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Background: The cytosolic 5'-nucleotidase II (NT5C2) enzyme has been implicated in both psychiatric disorders and metabolic traits, but whether these associations reflect a shared biological basis remains unclear. Here we combined cross-species approaches to investigate how reduced NT5C2 function shapes behavior.

Results: In Drosophila melanogaster, neuronal knockdown of the ortholog dNT5B increased activity around light-dark transitions, reduced sleep fragmentation, and selectively suppressed food intake under satiated conditions. Moreover, analysis of mouse phenotyping data revealed that whole-body Nt5c2 knockout alters locomotor activity, sensorimotor gating, and anxiety-related behaviors. Finally, human variant-trait associations showed reproducible enrichment in both metabolic domains, including body composition and BMI, and neuro-psychiatric outcomes such as schizophrenia, smoking, and anxiety.

Conclusions: Together, these phenotypic findings indicate that NT5C2 is a conserved neuro-metabolic regulator, linking energy-related pathways to specific behavioral dimensions that may underlie its pleiotropic impact on psychiatric and metabolic risk.

In the mammalian brain, new neurons continue to be generated throughout life in a process known as adult neurogenesis. The role of adult-generated neurons has been broadly studied across laboratories, and mounting evidence suggests a strong link to the HPA axis and concomitant dysregulations in patients diagnosed with mood disorders. Psychedelic compounds, such as phenethylamines, tryptamines, cannabinoids, and a variety of ever-growing chemical categories, have emerged as therapeutic options for neuropsychiatric disorders, while numerous reports link their effects to increased adult neurogenesis. In this systematic review, we examine studies assessing neurogenesis or other neurogenesis-associated brain plasticity after psychedelic interventions and aim to provide a comprehensive picture of how this vast category of compounds regulates the generation of new neurons. We conducted a literature search on PubMed and Science Direct databases, considering all articles published until January 31, 2023, and selected articles containing both the words "neurogenesis" and "psychedelics". We analyzed experimental studies using either in vivo or in vitro models, employing classical or atypical psychedelics at all ontogenetic windows, as well as human studies referring to neurogenesis-associated plasticity. Our findings were divided into five main categories of psychedelics: CB1 agonists, NMDA antagonists, harmala alkaloids, tryptamines, and entactogens. We described the outcomes of neurogenesis assessments and investigated related results on the effects of psychedelics on brain plasticity and behavior within our sample. In summary, this review presents an extensive study into how different psychedelics may affect the birth of new neurons and other brain-related processes. Such knowledge may be valuable for future research on novel therapeutic strategies for neuropsychiatric disorders.

In medical and biomedical education, traditional teaching methods often struggle to engage students and promote critical thinking. The use of AI language models has the potential to transform teaching and learning practices by offering an innovative, active learning approach that promotes intellectual curiosity and deeper understanding. To effectively integrate AI language models into biomedical education, it is essential for educators to understand the benefits and limitations of these tools and how they can be employed to achieve high-level learning outcomes. This article explores the use of AI language models in biomedical education, focusing on their application in both classroom teaching and learning assignments. Using the SOLO taxonomy as a framework, I discuss strategies for designing questions that challenge students to exercise critical thinking and problem-solving skills, even when assisted by AI models. Additionally, I propose a scoring rubric for evaluating student performance when collaborating with AI language models, ensuring a comprehensive assessment of their learning outcomes. AI language models offer a promising opportunity for enhancing student engagement and promoting active learning in the biomedical field. Understanding the potential use of these technologies allows educators to create learning experiences that are fit for their students' needs, encouraging intellectual curiosity and a deeper understanding of complex subjects. The application of these tools will be fundamental to provide more effective and engaging learning experiences for students in the future.

MK-801, also called dizocilpine, is an N-methyl-D-aspartate (NMDA) receptor antagonist widely used in animal research to model schizophrenia-like phenotypes. Although its effects in rodents are well characterised, little is known about the outcomes of this drug in other organisms. In this study, we characterise the effects of MK-801 on the locomotion, sleep, and negative geotaxis of the fruit fly Drosophila melanogaster. We observed that acute (24 h) and chronic (7 days) administration of MK-801 enhanced negative geotaxis activity in the forced climbing assay for all tested concentrations (0.15 mM, 0.3 mM, and 0.6 mM). Moreover, acute administration, but not chronic, increased the flies' locomotion in a dose-dependent matter. Finally, average sleep duration was not affected by any concentration or administration protocol. Our results indicate that acute MK-801 could be used to model hyperactivity phenotypes in Drosophila melanogaster. Overall, this study provides further evidence that the NMDA receptor system is functionally conserved in flies, suggesting the usefulness of this model to investigate several phenotypes as a complement and replacement of the rodent models within drug discovery.

Simple Summary In our study, we looked at a behavior called prepulse inhibition (PPI) in Drosophila melanogaster, commonly known as the fruit fly. For many animals, the sudden presentation of strong sensorial stimuli can induce a defensive response or motor reflex. PPI is a phenomenon where a small stimulus, named "prepulse," is presented shortly before a larger stimulus, so the larger stimulus induces a weaker response than it normally would. This behavior is seen in many different types of animals and is used to study conditions such as anxiety and schizophrenia. For this study, the chosen stimulus is the sudden presentation of one-second darkness, or lights-off, shown to evoke an immediate locomotion response in Drosophila. Our research found that PPI can also be seen in adult flies, which has not been reported before. Additionally, we confirmed our results by showing that a drug that affects an important brain component, called the NMDA receptor, can change PPI in flies. We suggest that studying this behavior in fruit flies could help us understand how it works in other animals, including humans. Prepulse inhibition (PPI) is a widely investigated behavior to study the mechanisms of disorders such as anxiety, schizophrenia, and bipolar mania. PPI has been observed across various vertebrate and invertebrate species; however, it has not yet been reported in adult Drosophila melanogaster. In this study, we describe the first detection of PPI of visually evoked locomotor arousal in flies. To validate our findings, we demonstrate that PPI in Drosophila can be partially reverted by the N-methyl D-aspartate (NMDA) receptor antagonist MK-801, known for inducing sensorimotor gating deficits in rodent models. Additionally, we show that the visually evoked response can be inhibited by multiple stimuli presentation, which can also be affected by MK-801. Given the versatility of Drosophila as a model organism for genetic screening and analysis, our results suggest that high-throughput behavioral screenings of adult flies can become a valuable tool for investigating the mechanisms behind PPI.

Background: Like most living organisms, the fruit fly Drosophila melanogaster exhibits strong and diverse behavioural reactions to light. Drosophila is a diurnal animal that displays both short- and long-term responses to light, important for, instance, in avoidance and light wavelength preference, regulation of eclosion, courtship, and activity, and provides an important model organism for understanding the regulation of circadian rhythms both at molecular and circuit levels. However, the assessment and comparison of light-based behaviours is still a challenge, mainly due to the lack of a standardised platform to measure behaviour and different protocols created across studies. Here, we describe the Drosophila Interactive System for Controlled Optical manipulations (DISCO), a low-cost, automated, high-throughput device that records the flies' activity using infrared beams while performing LED light manipulations.

Results: To demonstrate the effectiveness of this tool and validate its potential as a standard platform, we developed a number of distinct assays, including measuring the locomotor response of flies exposed to sudden darkness (lights-off) stimuli. Both white-eyed and red-eyed wild-type flies exhibit increased activity after the application of stimuli, while no changes can be observed in Fmr1 null allele flies, a model of fragile X syndrome. Next, to demonstrate the use of DISCO in long-term protocols, we monitored the circadian rhythm of the flies for 48 h while performing an alcohol preference test. We show that increased alcohol consumption happens intermittently throughout the day, especially in the dark phases. Finally, we developed a feedback-loop algorithm to implement a place preference test based on the flies' innate aversion to blue light and preference for green light. We show that both white-eyed and red-eyed wild-type flies were able to learn to avoid the blue-illuminated zones.

Conclusions: Our results demonstrate the versatility of DISCO for a range of protocols, indicating that this platform can be used in a variety of ways to study light-dependent behaviours in flies.

Mechanisms of homeostatic plasticity promote compensatory changes of cellular excitability in response to chronic changes in the network activity. This type of plasticity is essential for the maintenance of brain circuits and is involved in the regulation of neural regeneration and the progress of neurodegenerative disorders. One of the most studied homeostatic processes is synaptic scaling, where global synaptic adjustments take place to restore the neuronal firing rate to a physiological range by the modulation of synaptic receptors, neurotransmitters, and morphology. However, despite the comprehensive literature on the electrophysiological properties of homeostatic scaling, less is known about the structural adjustments that occur in the synapses and dendritic tree. In this study, we performed a meta-analysis of articles investigating the effects of chronic network excitation (synaptic downscaling) or inhibition (synaptic upscaling) on the dendritic spine density of neurons. Our results indicate that spine density is consistently reduced after protocols that induce synaptic scaling, independent of the intervention type. Then, we discuss the implication of our findings to the current knowledge on the morphological changes induced by homeostatic plasticity.

The underlying mechanisms for statin-induced myopathy (SIM) are still equivocal. In this study, we employ Drosophila melanogaster to dissect possible underlying mechanisms for SIM. We observe that chronic fluvastatin treatment causes reduced general locomotion activity and climbing ability. In addition, transmission microscopy of dissected skeletal muscles of fluvastatin-treated flies reveals strong myofibrillar damage, including increased sarcomere lengths and Z-line streaming, which are reminiscent of myopathy, along with fragmented mitochondria of larger sizes, most of which are round-like shapes. Furthermore, chronic fluvastatin treatment is associated with impaired lipid metabolism and insulin signalling. Mechanistically, knockdown of the statin-target Hmgcr in the skeletal muscles recapitulates fluvastatin-induced mitochondrial phenotypes and lowered general locomotion activity; however, it was not sufficient to alter sarcomere length or elicit myofibrillar damage compared to controls or fluvastatin treatment. Moreover, we found that fluvastatin treatment was associated with reduced expression of the skeletal muscle chloride channel, C1C-a (Drosophila homolog of CLCN1), while selective knockdown of skeletal muscle C1C-a also recapitulated fluvastatin-induced myofibril damage and increased sarcomere lengths. Surprisingly, exercising fluvastatin-treated flies restored C1C-a expression and normalized sarcomere lengths, suggesting that fluvastatin-induced myofibrillar phenotypes could be linked to lowered C1C-a expression. Taken together, these results may indicate the potential role of C1C-a inhibition in statinassociated muscular phenotypes. This study underlines the importance of Drosophila melanogaster as a powerful model system for elucidating the locomotion and muscular phenotypes, promoting a better understanding of the molecular mechanisms underlying SIM.

The statin drug target, 3-hydroxy-3-methylglutaryl-CoA reductase (HMGCR), is strongly linked to body mass index (BMI), yet how HMGCR influences BMI is not understood. In mammals, studies of peripheral HMGCR have not clearly identified a role in BMI maintenance and, despite considerable central nervous system expression, a function for central HMGCR has not been determined. Similar to mammals, Hmgcr is highly expressed in the Drosophila melanogaster brain. Therefore, genetic and pharmacological studies were performed to identify how central Hmgcr regulates Drosophila energy metabolism and feeding behavior. We found that inhibiting Hmgcr, in insulin-producing cells of the Drosophila pars intercerebralis (PI), the fly hypothalamic equivalent, significantly reduces the expression of insulin-like peptides, severely decreasing insulin signaling. In fact, reducing Hmgcr expression throughout development causes decreased body size, increased lipid storage, hyperglycemia, and hyperphagia. Furthermore, the Hmgcr induced hyperphagia phenotype requires a conserved insulin-regulated alpha-glucosidase, target of brain insulin (tobi). In rats and mice, acute inhibition of hypothalamic Hmgcr activity stimulates food intake. This study presents evidence of how central Hmgcr regulation of metabolism and food intake could influence BMI.

In vivo optogenetic strategies have been fundamental for the investigation of how neural circuits relate to behavior. While short-term experimental procedures are typically used in such studies, chronic stimulation during behavioral sessions has been largely unexplored. Here we describe a protocol for long-term optogenetic modulation of neuronal populations in freely moving animals.