Biology subjects

Chiacchierini, G.

Publications and source records attributed to Chiacchierini, G..

6 recordsLinked to original sources

bioRxiv2026

A novel behavioral paradigm to model hypermemory-like features in rats

Episodic memory is essential to everyday life and personal identity. However, its dysfunctions can profoundly affect mental health, and translational methods for investigating them in animals remain limited. Most rodent paradigms focus on memory deficits, whereas few tools model abnormally enhanced and persistent memories. Here, we developed a behavioral paradigm to induce hypermemory-like features in adult male and female rats using a version of object recognition (OR) and object location (OL) tasks specifically modified to mimic the rumination-like component of hypermemory. During the odor-context association training, rats explored two identical objects in the presence of a cinnamon scent. Over the following 6 h, they received 12 brief re-exposures in their home cage to either the cinnamon odor or an odor-free stimulus. By repeatedly reactivating the memory trace, these re-exposures promoted its hyperconsolidation without re-exposing animals to the original context or objects. Twenty-four hours later, memory was assessed under odor-free conditions. Odor re-exposure selectively enhanced OL memory in rats of both sexes, whereas OR memory remained unaffected. The procedure did not alter total object exploration or locomotor activity. Enhanced spatial memory was also accompanied by increased c-Fos expression in the ventral hippocampus in both sexes. Our protocol recapitulates key features observed in individuals with hyperfunctional episodic memory: continuous memory reactivation and rumination which may contribute to the excessive strengthening and persistence of specific memories. This simple and reproducible paradigm provides a novel translational tool for investigating the behavioral and neurobiological mechanisms underlying memory hyperconsolidation and maladaptive memory persistence.

neuroscience↗

bioRxiv2025

Dietary protein restriction in rats leads to a rapid within-session preference for protein

Evolution has provided species with adaptive behavioural mechanisms that guarantee tight dietary protein regulation. However, an unsolved question is whether the well-established preference for protein-containing food manifested during states of protein restriction is innate or learned. Here, we tackled this problem by maintaining male rats on either a low-protein diet (5% protein, protein-restricted) or a control diet (22% protein, non-restricted) for 9-12 days, and then offered them two novel foods, a protein-containing solution (4% casein) and a carbohydrate-containing solution (4% maltodextrin) during a daily 60-minute free-choice test, repeated for 5 consecutive days. We assessed both the total and cumulative intake of each solution throughout each test, as well as the microstructure of licking behaviour as an index of the solutions palatability. In a second experiment, we exposed a different cohort of rats, before any behavioural test, to the same protein source (i.e., casein) that they would encounter during the free-choice tests, to assess whether familiarity with casein would drive subsequent casein intake even in non-restricted rats. We found that dietary protein restriction leads to a rapid preference (within 16 minutes of first exposure) for a casein-rich solution, and this preference is persistent over subsequent exposures. Increased palatability of protein during initial exposure correlated with protein preference in the restricted rats. Moreover, familiarity with casein did not lead to protein preference in non-restricted rats. This study demonstrates that, when in need of protein, protein preference is a rapid adaptation that requires minimal experience of protein. HighlightsO_LIProtein-restricted rats show a rapid preference for protein over carbohydrate C_LIO_LIThe preference emerges within 5 minutes of exposure to solutions C_LIO_LIIncreased palatability of casein is partially related to preference C_LIO_LIExposure to casein without protein restriction does not lead to preference C_LI

animal behavior and cognition↗

bioRxiv2022

Incertohypothalamic A13 dopaminergic neurons are involved in fine forelimb movements but not reward

Tyrosine hydroxylase (TH)-containing neurons of the dopamine (DA) cell group A13 are well-positioned to impact known dopamine-related functions since their descending projections innervate target regions that regulate vigilance, sensorimotor integration and execution. Despite this known connectivity little is known regarding the functionality of A13-DA circuits. Using TH-specific loss-of-function methodology and techniques to monitor population activity in transgenic rats in vivo we investigated the contribution of A13-DA neurons in reward and movement-related actions. Our work demonstrates a role for A13-DA neurons in grasping and handling of objects that is independent from reward. A13-DA neurons respond strongly when animals grab and manipulate food items while their inactivation or degeneration prevents animals from successfully doing so - a deficit partially attributed to a reduction in grip strength. In contrast, there was no relation between A13-DA activity and food-seeking behavior when animals were tested on a reward-based task that did not include a reaching/grasping response. Moreover, motivation for food was unaffected as goal-directed behavior for food items was in general intact following A13 neuronal inactivation/degeneration. These results demonstrate a functional role for A13-DA neurons in prehensile actions that are uncoupled from reward and as such position A13-DA neurons into the functional framework regarding centrally-located DA populations and their ability to coordinate movement.

neuroscience↗

bioRxiv2022

Restriction of dietary protein in rats increases progressive-ratio motivation for protein

Low-protein diets can impact food intake and appetite, but it is not known if motivation for food is changed. In the present study, we used an operant behavioral task - the progressive ratio test - to assess whether motivation for different foods was affected when rats were maintained on a protein-restricted diet (REST, 5% protein diet) compared to non-restricted control rats (CON, 18% protein). Rats were tested either with nutritionally-balanced pellets (18.7% protein, Experiment 1) or protein-rich pellets (35% protein, Experiment 2) as reinforcers. Protein restriction increased breakpoint for protein-rich pellets, relative to CON rats, whereas no difference in breakpoint for nutritionally-balanced pellets was observed between groups. When given free access to either nutritionally-balanced pellets or protein-rich pellets, REST and CON rats did not differ in their intake. We also tested whether a previous history of protein restriction might affect present motivation for different types of food, by assessing breakpoint of previously REST animals that were subsequently put on standard maintenance chow (protein-repleted rats, REPL, Experiment 2). REPL rats did not show increased breakpoint, relative to their initial encounter with protein-rich pellets while they were protein-restricted. This study demonstrates that restriction of dietary protein induces a selective increased motivation for protein-rich food, a behavior that disappears once rats are not in need of protein.

neuroscience↗

bioRxiv2021

Predictive and motivational factors influencing anticipatory contrast: A comparison of contextual and gustatory predictors in food restricted and free-fed rats

In anticipation of palatable food, rats can learn to restrict consumption of a less rewarding food type resulting in a binge on the preferred food when it is made available. This construct is known as anticipatory negative contrast (ANC) and can help elucidate the processes that underlie binge-like behavior as well as self-control in rodent motivation models. In the current investigation we aimed to shed light on the ability of distinct predictors of a preferred food choice to generate contrast effects and the motivational processes that underlie this behavior. Using a novel set of rewarding solutions, we directly compared contextual and gustatory ANC predictors in both food restricted and free-fed Sprague-Dawley rats. Our results indicate that, despite being food restricted, rats are selective in their eating behavior and show strong contextually-driven ANC and do so after fewer training sessions than free-fed animals. These differences mirrored changes in palatability for the less preferred solution across the different sessions as measured by lick microstructure analysis. Moreover, in contrast to previous research, gustatory cues in both food restricted and free-fed rats were sufficient for ANC to develop although this flavor-driven ANC did not relate to a corresponding change in lick patterning. These differences in the lick microstructure between context- and flavor-driven ANC indicate that the motivational processes underlying ANC generated by the two predictor types are distinct.

animal behavior and cognition↗

bioRxiv2019

Protein appetite drives neural activity in the ventral tegmental area

Control of protein intake is essential for numerous biological processes as several amino acids cannot be synthesized de novo, however, its neurobiological substrates are still poorly understood. In the present study, we combined in vivo fiber photometry with nutrient-conditioned flavor in a rat model of protein appetite to record neuronal activity in the ventral tegmental area (VTA), a central brain region for the control of food-related processes. In adult male rats, protein restriction increased preference for casein (protein) over maltodextrin (carbohydrate). Moreover, protein consumption was associated with a greater VTA response relative to carbohydrate. After initial nutrient preference, a switch from a normal balanced diet to protein restriction induced rapid development of protein preference but required extensive exposure to macronutrient solutions to induce greater VTA responses to casein. Furthermore, prior protein restriction induced long-lasting food preference and VTA responses. This study reveals that VTA circuits are involved in protein appetite in times of need, a crucial process for all animals to acquire an adequate amount of protein in their diet. Significance StatementAcquiring insufficient protein in ones diet has severe consequences for health and ultimately will lead to death. In addition, a low level of dietary protein has been proposed as a driver of obesity as it can leverage up intake of fat and carbohydrate. However, much remains unknown about the role of the brain in ensuring adequate intake of protein. Here, we show that in a state of protein restriction a key node in brain reward circuitry, the ventral tegmental area, is activated more strongly during consumption of protein than carbohydrate. Moreover, although rats behavior changed to reflect new protein status, patterns of neural activity were more persistent and only loosely linked to protein status.

neuroscience↗