Quantitative validation of immunofluorescence and lectin staining using reduced CLARITY acrylamide formulations.

The CLARITY technique enables three-dimensional visualization of fluorescent-labeled biomolecules in clarified intact brain samples, affording a unique view of molecular neuroanatomy and neurocircuitry. It is therefore, essential to find the ideal combination for clearing tissue and detecting the fluorescent-labeled signal. This method requires the formation of a formaldehyde-acrylamide fixative-generated hydrogel mesh through which cellular lipid is removed with sodium dodecyl sulfate. Several laboratories have used differential acrylamide and detergent concentrations to achieve better tissue clearing and antibody penetration, but the potential effects upon fluorescent signal retention is largely unknown. In an effort to optimize CLARITY processing procedures we performed quantitative parvalbumin immunofluorescence and lectin-based vasculature staining using either 4 or 8% sodium dodecyl sulfate detergent in combination with different acrylamide formulas in mouse brain slices. Using both confocal and CLARITY-optimized lightsheet microscope-acquired images, we demonstrate that 2% acrylamide monomer combined with 0.0125% bis-acrylamide and cleared with 4% sodium dodecyl sulfate generally provides the most optimal signal visualization amongst various hydrogel monomer concentrations, lipid removal times, and detergent concentrations.

Nucleus accumbens cocaine-amphetamine regulated transcript mediates food intake during novelty conflict.

Obesity is a persistent and pervasive problem, particularly in industrialized nations. It has come to be appreciated that the metabolic health of an individual can influence brain function and subsequent behavioral patterns. To examine the relationship between metabolic phenotype and central systems that regulate behavior, we tested rats with divergent metabolic phenotypes (Low Capacity Runner: LCR vs. High Capacity Runner: HCR) for behavioral responses to the conflict between hunger and environmental novelty using the novelty suppressed feeding (NSF) paradigm. Additionally, we measured expression of mRNA, for peptides involved in energy management, in response to fasting. Following a 24-h fast, LCR rats showed lower latencies to begin eating in a novel environment compared to HCR rats. A 48-h fast equilibrated the latency to begin eating in the novel environment. A 24-h fast differentially affected expression of cocaine-amphetamine regulated transcript (CART) mRNA in the nucleus accumbens (NAc), where 24-h of fasting reduced CART mRNA in LCR rats. Bilateral microinjections of CART 55-102 peptide into the NAc increased the latency to begin eating in the NSF paradigm following a 24-h fast in LCR rats. These results indicate that metabolic phenotype influences how animals cope with the conflict between hunger and novelty, and that these differences are at least partially mediated by CART signaling in the NAc. For individuals with poor metabolic health who have to navigate food-rich and stressful environments, changes in central systems that mediate conflicting drives may feed into the rates of obesity and exacerbate the difficulty individuals have in maintaining weight loss.