Combined Treatment with Citalopram and Buspirone: Effects on Serotonin 5-HT2Aand 5-HT2CReceptors in the Rat Brain

Aripiprazole Offsets Mutant ATXN3-Induced Motor Dysfunction by Targeting Dopamine D2 and Serotonin 1A and 2A Receptors in C. elegans

The atypical antipsychotic aripiprazole is a Food and Drug Administration-approved drug for the treatment of psychotic, mood, and other psychiatric disorders. Previous drug discovery efforts pinpointed aripiprazole as an effective suppressor of Machado–Joseph disease (MJD) pathogenesis, as its administration resulted in a reduced abundance and aggregation of mutant Ataxin-3 (ATXN3) proteins. Dopamine partial agonism and functional selectivity have been proposed as the main pharmacological mechanism of action of aripiprazole in the treatment of psychosis; however, this mechanism remains to be determined in the context of MJD. Here, we focus on confirming the efficacy of aripiprazole to reduce motor dysfunction in vivo, using a Caenorhabditis elegans (C. elegans) model of MJD, and on unveiling the drug targets required for its positive action against mutant ATXN3 pathogenesis. We employed pharmacogenetics and pharmacological approaches to identify which dopamine and serotonin receptors are critical for aripiprazole-mediated improvements in motor function. We demonstrated that dopamine D₂-like and serotonin 5-HT_1A and 5-HT_2A receptors play important roles in this process. Our findings strengthen the relevance of dopaminergic and serotoninergic signaling modulation against mutant ATXN3-mediated pathogenesis. The identification of aripiprazole’s cellular targets, relevant for MJD and perhaps other neurodegenerative diseases, may pave the way for prospective drug discovery and development campaigns aiming to improve the features of this prototypical compound and reduce side effects not negligible in the case of aripiprazole.

Adaptive mechanisms following antidepressant drugs: Focus on serotonin 5-HT2A receptors

BACKGROUND

There is a strong support for the role of serotonin (5-HT) neurotransmission in depression and in the mechanism of action of antidepressants. Among 5-HT receptors, 5-HT2A receptor subtype seems to be an important target implicated in the above disorder.

METHODS

The aim of the study was to investigate the effects of antidepressants, such as imipramine (15 mg/kg), escitalopram (10 mg/kg) and tianeptine (10 mg/kg) as well as drugs with antidepressant activity, including N-acetylcysteine (100 mg/kg) and URB597 (a fatty acid amide hydrolase inhibitor, 0.3 mg/kg) on the 5-HT2A receptor labeling pattern in selected rat brain regions. Following acute or chronic (14 days) drug administration, rat brains were analyzed by using autoradiography with the 5-HT2A receptor antagonist [3H]ketanserin.

RESULTS

Single dose or chronic administration of imipramine decreased the radioligand binding in the claustrum and cortical subregions. The [3H]ketanserin binding either increased or decreased in cortical areas after acute N-acetylcysteine and URB597 administration, respectively. A similar shift towards reduction of the [3H]ketanserin binding was detected in the nucleus accumbens shell following either acute treatment with imipramine, escitalopram, N-acetylcysteine and URB597 or repeated administration of imipramine, tianeptine and URB597.

CONCLUSIONS

In conclusion, the present result indicate different sensitivity of brain 5-HT2A receptors to antidepressant drugs depending on schedule of drug administration and rat brain regions. The decrease of accumbal shell 5-HT2A receptor labeling by antidepressant drugs exhibiting different primary mechanism of action seems to be a common targeting mechanism associated with the outcome of depression treatment.

Fluoxetine-Induced Sleep Bruxism Rapidly Treated With Once-Nightly Dosing of Buspirone in a 6-Year-Old Girl

Fluoxetine is a selective serotonin reuptake inhibitor that is commonly used in children and adolescents. Several reports exist regarding the relationship of fluoxetine use and sleep bruxism. We report the case of a 6-year-old girl who was successfully treated with once-nightly dosing of buspirone for fluoxetine-induced sleep bruxism, which was confirmed with clear on-off-on treatment sequence.

Discovering the mechanisms underlying serotonin (5-HT)2A and 5-HT2C receptor regulation following nicotine withdrawal in rats

We have previously demonstrated that nicotine withdrawal produces depression-like behavior and that serotonin (5-HT)2A/2C receptor ligands modulate that mood-like state. In the present study we aimed to identify the mechanisms (changes in radioligand binding, transcription or RNA-editing) related to such a behavioral outcome. Rats received vehicle or nicotine (0.4 mg/kg, s.c.) for 5 days in home cages. Brain 5-HT2A/2C receptors were analyzed on day 3 of nicotine withdrawal. Nicotine withdrawal increased [(3)H]ketanserin binding to 5-HT2A receptors in the ventral tegmental area and ventral dentate gyrus, yet decreased binding in the nucleus accumbens shell. Reduction in [(3)H]mesulergine binding to 5-HT2C receptors was seen in the ventral dentate gyrus. Profound decrease in the 5-HT2A receptor transcript level was noted in the hippocampus and ventral tegmental area. Out of five 5-HT2C receptor mRNA editing sites, deep sequencing data showed a reduction in editing at the E site and a trend toward reduction at the C site in the hippocampus. In the ventral tegmental area, a reduction for the frequency of CD 5-HT2C receptor transcript was seen. These results show that the reduction in the 5-HT2A receptor transcript level may be an auto-regulatory response to the increased receptor density in the hippocampus and ventral tegmental area during nicotine withdrawal, while decreased 5-HT2C receptor mRNA editing may explain the reduction in receptor labeling in the hippocampus. Serotonin (5-HT)2A/2C receptor ligands alleviate depression-like state in nicotine-withdrawn rats. Here, we show that the reduction in 5-HT2A receptor transcript level may be an auto-regulatory response to the increased receptor number in the hippocampus and ventral tegmental area during nicotine withdrawal, while attenuated 5-HT2C receptor mRNA editing in the hippocampus might explain reduced inverse agonist binding to 5-HT2C receptor and suggest a shift toward a population of more active receptors. 5-HT, serotonin; 5-HT2A R, 5-HT2A receptor; 5-HT2C R, 5-HT2C receptor.

Yokukansan, a traditional Japanese medicine, decreases head-twitch behaviors and serotonin 2A receptors in the prefrontal cortex of isolation-stressed mice

ETHNOPHARMACOLOGICAL RELEVANCE

Yokukansan, a traditional Japanese (Kampo) medicine, has recently been used to treat the behavioral and psychological symptoms of dementia (BPSD), including aggressiveness, excitability, and hallucination. The present study was designed to investigate the mechanisms underlying the ameliorative effects of yokukansan on BPSD using animals exhibiting hallucination-like behaviors. For this purpose, we initially examined whether chronic isolation stress increases the frequency of hallucination in response to a psychedelic drug. Using this animal model, we next examined the effects of yokukansan on drug-induced hallucination-like behaviors. Finally, we examined the density and mRNA levels of serotonin 2A (5-HT2A) receptors.

MATERIALS AND METHODS

Male mice were subjected to isolation stress for six weeks. Yokukansan was incorporated into food pellets, and administered to the mice for six weeks. In some experiments, yokukansan and each of seven constituent herbs were administered orally to the mice for the last two weeks during the six-week period of isolation stress. A 5-HT2A receptor agonist, 2,5-dimethoxy-4-iodoamphetamine (DOI, 2.5mg/kg), was injected into the mice, and head-twitch behaviors were quantified. The binding sites of 5-HT2A receptors on the plasma membrane of the prefrontal cortex (PFC) were assessed by a receptor-binding assay using tritium-labeled ketanserin, and the density and affinity were calculated from a Scatchard plot. The level of mRNAs was measured by PCR analyses.

RESULTS

Isolation stress enhanced the frequency of the DOI-induced head-twitch response, and yokukansan treatment by feeding significantly reduced this enhancement. Isolation stress significantly increased the 5-HT2A receptor density in the PFC, and yokukansan treatment by feeding as well as administration significantly down-regulated this increase. Isolation stress and yokukansan did not affect the affinity. Among seven constituent herbs, Bupleurum Root, Uncaria Hook, Japanese Angelica Root, and Glycyrrhiza down-regulated the increase, but statistically not significant, in which their efficacies were over 50% relative to yokukansan. Neither isolation stress nor yokukansan affected mRNA levels of 5-HT2A receptors.

CONCLUSION

Yokukansan attenuated drug-induced hallucination-like behaviors in isolated mice, which is suggested to be mediated by 5-HT2A receptor down-regulation in the PFC. This mechanism may underlie the ameliorative effects of yokukansan on hallucination.

Context-controlled nicotine-induced changes in the labeling of serotonin (5-HT)2A and 5-HT2C receptors in the rat brain

BACKGROUND

We have previously demonstrated that serotonin (5-HT)2A and 5-HT2C receptor ligands modulate the sensitizing effects of nicotine. In the present study we used male rats to verify the hypothesis that the binding pattern of 5-HT2A and 5-HT2C receptors in the brain is altered by chronic nicotine treatment in different environments.

METHODS

Rats were given repeatedly vehicle or nicotine in different sensitizing regimens (home or experimental cages). On day 10, animals were challenged with nicotine (expression of nicotine sensitization) or vehicle in either home or experimental cages, and were sacrificed immediately after the experiment.

RESULTS

Repeated treatment with nicotine in home cages evoked significant increases in [(3)H]ketanserin binding to 5-HT2A receptors in the prefrontal cortex, striatal subregions and ventral tegmental area as well as reductions in [(3)H]mesulergine binding to 5-HT2C receptors in subregions of the prefrontal cortex. In contrast, nicotine paired with environmental context produced robust increases in 5-HT2A receptor labeling in the infralimbic cortex and decreased [(3)H]ketanserin binding in striatal subregions and ventral tegmental area; 5-HT2C receptor labeling in the prefrontal cortex fell.

CONCLUSIONS

The present data indicate that chronic nicotine administration in home cages induces bi-directional neuroplastic changes within 5-HT2A and 5-HT2C receptors in the prefrontal cortex. Pairing the nicotine with environmental context potentiates the neuroplastic response in the latter region and evokes opposite changes in 5-HT2A receptor binding in striatal and tegmental regions compared with nicotine administered in the absence of the context, indicating a modulatory role of environmental context in the expression of nicotine-induced sensitization.

Randomized, single-blind, trial of sertraline and buspirone for treatment of elderly patients with generalized anxiety disorder

AIM

Generalized anxiety disorder (GAD) in elderly people is common, but few systematic studies regarding the best treatments have been performed. The aim of the present study was to evaluate the efficacy and safety of sertraline and buspirone in the treatment of elderly patients with GAD.

METHODS

Based on selection criteria, 46 patients were recruited who met DSM-IV criteria for GAD. Patients were randomly assigned to sertraline (50-100 mg/day) or buspirone (10-15 mg/day) for 8 weeks in a single-blind trial. The primary outcome measure used in the present study was the Hamilton Rating Scale for Anxiety (HRSA).

RESULTS

Both sertraline and buspirone had significant anxiolytic efficacy. A steady decrease in the total HRSA scores for both groups was observed throughout the study period. After 2 and 4 weeks, buspirone was found to be significantly superior to sertraline (P < 0.001), but at the end of study period this difference did not reach statistical significance (P = 0.16). The mean HRSA score after 8 weeks significantly decreased in subjects treated with sertraline (P < 0.001), and buspirone (P < 0.001). No clinically adverse events or changes in laboratory test results were observed during the study period.

CONCLUSION

Both sertraline and buspirone appear to be efficacious and well tolerated in the treatment of GAD in elderly patients. Further studies with larger sample size, evaluating the effect of medical illness, cognitive impairment, depression, and combined therapy with support and psychotherapy are needed.