Making bloodwork work: the impact of sample collection, processing, and storage on plasma glutathione measurement, and implications for translation.

Psychiatry has traditionally focused on the study of neurons and neurotransmitter physiology in the pathophysiology and treatment of psychiatric disorders. A growing literature highlights REDOX imbalance (a state in which demand for antioxidants surpasses their bioavailability) as a common pathophysiology for a diverse array of brain conditions (e.g., trichotillomania, schizophrenia, autism, Parkinson's disease). REDOX imbalance is typically measured via plasma glutathione, as glutathione is critical to the adaptive antioxidant response in the brain. Accordingly, glutathione, its precursors, and/or metabolites serve as biomarkers of disease risk, therapeutic targets, and measures of treatment response. However, as with any emerging field, there are currently several different methods for collection, processing, storage, and calculation of summary measures of plasma glutathione metabolism, within and between preclinical and clinical research. The lack of evidence-based best-practice methodology hampers reproducibility (preclinical or clinical), and translation (between preclinical and clinical work). To address this methodological need, here we used a repeated measures within-subject design to investigate how sample preparation (type of anticoagulant used during blood collection, deproteinization status, and storage temperature) affects plasma glutathione levels. Accordingly, we collected whole blood from mice (N = 13), and then, using a commercially available kit, quantified glutathione in plasma stored in four different ways. Presuming that these preparation conditions and post-processing calculations are unimportant, we would expect to see no difference in glutathione levels and summary measures from the same sample. However, we found each of these variables to significantly alter quantified glutathione levels. Accordingly, we propose a vital, gold-standard methodology for both sample collection, processing, and storage of plasma used for glutathione quantification and for summary calculations of glutathione that can be used preclinically and clinically, thus yielding more streamlined translation.

Pebble to the Metal: A Boulder Approach to Enrichment for Danio rerio.

Zebrafish are an established and widely used animal model, yet there is limited understanding of their welfare needs. Despite an increasing number of studies on zebrafish enrichment, in-tank environmental enrichment remains unpopular among researchers. This is due to perceived concerns over health/hygiene when it comes to introducing enrichment into the tank, although actual evidence for this is sparse. To accommodate this belief, regardless of veracity, we tested the potential benefits of enrichments presented outside the tank. Thus, we investigated the preferences and physiological stress of zebrafish with pictures of pebbles placed underneath the tank. We hypothesized that zebrafish would show a preference for enriched environments and have lower stress levels than barren housed zebrafish. In our first experiment, we housed zebrafish in a standard rack system and recorded their preference for visual access to a pebble picture, with two positive controls: visual access to conspecifics, and group housing. Using a crossover repeated-measures factorial design, we tested if the preference for visual access to pebbles was as strong as the preference for social contact. Zebrafish showed a strong preference for visual access to pebbles, equivalent to that for conspecifics. Then, in a second experiment, tank water cortisol was measured to assess chronic stress levels of zebrafish housed with or without a pebble picture under their tank, with group housing as a positive control. Cortisol levels were significantly reduced in zebrafish housed with pebble pictures, as were cortisol levels in group housed zebrafish. In fact, single housed zebrafish with pebble pictures showed the same cortisol levels as group housed zebrafish without pebble pictures. Thus, the use of an under-tank pebble picture was as beneficial as being group housed, effectively compensating for the stress of single housing. Pebble picture enrichment had an additive effect with group housing, where group housed zebrafish with pebble pictures had the lowest cortisol levels of any treatment group.

Prefrontal Regulation of Punished Ethanol Self-administration.

BACKGROUND: A clinical hallmark of alcohol use disorder is persistent drinking despite potential adverse consequences. The ventromedial prefrontal cortex (vmPFC) and dorsomedial prefrontal cortex (dmPFC) are positioned to exert top-down control over subcortical regions, such as the nucleus accumbens shell (NAcS) and basolateral amygdala, which encode positive and negative valence of ethanol (EtOH)-related stimuli. Prior rodent studies have implicated these regions in regulation of punished EtOH self-administration (EtOH-SA). METHODS: We conducted in vivo electrophysiological recordings in mouse vmPFC and dmPFC to obtain neuronal correlates of footshock-punished EtOH-SA. Ex vivo recordings were performed in NAcS D1 receptor-expressing medium spiny neurons receiving vmPFC input to examine punishment-related plasticity in this pathway. Optogenetic photosilencing was employed to assess the functional contribution of the vmPFC, dmPFC, vmPFC projections to NAcS, or vmPFC projections to basolateral amygdala, to punished EtOH-SA. RESULTS: Punishment reduced EtOH lever pressing and elicited aborted presses (lever approach followed by rapid retraction). Neurons in the vmPFC and dmPFC exhibited phasic firing to EtOH lever presses and aborts, but only in the vmPFC was there a population-level shift in coding from lever presses to aborts with punishment. Closed-loop vmPFC, but not dmPFC, photosilencing on a postpunishment probe test negated the reduction in EtOH lever presses but not in aborts. Punishment was associated with altered plasticity at vmPFC inputs to D1 receptor-expressing medium spiny neurons in the NAcS. Photosilencing vmPFC projections to the NAcS, but not to the basolateral amygdala, partially reversed suppression of EtOH lever presses on probe testing. CONCLUSIONS: These findings demonstrate a key role for the vmPFC in regulating EtOH-SA after punishment, with implications for understanding the neural basis of compulsive drinking in alcohol use disorder.