Biomedical subjects

Alipi Naydenov

Publications and source records attributed to Alipi Naydenov.

3 recordsLinked to original sources

PubMed2006

Brain reward regulated by AMPA receptor subunits in nucleus accumbens shell.

Drugs of abuse alter expression of AMPA-type glutamate receptor subunits (GluRs) in the nucleus accumbens (NAc), a key component of brain reward systems. The impact of this regulation on general motivational states is unclear. Here, we used herpes simplex virus vectors to examine how transient increases in the expression of GluR1 or GluR2 protein in the shell component of NAc affect the rewarding impact of electrical stimulation of the medial forebrain bundle, as reflected by intracranial self-stimulation (ICSS) thresholds in rats. We found that elevated GluR1 in NAc shell increases ICSS thresholds, an effect similar to that caused by treatments that cause anhedonia and dysphoria (prodepressive effects) in rats and humans (e.g., drug withdrawal, kappa-opioid agonists). In contrast, elevated GluR2 decreases ICSS thresholds, an effect similar to that caused by rewarding treatments (e.g., drugs of abuse). To confirm that viral vector-mediated elevations of GluR1 in the NAc shell produce molecular consequences that are different from those of elevated GluR2, we examined the expression of a set of drug-regulated genes 3 d after treatment using quantitative PCR. Elevated GluR1 was accompanied by sustained increases in the gene for GluR1, whereas elevated GluR2 was accompanied by decreases in prodynorphin. These data suggest that GluR1 and GluR2 in the NAc shell play opposing roles in the regulation of motivated behavior.

Analysis of Variance↗

PubMed2006

Lithium administration to preadolescent rats causes long-lasting increases in anxiety-like behavior and has molecular consequences.

Lithium (Li) is frequently used in the treatment of bipolar disorder (BPD), a debilitating condition that is increasingly diagnosed in children and adolescents. Because the symptoms of BPD in children are different from the typical symptoms in adulthood and have significant overlap with other childhood psychiatric disorders, this disorder is notoriously difficult to diagnose. This raises the possibility that some children not affected by BPD are treated with Li during key periods of brain development. The objective of this investigation was to examine the long-term effects of Li on the developing brain via a series of behavioral and molecular studies in rats. Rat pups were reared on Li chow for 3 weeks. Parallel groups were tested while on Li chow or 2 and 6 weeks after discontinuation of treatment. We found increased measures of anxiety-like behavior at all times tested. Gene microarray studies of the amygdala revealed that Li affected the expression of gene transcripts of the synapse and the cytoskeleton, suggesting that the treatment induced synaptic adjustments. Our study indicates that Li can alter the trajectory of brain development. Although the effects of Li on the normal brain seems unfavorable, effects on the abnormal brain cannot be determined from these studies alone and may well be therapeutic. Our results indicate that Li administration to the normal brain has the potential for lasting adverse effects.

Administration, Oral↗

PubMed2006

Decrease in creatine kinase messenger RNA expression in the hippocampus and dorsolateral prefrontal cortex in bipolar disorder.

OBJECTIVES: Bipolar disorder (BPD) affects more than 2 million adults in the USA and ranks among the top 10 causes of worldwide disabilities. Despite its prevalence, very little is known about the etiology of BPD. Recent evidence suggests that cellular energy metabolism is disturbed in BPD. Mitochondrial function is altered, and levels of high-energy phosphates, such as phosphocreatine (PCr), are reduced in the brain. This evidence has led to the hypothesis that deficiencies in energy metabolism could account for some of the pathophysiology observed in BPD. To further explore this hypothesis, we examined levels of creatine kinase (CK) mRNA, the enzyme involved in synthesis and metabolism of PCr, in the hippocampus (HIP) and dorsolateral prefrontal cortex (DLPFC) of control, BPD and schizophrenia subjects. METHODS: Tissue was obtained from the Harvard Brain Tissue Resource Center. Real-time quantitative polymerase chain reaction (HIP, DLPFC) and gene expression microarrays (HIP) were employed to compare the brain and mitochondrial 1 isoforms of CK. RESULTS: Both CK isoforms were downregulated in BPD. Furthermore, mRNA transcripts for oligodendrocyte-specific proteins were downregulated in the DLPFC, whereas the mRNA for the neuron-specific protein microtubule-associated protein 2 was downregulated in the HIP. CONCLUSION: Although some of the downregulation of CK might be explained by cell loss, a more general mechanism seems to be responsible. The downregulation of CK transcripts, if translated into protein levels, could explain the reduction of high-energy phosphates previously observed in BPD.

Adult↗