced nicotine reinforcement. Several lines of evidence implicate serotonin (5-HT) as the mediator of this enhancement: (1) Tranyclypromine-enhanced nicotine reinforcement was blocked by the 5-HT₂ receptor antagonists, ritanserin and ketanserin; (2) parachloroamphetamine (PCA), a 5-HT releaser, also enhanced nicotine self-administration in animals in which MAO activity was inhibited; (3) pretreatment with tranylcypromine increased PCA-induced 5-HT overflow in the nucleus accumbens. These findings suggest that MAO inhibition enhances serotonergic transmission, which serves a critical role in the reinforcing effects of nicotine.

Efficacy of antidepressants in treating the negative symptoms of chronic schizophrenia: meta-analysis

BACKGROUND

Treatment of negative symptoms in chronic schizophrenia continues to be a major clinical issue.

AIMS

To analyse the efficacy of add-on antidepressants for the treatment of negative symptoms of chronic schizophrenia.

METHOD

Systematic review and meta-analysis of randomised controlled trials comparing the effect of antidepressants and placebo on the negative symptoms of chronic schizophrenia, measured through standardised rating scales. Outcome was measured as standardised mean difference between end-of-trial and baseline scores of negative symptoms.

RESULTS

There were 23 trials from 22 publications (n = 819). The antidepressants involved were selective serotonin reuptake inhibitors, mirtazapine, reboxetine, mianserin, trazodone and ritanserin; trials on other antidepressants were not available. The overall standardised mean difference was moderate (-0.48) in favour of antidepressants and subgroup analysis revealed significant responses for fluoxetine, trazodone and ritanserin.

CONCLUSIONS

Antidepressants along with antipsychotics are more effective in treating the negative symptoms of schizophrenia than antipsychotics alone.

Effects of clozapine on behavioral sensitization induced by cocaine

Using cocaine-sensitized mice as a model for psychosis, this study investigated whether subchronic treatment with clozapine could affect the sensitized state of the animals and examined the accompanying molecular changes in the brain. To induce sensitization, ICR mice (n=44) were treated with cocaine for 5 days. After 7 days of withdrawal, sensitization was confirmed by a cocaine challenge. Then, the sensitized animals were treated with clozapine for 5 days and rechallenged with cocaine. The frontal cortices were removed from the mice (n=16) 24 h after the last challenge, and the phosphorylation status of some key signaling molecules was investigated. Compared with the sensitized mice receiving the vehicle treatment, the sensitized mice receiving subchronic clozapine showed less locomotor activity, with an activity level similar to that of non-sensitized mice. However, clozapine did not directly affect the stimulatory effect of cocaine. Clozapine also reversed some of the sensitization-induced biochemical changes, including increased phosphorylation of GSK-3beta and CREB, in the frontal cortex. Subchronic treatment with clozapine apparently de-sensitized the sensitized mice. The long-term effect of clozapine on stimulant-induced sensitization may be related to the therapeutic effect of the drug as an antipsychotic agent.

Nicotinic-serotonergic drug interactions and attentional performance in rats

RATIONALE

Both central serotonergic and nicotinic systems play important roles in a variety of neurobehavioral functions; however, the interactions of these two systems have not been fully characterized. The current study served to determine the impact of a relatively selective 5-HT2A receptor antagonist, ketanserin, on attentional function in rats and the interactions of ketanserin with nicotine administration.

METHODS

A standard operant visual signal detection task was used to assess sustained attention. In expt 1, adult female Sprague-Dawley rats (n = 39) were injected subcutaneously (SC) with a dose range of ketanserin (0, 0.25, 0.5 and 1 mg/kg). In expt 2, the interactions of acute ketanserin (0, 1 and 2 mg/kg, SC) and acute nicotine (0, 25 and 50 microg/kg, SC) were assessed. In expt 3, the interaction of acute ketanserin (0, 1 and 2 mg/kg, SC) and chronic nicotine (5 mg/kg per day, SC for 4 weeks via osmotic pump) was characterized. Using an operant visual signal detection task, three possible outcomes (dependent variables) were measured in each trial: percent hit, percent correct rejection, and response omissions.

RESULTS

Ketanserin, when given alone, did not have a significant effect on either percent hit or percent correct rejection. Acute administration of 25 microg/kg nicotine significantly improved percent hit (i.e. improvement in choice accuracy), an effect that was reversed by acute administration of 1 mg/kg ketanserin. Chronic nicotine infusion for 28 consecutive days significantly increased percent correct rejection (i.e. improvement in choice accuracy) without development of tolerance, an effect which was reversed by an acute dose of 2 mg/kg ketanserin.

CONCLUSIONS

These data suggest a functional interaction between nicotine and 5-HT2A receptor antagonist ketanserin.

Ritanserin counteracts both rat vacuous chewing movements and nigro-striatal tyrosine hydroxylase-immunostaining alterations induced by haloperidol

The effect of subchronic co-administration of ritanserin (1.5 mg/kg, i.p., twice a day) and haloperidol (1 mg/kg, i.p., twice a day) on rat vacuous chewing movements and on tyrosine hydroxylase-immunostaining was investigated. Ritanserin significantly reduced rat vacuous chewing movements observed following 2, 3 and 4 weeks of haloperidol administration and after 5 days of haloperidol withdrawal. Furthermore, ritanserin prevented the reduction of striatal tyrosine hydroxylase-immunostaining and the shrinkage of nigral dopaminergic cell bodies induced by haloperidol. The present results indicate that ritanserin may possess protective properties on both dopaminergic nigro-striatal neuron alterations and vacuous chewing movements induced by haloperidol, and provide further evidence indicating a possible association between these two haloperidol-induced effects.