Molecular basis of atypicality of bupropion inferred from its receptor engagement in nervous system tissues

Is there a therapeutic potential in combining bupropion and naltrexone in schizophrenia?

INTRODUCTION

A sustained-release tablet composed of a combination of the dopamine and norepinephrine reuptake inhibitor bupropion (BUP) and the µ-opioid receptor antagonist naltrexone (NAT) is marketed under the brand name Contrave by Orexigen Therapeutics for appetite control. Minimal literature is available regarding the use of combination bupropion and naltrexone (BUPNAT) in individuals with schizophrenia.

AREAS COVERED

In this review, we propose a theoretical model where BUPNAT may have a therapeutic effect in the treatment of schizophrenia. We explore the pathways targeted by the constituent drugs BUP and NAT and summarize the literature on their efficacy and possible adverse effects. We then look at the potential use of BUPNAT in schizophrenia.

EXPERT OPINION

Research has hinted that BUP's dopaminergic properties affect the same striatal pathways involved in schizophrenia. NAT, via opioid receptor antagonism, indirectly increases striatal dopamine release by disinhibiting nicotinic acetylcholine receptors. As such, we hypothesize that BUPNAT can have a therapeutic effect in schizophrenia, particularly on negative symptoms. We also suggest that it may ameliorate comorbidities frequently seen in this group of patients, including obesity, smoking, and substance use. Further research and clinical data are needed to elucidate the potential clinical benefits of BUPNAT in the treatment of schizophrenia.

Comorbidity of Pain and Depression in a Lumbar Disc Herniation Model: Biochemical Alterations and the Effects of Fluoxetine

Summary of Background Data: Depression is one of the most common comorbidities in patients with chronic low back pain. However, the mechanisms of depression in chronic low back pain patients and the effect of antidepressants on the comorbidity of pain and depression need to be further explored. The establishment of the appropriate animal models and of more effective therapies is critical for this comorbidity. Lumbar disc herniation (LDH) is the most common disease that causes low back pain. The current study examined whether an LDH model shows behavioral and biochemical alterations that are in accordance with the characteristics of the comorbidity of pain and depression and tested the effect of fluoxetine (FLX) on these measures.

Objective: The current study examined whether an LDH model showed the behavioral and biochemical alterations that were in accordance with the characteristics of the comorbidity of pain and depression and tested the effect of FLX on these measures.

Methods: The LDH animal model was generated by the implantation of the autologous nucleus pulposus on the left L5 nerve root just proximal to the dorsal root ganglion in Wistar rats. Pain intensity was evaluated by mechanical allodynia and thermal hyperalgesia, and changes in depressive behavior were examined by the taste preference and forced swim tests. Hippocampal serotonin (5-HT) levels were measured by liquid chromatography-mass spectrometry, and tumor necrosis factor-α (TNF-α) mRNA was quantified using real-time reverse transcriptase PCR.

Results: LDH resulted in chronic pain, which further induced depressive behavior that persisted for 6 weeks after surgery. There were decreased 5-HT concentrations and upregulated TNF-α mRNA levels that were accompanied by behavioral changes. FLX treatment improved depressive behavior and moderately alleviated pain through increased 5-HT concentrations, and inhibited TNF-α mRNA expression.

Conclusions: In summary, our studies provide initial evidence that the LDH chronic pain model might serve as a model of the comorbidity of low back pain and depression. The finding that FLX improved depressive behavior and pain through normalized 5-HT concentrations and TNF-α mRNA expression establishes the initial mechanism of the comorbidity of pain and depression.