ΔFosB: A Molecular Mechanism of MDMA Dependence

<p>Rationale. 3,4-methylenedioxymethamphetamine (MDMA) is a widely used illicit substance and some users show signs of abuse and dependence. It has been suggested that addiction reflects persistent neuroplasticity and one proposed mechanism has been a change in the expression of the transcription factor, ΔFosB. Objectives. This study determined whether ΔFosB expression in reward-relevant brain areas was altered as a function of MDMA self-administration. Methods. Rats were separated into triads. One rat self-administered MDMA (master rat) and the other 2 rats received either MDMA (yoked MDMA) or saline (yoked saline) infusions contingent on the behaviour of the master rat. Testing continued until a total intake of 350 mg/kg of MDMA was delivered. Two days following the final self-administration session, rats were sacrificed and perfused transcardially. Brains were removed, and ΔFosB immunohistochemistry was conducted. ΔFosB expression in striatum and medial prefrontal cortex was compared across groups. Results. Unfortunately the tissue from many of the yoked MDMA rats was compromised and therefore data from this group were not included in any analyses. MDMA self-administration produced a significantly greater expression of ΔFosB in the ventromedial and ventrolateral portions of the caudate putamen when compared to expression produced following yoked saline exposure. Within the infralimbic cortex, accumbens shell and dorsolateral caudate putamen differences approached significance. A significant correlation between ΔFosB expression in the ventromedial caudate putamen and cumulative active lever presses across the final 5 days of self-administration was also found. Conclusions. These findings provide the first evidence of MDMA-induced expression of ΔFosB. Increased expression of ΔFosB was observed in regions associated with the development and maintenance of drug addiction. These data support the idea that induction of ΔFosB may present a mechanism by which MDMA can induce alterations in genetic transcription, which may underlie the development of MDMA dependence. Future studies should utilise antagonism of ΔFosB via region-selective administration of Δc-jun in order to further elucidate the role of these transcriptional changes in the development and maintenance of self-administration.</p>

ΔFosB: A Molecular Mechanism of MDMA Dependence

<p>Rationale. 3,4-methylenedioxymethamphetamine (MDMA) is a widely used illicit substance and some users show signs of abuse and dependence. It has been suggested that addiction reflects persistent neuroplasticity and one proposed mechanism has been a change in the expression of the transcription factor, ΔFosB. Objectives. This study determined whether ΔFosB expression in reward-relevant brain areas was altered as a function of MDMA self-administration. Methods. Rats were separated into triads. One rat self-administered MDMA (master rat) and the other 2 rats received either MDMA (yoked MDMA) or saline (yoked saline) infusions contingent on the behaviour of the master rat. Testing continued until a total intake of 350 mg/kg of MDMA was delivered. Two days following the final self-administration session, rats were sacrificed and perfused transcardially. Brains were removed, and ΔFosB immunohistochemistry was conducted. ΔFosB expression in striatum and medial prefrontal cortex was compared across groups. Results. Unfortunately the tissue from many of the yoked MDMA rats was compromised and therefore data from this group were not included in any analyses. MDMA self-administration produced a significantly greater expression of ΔFosB in the ventromedial and ventrolateral portions of the caudate putamen when compared to expression produced following yoked saline exposure. Within the infralimbic cortex, accumbens shell and dorsolateral caudate putamen differences approached significance. A significant correlation between ΔFosB expression in the ventromedial caudate putamen and cumulative active lever presses across the final 5 days of self-administration was also found. Conclusions. These findings provide the first evidence of MDMA-induced expression of ΔFosB. Increased expression of ΔFosB was observed in regions associated with the development and maintenance of drug addiction. These data support the idea that induction of ΔFosB may present a mechanism by which MDMA can induce alterations in genetic transcription, which may underlie the development of MDMA dependence. Future studies should utilise antagonism of ΔFosB via region-selective administration of Δc-jun in order to further elucidate the role of these transcriptional changes in the development and maintenance of self-administration.</p>

GABAB receptor signaling in the caudate putamen is involved in binge-like consumption during a high fat diet in mice

Previous studies suggest that signaling by the gamma-aminobutyric acid (GABA) type B receptor (GABABR) is involved in the regulation of binge eating, a disorder which might contribute to the development of obesity. Here, we show that intermittent access to a high fat diet (HFD) induced binge-like eating behavior with activation of dopamine receptor d1 (drd1)-expressing neurons in the caudate putamen (CPu) and nucleus accumbens (NAc) in wild-type (WT) mice. The activation of drd1-expressing neurons during binge-like eating was substantially increased in the CPu, but not in the NAc, in corticostriatal neuron-specific GABABR-deficient knockout (KO) mice compared to WT mice. Treatment with the GABABR agonist, baclofen, suppressed binge-like eating behavior in WT mice, but not in KO mice, as reported previously. Baclofen also suppressed the activation of drd1-expressing neurons in the CPu, but not in the NAc, during binge-like eating in WT mice. Thus, our data suggest that GABABR signaling in CPu neurons expressing drd1 suppresses binge-like consumption during a HFD in mice.

Metabolic Brain Network Analysis With 18F-FDG PET in a Rat Model of Neuropathic Pain

Neuropathic pain has been found to be related to profound reorganization in the function and structure of the brain. We previously demonstrated changes in local brain activity and functional/metabolic connectivity among selected brain regions by using neuroimaging methods. The present study further investigated large-scale metabolic brain network changes in 32 Sprague–Dawley rats with right brachial plexus avulsion injury (BPAI). Graph theory was applied in the analysis of 2-deoxy-2-[18F] fluoro-D-glucose (18F-FDG) PET images. Inter-subject metabolic networks were constructed by calculating correlation coefficients. Global and nodal network properties were calculated and comparisons between pre- and post-BPAI (7 days) status were conducted. The global network properties (including global efficiency, local efficiency and small-world index) and nodal betweenness centrality did not significantly change for all selected sparsity thresholds following BPAI (p &gt; 0.05). As for nodal network properties, both nodal degree and nodal efficiency measures significantly increased in the left caudate putamen, left medial prefrontal cortex, and right caudate putamen (p &lt; 0.001). The right entorhinal cortex showed a different nodal degree (p &lt; 0.05) but not nodal efficiency. These four regions were selected for seed-based metabolic connectivity analysis. Strengthened connectivity was found among these seeds and distributed brain regions including sensorimotor area, cognitive area, and limbic system, etc. (p &lt; 0.05). Our results indicated that the brain had the resilience to compensate for BPAI-induced neuropathic pain. However, the importance of bilateral caudate putamen, left medial prefrontal cortex, and right entorhinal cortex in the network was strengthened, as well as most of their connections with distributed brain regions.

IGF-1 Gene Therapy Modifies Inflammatory Environment and Gene Expression in the Caudate-Putamen of Aged Female Rat Brain

Brain aging is characterized by chronic neuroinflammation caused by activation of glial cells, mainly microglia, leading to alterations in homeostasis of the central nervous system. Microglial cells are constantly surveying their environment to detect and respond to diverse signals. During aging, microglia undergo a process of senescence, characterized by loss of ramifications, spheroid formation, and fragmented processes, among other abnormalities. Therefore, the study of microglia senescence is of great relevance to understand age‐related declines in cognitive and motor function.We have targeted the deleterious effects of aging by implementing gene therapy with IGF-1, employing recombinant adenoviral vectors (RAds) as a delivery system. In this study, we performed intracerebroventricular (ICV) IGF-1 gene therapy on aged female rats and evaluated its effect on Caudate-Putamen unit (CPu) gene expression and inflammatory state. IGF-1 gene therapy modified senescent microglia of the CPu towards an anti-inflammatory state increasing the proportion of Iba1+Arg1+ cells. Moreover, IGF-1 gene therapy was able to regulate the pro-inflammatory environment of CPu in female aged rats by down-regulating the expression of genes typically over-expressed during aging. Our results demonstrate that, ICV IGF-1 gene therapy, is capable to modulate microglia cells and CPu gene expression, leading to an improvement in motor function.

Immunohistochemical analysis of microglial changes in the experimental acute hepatic encephalopathy

Hepatic encephalopathy (HE) is a syndrome of impaired brain function in patients with advanced liver failure and it manifests in form of psychometric tests alterations up to decreased consciousness and coma. The current knowledge about HE mainly focused on the theory of ammonia neurotoxicity and neuroinflammation. Microglia being resident innate immune cells of the brain when activated are responsible for the neuroinflammatory reactions. The aim – immunohistochemical study of the microglial changes in different rat brain regions in conditions of experimental acute HE (AHE). Materials and methods. We used acetaminophen induced liver failure model in Wistar rats. Four from 10 animals that survived up to 24 h after acetaminophen injection constituted “compensated group”; 6 animals which died within 24 h – “decompensated group”. Microglial reactive changes were analysed by the evaluation of the relative area (S rel., %) of CD68+ expression in the brain cells not associated with meninges and vessels, as well as the changing in shape and number of these cells. Results. Acetaminophen-induced AHE in rats was characterized by the regional- and time-dependent dynamic increase in CD68 expression level in the rat brain in form of significant (relatively to control) increase of CD68+ S rel. in brain cells and the number of such cells. The medians of CD68+ S rel. and their numbers in significantly changed regions of non-survived rats were, respectively: subcortical white matter – 0.24 (0.20; 0.26) and 11.00 (8.00; 13.00); thalamus – 0.13 (0.90; 0.18) and 6.00 (3.00; 7.00); caudate/putamen – 0.13 (0.12; 0.18) and 7.00 (4.00; 11.00) – all indicators were statistically significant compared to control. In the survived animals, indicators were, respectively: subcortical white matter – 0.24 (0.16; 0,26) and 10.00 (8.00; 12.00); caudate/putamen – 0.12 (0.10; 0.15) and 6.00 (4.00; 10.00) – the differences were significant compared to control. Conclusions. The highest and significant indicators were revealed at 24 h (compared to earlier time points) of the experiment in the white matter, thalamus and caudate/putamen. This fact reflects time-dependent dynamic boosting of reactive changes in microglia and presumably may indicate the regions of the most active neuroinflammatory response within the brain parenchyma in the conditions of AHE. The appearing of a small percentage of cells with amoeboid transformation among CD68+-cells may mean partial functional insufficiency of such cells due to probable suppressive impact of ammonia or other influencing factors, as well as insignificance of the material that needs to be phagocytosed under established conditions.