Neuroscience
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Addiction to prescribed opioids including oxycodone has reached tragic levels. Herein, we investigated the relevance of fibroblast growth factors (FGFs) and immediate early genes (IEGs) to withdrawal-induced incubation of drug craving following escalated oxycodone self-administration (SA). Rats were trained to self-administer oxycodone for 4 weeks. ⋯ Similarly, striatal c-fos and junB mRNA levels showed greater increases in LgA rats. The observations that fgf mRNA levels were more altered in the dorsal striatum than in the NAc of LgA rats suggest that changes in striatal FGF expression may be more salient to incubation of oxycodone craving than alterations in the NAc. Targeting FGF signaling pathways might offer novel strategies against opioid addiction.
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The dopamine D2 receptor (DRD2) and dopamine transporter (DAT) play a regulatory role in dopaminergic neurotransmission and thus play an important role in drug addiction. The prefrontal cortex (PFC), a critical part of the mesencephalic dopaminergic system, is thought to be involved in the development and maintenance of drug addiction. The addiction to ketamine is thought to induce behavioral effects primarily through actions on the central nervous system. ⋯ Additionally, neuronal changes in the PFC were examined by hematoxylin and eosin (HE) staining; the DRD2 and DAT mRNA and protein expression levels in the PFC were determined by real-time PCR and Western blot analysis, respectively. After 10-week ketamine administration, the assessment of the manifestations of toxicity in rhesus monkeys revealed significant changes in body weight and behavior, decreased DRD2 and DAT mRNA and protein expression in the PFC, and histological abnormalities including neuronal eosinophilia, pyknosis and disorderly arrangement of neurons in the PFC. These results suggest that the reduced expression of DRD2 and DAT in PFC could be involved in the behavioral and the neurological changes induced by ketamine administration, which may play an important role in the molecular mechanisms of ketamine addiction.
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The striatum mediates habit formation and reward association. The striatum can be divided into the patch and matrix compartment, which are two distinct regions that sub-serve different aspects of behavior. The patch compartment may mediate reward-related behaviors, while the matrix compartment may mediate adaptive motor functions. ⋯ Our data showed that patch compartment lesions in the dorsolateral striatum reduced the reinstatement of sucrose self-administration after sucrose devaluation, indicating that destruction of this region prevented the development of habitual behavior. Additionally, in animals with patch compartment lesions in the DLS that did not develop habitual behavior, activation of the dorsolateral striatum and sensorimotor cortex was diminished, while activity in the dorsomedial striatum and prefrontal cortex was increased, suggesting less engagement of regions that mediate habitual behaviors and heightened engagement of regions that mediate goal-directed behaviors occurs with reduced habit formation. These data indicate that the dorsolateral patch compartment may mediate habit formation by altering information flow through basal ganglia circuits.
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Sushi repeat-containing protein X-linked 2 (SRPX2) is a novel hypothalamic protein and a ligand of the urokinase-type plasminogen activator receptor (uPAR), which is essential for proteolysis of extracellular matrix and tissue remodeling after an insult to the brain. However, little is known about regulation of SRPX2. Our objective was to investigate if SRPX2 expression is altered by (i) the deficiency of uPAR or uPA (urokinase-type plasminogen activator), and (ii) traumatic brain injury (TBI). ⋯ Unsupervised hierarchical clustering using SRPX2 expression did not identify genotype or injury-specific clusters. Our data demonstrate that SRPX2 expression in the hypothalamus is resistant to genetic deficiencies in the urokinase-system or to the hypothalamus-affecting TBI. The contribution of elevated Srpx2 gene expression in perilesional cortex to post-TBI recovery process, however, requires further exploration.
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Chronic cerebral hypoperfusion (CCH) is an important pathophysiological basis for AD and vascular cognitive impairment (VCI), but the underlying mechanisms are not completely clear. Age-related mitochondrial aging-like changes were closely associated with nervous system diseases and ischemia. This study aimed to observe the changes of cognitive function and hippocampal mitochondrial aging in rats with CCH. ⋯ CCH induced long-term spatial learning and memory deficits. The related alterations of mitochondrial aging and alpha-synuclein in the hippocampus are crucial for VCI pathogenesis.