Combined treatment with subchronic lithium and acute intracerebral mirtazapine microinjection into the median raphe nucleus exerted an anxiolytic-like effect synergistically

Sex difference affects fear extinction but not lithium efficacy in rats following fear-conditioning with respect to the hippocampal level of BDNF

In rodents, exposure to electrical shock and creating a strong fear memory using fear-conditioning model can induce PTSD-like behavior. In this study, we induced a fear-conditioning model in rats and investigated freezing (PTSD-like) behavior, 21 days after three shocks exposure (0.6 mA, 3 s, 30 seconds interval) in both male and female rats. Lithium was injected intraperitoneally (100 mg/kg) in three protocols: (1) 1 h after fear-conditioning (2) 1 h, 24 h, and 48 h after fear-conditioning (3), 1 h, 24 h, 48 h, 72 h, and 96 h after fear-conditioning. Extinction training (20 sounds without shocks, 75 dB, 3 s, 30 seconds interval) was performed in three protocols: (1) 1 h after fear-conditioning (one session), (2) 1 h, 24 h, and 48 h after fear-conditioning (three sessions), (3), 1 h, 24 h, 48 h, 72 h, and 96 h after fear-conditioning (five sessions). Forced swim test (FST) and hot plate were used to assess behavior. Results showed that lithium in all protocols had no effect on freezing behavior, FST, and pain subthreshold in all rats. Extinction training decreased freezing behavior, with more efficacy in females. In males, only 5-session training was effective, while in females all protocols were effective. Extinction training also altered pain perception and the results of FST, depending on the sessions and was different in males and females. Brain-derived neurotrophic factor (BDNF) mRNA level was increased in females following 3 and 5 sessions, and in males following 5 sessions extinction training. In conclusion, we suggested that there is a sex difference for the effect of extinction training on freezing behavior and BDNF mRNA level in a rat model of fear-conditioning.

Connection Input Mapping and 3D Reconstruction of the Brainstem and Spinal Cord Projections to the CSF-Contacting Nucleus

Objective

To investigate whether the CSF-contacting nucleus receives brainstem and spinal cord projections and to understand the functional significance of these connections.

Methods

The retrograde tracer cholera toxin B subunit (CB) was injected into the CSF-contacting nucleus in Sprague-Dawley rats according the previously reported stereotaxic coordinates. After 7–10 days, these rats were perfused and their brainstem and spinal cord were sliced (thickness, 40 μm) using a freezing microtome. All the sections were subjected to CB immunofluorescence staining. The distribution of CB-positive neuron in different brainstem and spinal cord areas was observed under fluorescence microscope.

Results

The retrograde labeled CB-positive neurons were found in the midbrain, pons, medulla oblongata, and spinal cord. Four functional areas including one hundred and twelve sub-regions have projections to the CSF-contacting nucleus. However, the density of CB-positive neuron distribution ranged from sparse to dense.

Conclusion

Based on the connectivity patterns of the CSF-contacting nucleus receives anatomical inputs from the brainstem and spinal cord, we preliminarily conclude and summarize that the CSF-contacting nucleus participates in pain, visceral activity, sleep and arousal, emotion, and drug addiction. The present study firstly illustrates the broad projections of the CSF-contacting nucleus from the brainstem and spinal cord, which implies the complicated functions of the nucleus especially for the unique roles of coordination in neural and body fluids regulation.

Clinical Therapeutic Strategy and Neuronal Mechanism Underlying Post-Traumatic Stress Disorder (PTSD)

Post-traumatic stress disorder (PTSD) is characterized by an exaggerated response to contextual memory and impaired fear extinction, with or without mild cognitive impairment, learning deficits, and nightmares. PTSD is often developed by traumatic events, such as war, terrorist attack, natural calamities, etc. Clinical and animal studies suggest that aberrant susceptibility of emotion- and fear-related neurocircuits, including the amygdala, prefrontal cortex (PFC), and hippocampus may contribute to the development and retention of PTSD symptoms. Psychological and pharmacological therapy, such as cognitive behavioral therapy (CBT), and treatment with anti-depressive agents and/or antipsychotics significantly attenuate PTSD symptoms. However, more effective therapeutics are required for improvement of quality of life in PTSD patients. Previous studies have reported that ω3 long-chain polyunsaturated fatty acid (LCPUFA) supplements can suppress the development of PTSD symptoms. Fatty acid binding proteins (FABPs) are essential for LCPUFA intracellular trafficking. In this review, we have introduced Fabp3 null mice as an animal model of PTSD with impaired fear extinction. Moreover, we have addressed the neuronal circuits and novel therapeutic strategies for PTSD symptoms.

Mirtazapine attenuates anxiety- and depression-like behaviors in rats during cocaine withdrawal

BACKGROUND

Anxiety and depression, key symptoms of the cocaine withdrawal syndrome in human addicts, are considered the main factors that precipitate relapse in chronic cocaine addiction. Preclinical studies have found that rodents exposed to different withdrawal periods show an increase in anxiety and depressive-like behavior. Mirtazapine - a tetracyclic medication - is used primarily to treat depression and, sometimes, anxiety. It has also successfully improved withdrawal symptoms in drug-dependent patients.

AIM

This study sought to determine whether chronic dosing of mirtazapine during cocaine withdrawal reduced depression- and anxiety-like behaviors that characterize cocaine withdrawal in animals.

METHODS

Cocaine pre-treated Wistar rats were subjected to a 60-day cocaine withdrawal period during which depression- and anxiety-like behaviors were evaluated in open field tests (OFT), the elevated plus-maze (EPM), the light-dark box test (LDT), the forced swimming test (FST) and spontaneous locomotor activity (SLA).

RESULTS

We found that chronic dosing with different doses of mirtazapine (30 and 60 mg/kg) decreased depression- and anxiety-like behaviors induced by different doses of cocaine (10, 20 and 40 mg/kg) during the 60-day cocaine withdrawal.

INTERPRETATION

Our results suggest that the pharmacological effect of mirtazapine on its target sites of action (α₂-adrenergic and 5-HT_2A and 5-HT₃ receptors) within the brain may improve depression- and anxiety-like behaviors for long periods.

CONCLUSION

Therefore, the findings support the use of mirtazapine as a potentially effective therapy to reduce anxiety and depressive-like behavior during cocaine withdrawal.