Effects of repeated treatment with the dopamine D2/D3 receptor partial agonist aripiprazole on striatal D2/D3 receptor availability in monkeys

Is aripiprazole a key to unlock anorexia nervosa?: A case series

Aripiprazole contributes an increase in body mass index and attenuation in anorexia nervosa (AN) symptoms, leading clinical improvements with lower side-effect profile; but it is not enough to cure comorbid depressive symptoms in AN.

The partial dopamine D2 receptor agonist aripiprazole is associated with weight gain in adolescent anorexia nervosa

OBJECTIVE

Finding medication to support treatment of anorexia nervosa has been difficult. Neuroscience-based approaches may help in this effort. Recent brain imaging studies in adults and adolescents with anorexia nervosa suggest that dopamine-related reward circuits are hypersensitive and could provide a treatment target.

METHODS

Here, we present a retrospective chart review of 106 adolescents with anorexia nervosa some of whom were treated with the dopamine D2 receptor partial agonist aripiprazole during treatment in a specialized eating disorder program.

RESULTS

The results show that aripiprazole treatment was associated with greater increase in body mass index (BMI) during treatment.

DISCUSSION

The use of dopamine receptor agonists may support treatment success in anorexia nervosa and should be further investigated.

Multi-Atlas Library for Eliminating Normalization Failures in Non-Human Primates

Current tools for automated skull stripping, normalization, and segmentation of non-human primate (NHP) brain MRI studies typically demonstrate high failure rates. Many of these failures are due to a poor initial estimate for the affine component of the transformation. The purpose of this study is to introduce a multi-atlas approach to overcome these limitations and drive the failure rate to near zero. A library of study-specific templates (SST) spanning three Old World primate species (Macaca fascicularis, M. mulatta, Chlorocebus aethiops) was created using a previously described unbiased automated approach. Several modifications were introduced to the methodology to improve initial affine estimation at the study-specific template level, and at the individual subject level. These involve performing multiple separate normalizations to a multi-atlas library of templates and selecting the best performing template on the basis of a covariance similarity metric. This template was then used as an initialization for the affine component of subsequent skull stripping and normalization procedures. Normalization failure rate for SST generation and individual-subject segmentation on a set of 150 NHP was evaluated on the basis of visual inspection. The previous automated template creation procedure results in excellent skull stripping, segmentation, and atlas labeling across species. Failure rate at the individual-subject level was approximately 1%, however at the SST generation level it was 17%. Using the new multi-atlas approach, failure rate was further reduced to zero for both SST generation and individual subject processing. We describe a multi-atlas library registration approach for driving normalization failures in NHP to zero. It is straightforward to implement, and can have application to a wide variety of existing tools, as well as in difficult populations including neonates and the elderly. This approach is also an important step towards developing fully automated high-throughput processing pipelines that are critical for future high volume multi-center NHP imaging studies for studies of drug abuse and brain health.

Targeting the dopamine D3 receptor: an overview of drug design strategies

INTRODUCTION

Dopamine is a neurotransmitter widely distributed in both the periphery and the central nervous system (CNS). Its physiological effects are mediated by five closely related G protein-coupled receptors (GPCRs) that are divided into two major subclasses: the D1-like (D1, D5) and the D2-like (D2, D3, D4) receptors. D3 receptors (D3Rs) have the highest density in the limbic areas of the brain, which are associated with cognitive and emotional functions. These receptors are therefore attractive targets for therapeutic management.

AREAS COVERED

This review summarizes the functional and pharmacological characteristics of D3Rs, including the design and clinical relevance of full agonists, partial agonists and antagonists, as well as the capacity of these receptors to form active homodimers, heterodimers or higher order receptor complexes as pharmacological targets in several neurological and neurodegenerative disorders.

EXPERT OPINION

The high sequence homology between D3R and the D2-type challenges the development of D3R-selective compounds. The design of new D3R-preferential ligands with improved physicochemical properties should provide a better pharmacokinetic/bioavailability profile and lesser toxicity than is found with existing D3R ligands. It is also essential to optimize D3R affinity and, especially, D3R vs. D2-type binding and functional selectivity ratios. Developing allosteric and bitopic ligands should help to improve the D3R selectivity of these drugs. As most evidence points to the ability of GPCRs to form homomers and heteromers, the most promising therapeutic strategy in the future is likely to involve the application of heteromer-selective drugs. These selective ligands would display different affinities for a given receptor depending on the receptor partners within the heteromer. Therefore, designing novel compounds that specifically target and modulate D1R-D3R heteromers would be an interesting approach for the treatment of levodopa (L-DOPA)-induced dyskinesias.

Identifying Medication Targets for Psychostimulant Addiction: Unraveling the Dopamine D3 Receptor Hypothesis

The dopamine D3 receptor (D3R) is a target for developing medications to treat substance use disorders. D3R-selective compounds with high affinity and varying efficacies have been discovered, providing critical research tools for cell-based studies that have been translated to in vivo models of drug abuse. D3R antagonists and partial agonists have shown especially promising results in rodent models of relapse-like behavior, including stress-, drug-, and cue-induced reinstatement of drug seeking. However, to date, translation to human studies has been limited. Herein, we present an overview and illustrate some of the pitfalls and challenges of developing novel D3R-selective compounds toward clinical utility, especially for treatment of cocaine abuse. Future research and development of D3R-selective antagonists and partial agonists for substance abuse remains critically important but will also require further evaluation and development of translational animal models to determine the best time in the addiction cycle to target D3Rs for optimal therapeutic efficacy.