Time-Dependent Changes in the Serum Levels of Neurobiochemical Factors After Acute Methadone Overdose in Adolescent Male Rat

Chronic exposure to methadone induces activated microglia and astrocyte and cell death in the cerebellum of adult male rats

Methadone is a centrally-acting synthetic opioid analgesic widely used in the methadone maintenance therapy (MMT) programs throughout the world. Considering its neurotoxic effects particularly on the cerebellum, this study aims to address the behavioral and histological alterations in the cerebellar cortex associated with methadone administration. Twenty-four adult male albino rats were randomized into two groups of control and methadone treatment. Methadone was subcutaneously administered (2.5-10 mg/kg) once a day for two consecutive weeks. The functional and structural changes in the cerebellum were compared to the control group. Our data revealed that treating rats with methadone not only induced cerebellar atrophy, but also prompted the actuation of microgliosis, astrogliosis, and apoptotic biomarkers. We further demonstrated that treating rats with methadone increased complexity of astrocyte processes and decreased complexity of microglia processes. Our result showed that methadone impaired motor coordination and locomotor performance and neuromuscular activity. Additionally, relative gene expression of TNF-α, caspase-3 and RIPK3 increased significantly due to methadone. Our findings suggest that methadone administration has a neurodegenerative effect on the cerebellar cortex via dysregulation of microgliosis, astrogliosis, apoptosis, and neuro-inflammation.

Plasma neurofilament light levels correlate with white matter damage prior to Alzheimer's disease: results from ADNI

BACKGROUND

The blood biomarker neurofilament light (NFL) is one of the most widely used for monitoring Alzheimer's disease (AD). According to recent research, a higher NFL plasma level has a substantial predictive value for cognitive deterioration in AD patients. Diffusion tensor imaging (DTI) is an MRI-based approach for detecting neurodegeneration, white matter (WM) disruption, and synaptic damage. There have been few studies on the relationship between plasma NFL and WM microstructure integrity.

AIMS

The goal of the current study is to assess the associations between plasma levels of NFL, CSF total tau, phosphorylated tau181 (P-tau181), and amyloid-β (Aβ) with WM microstructural alterations.

METHODS

We herein have investigated the cross-sectional association between plasma levels of NFL and WM microstructural alterations as evaluated by DTI in 92 patients with mild cognitive impairment (MCI) provided by Alzheimer's Disease Neuroimaging Initiative (ADNI) participants. We analyzed the potential association between plasma NFL levels and radial diffusivity (RD), axial diffusivity (AxD), mean diffusivity (MD), and fractional anisotropy (FA) in each region of the Montreal Neurological Institute and Hospital (MNI) atlas, using simple linear regression models stratified by age, sex, and APOE ε4 genotype.

RESULTS

Our findings demonstrated a significant association between plasma NFL levels and disrupted WM microstructure across the brain. In distinct areas, plasma NFL has a negative association with FA in the fornix, fronto-occipital fasciculus, corpus callosum, uncinate fasciculus, internal capsule, and corona radiata and a positive association with RD, AxD, and MD values in sagittal stratum, corpus callosum, fronto-occipital fasciculus, corona radiata, internal capsule, thalamic radiation, hippocampal cingulum, fornix, and cingulum. Lower FA and higher RD, AxD, and MD values are related to demyelination and degeneration in WM.

CONCLUSION

Our findings revealed that the level of NFL in the blood is linked to WM alterations in MCI patients. Plasma NFL has the potential to be a biomarker for microstructural alterations. However, further longitudinal studies are necessary to validate the predictive role of plasma NFL in cognitive decline.

Central blockade of orexin type 1 receptors reduces naloxone induced activation of locus coeruleus neurons in morphine dependent rats

Orexin neuropeptides are implicated in the expression of morphine dependence. Locus coeruleus (LC) nucleus is an important brain area involving in the development of withdrawal signs of morphine and contains high expression of orexin type 1 receptors (OX1Rs). Despite extensive considerations, effects of immediate inhibition of OX1Rs by a single dose administration of SB-334867 prior to the naloxone-induced activation of LC neurons remains unknown. Therefore, we examined the direct effects of OX1Rs acute blockade on the neuronal activity of the morphine-dependent rats which underwent naloxone administration. Adult male rats underwent subcutaneous administration of 10 mg/kg morphine (two times/day) for a ten-day period. On the last day of experiment, intra-cerebroventricular administration of 10 μg/μl antagonist of OX1Rs, SB-334867, was performed just before intra-peritoneal injection of 2 mg/kg naloxone. Thereafter, in vivo extracellular single unit recording was employed to evaluate the electrical activity of LC neuronal cells. The outcomes demonstrated that morphine tolerance developed following ten-day of injection. Then, naloxone administration causes hyperactivity of LC neuronal cells, whereas a single dose administration of SB-334867 prior to naloxone prevented the enhanced activity of neurons upon morphine withdrawal. Our findings indicate that increased response of LC neuronal cells to applied naloxone could be prevented by the acute inhibition of the OX1Rs just before the naloxone treatment.