Juan C. Brenes

University of Costa Rica | UCR · Instituto de Investigaciones Psicológicas (IIP)

In vulnerable consumers, the first drug exposure induces various neurobehavioral adaptations that may represent the starting point toward addiction. Elucidating the neuroplastic mechanisms underlying that first rewarding experience would contribute to understanding the transition from recreational to compulsive drug use. In a preclinical model with...

Introduction. The alarming increase in obesity both worldwide and in Costa Rica is mainly due to changes in the composition of the usual diet of the population. The goal of our research was to implement a feeding protocol formulated from ultra-processed and highly palatable foods (UPHP) consumed by the Costa Rican population and to evaluate the eff...

Introduction. Obesity is a multifactorial trait provoked by the interaction of biological, environmental, psychosocial, and socioeconomic factors. Proposal: The goal of the present review is to discuss the role of ultra-processed and highly palatable foods (UPHP) in the development of the obesity epidemic through an exploratory-descriptive review a...

Modern westernized diet is a major risk factor associated with the current obesity epidemic. To study the effects of dietary choices of Western societies, the cafeteria diet has been validated as a preclinical model of obesity. We aimed to investigate the behavioral and metabolic alterations induced by a cafeteria diet on gene expression and neurot...

Resumen Una dieta variada se asocia a una mayor probabilidad de incorporar micronutrientes esenciales. El índice de diversidad de dieta (IDD) es el indicador que mide esta variedad, mientras que el índice de calidad de dieta (ICD) determina cuánto de esa diversidad refleja la inclusión de alimentos saludables. El objetivo del estudio fue evaluar la...

The alarming increase in obesity both worldwide and in Costa Rica is mainly due to changes in the composition of the usual diet of the population. The goal of our research was to implement a feeding protocol formulated from ultra-processed and highly palatable foods (UPHP) consumed by the Costa Rican population and to evaluate the effects of the UP...

Obesity is a multifactorial trait provoked by the interaction of biological, environmental, psychosocial, and socioeconomic factors. Proposal: The goal of the present review is to discuss the role of ultra-processed and highly palatable foods (UPHP) in the development of the obesity epidemic through an exploratory-descriptive review and to present...

Following a varied diet is associated with a healthier diet and a greater likelihood of incorporating the necessary micronutrients. The dietary diversity index (DDI) is the indicator that measures this variety, while the diet quality index (DQI) determines how much of this diversity consists of the inclusion of healthy foods. The aim of the study w...

Alcohol consumption is a modifiable risk factor for non-communicable diseases. This study aimed to characterize alcohol consumers at the nutritional, anthropometric, and sociodemographic levels. Data from 9218 participants from Argentina, Brazil, Chile, Colombia, Costa Rica, Ecuador, Peru, and Venezuela participating in “Latin American Health and N...

Laboratory rats repeatedly exposed to an open field (OF) apparatus display increasingly high levels of groomingv–especially that characterized by long and complex sequences– which has been taken as an additional index ofvnovelty habituation. We hypothesized that disrupting such a learning process by administering an amnesic drug as the antimuscarin...

Poor health and diet quality are associated with living within a low socioeconomic status (SES). This study aimed to investigate the impact of SES on diet quality and body mass index in Latin America. Data from the “Latin American Health and Nutrition Study (ELANS)”, a multi-country, population-based study of 9218 participants, were used. Dietary i...

As drug addiction may result from pathological usurpations of learning and memory's neural mechanisms, we focused on the amphetamine-induced time-dependent neurochemical changes associated with neural plasticity. We used juvenile rats as the risk for drug abuse is higher during adolescence. Experiment 1 served to define the appropriate amphetamine...

Mounting evidence shows that physical activity, social interaction, and sensorimotor stimulation provided by environmental enrichment (EE) exert several neurobehavioral effects traditionally interpreted as enhancements relative to standard housing (SH) conditions. However, this evidence rather indicates that SH induces many deficits, which could be...

Within behavioral neuroscience, subjects used to be randomly assigned to the experimental groups based on the premise that interindividual variability will be homogeneously distributed. However, the equivalence offered by randomization diminishes in small samples, which is the case for most experiments in the field. In rodents, it is well-recognize...

Dietary diversity, an important component of diet quality, is associated with an increased probability of adequate micronutrient intake. Women of childbearing age (WCA) are particularly vulnerable to micronutrient inadequacy. The Minimum Dietary Diversity for Women (MDD-W) has been used widely as a proxy measurement of micronutrient adequacy. This...

We assessed the antidepressant-like effects of environmental enrichment (EE) and physical exercise (PE) compared with the selective serotonin reuptake inhibitor fluoxetine against the depression-related neurobehavioral alterations induced by postweaning social isolation (SI) in rats. After 1 month of SI, rats were submitted to PE (treadmill), EE, o...

To study how motivational factors modulate experience-dependent neurobehavioral plasticity, we modify a protocol of environmental enrichment (EE) in rats. We assumed that the benefits derived from EE might vary according to the level of incentive salience attributed to it. To enhance the rewarding properties of EE, access to the EE cage varied rand...

Grooming behaviour in rodents has been associated with emotional distress, especially in unfamiliar and aversive contexts. However, the biological function of grooming in such situations is still unclear. We hypothesised that particular grooming subtypes are differentially associated with the stress response. Here, we investigated the effects of an...

The chronic unpredictable stress (CUS) paradigm is extensively used in preclinical research. However, CUS exhibits translational inconsistencies, some of them resulting from the use of adult rodents, despite the evidence that vulnerability for many psychiatric disorders accumulates during early life. Here, we assessed the validity of the CUS model...

Habituation is a form of non associative learning characterized by the reduction of a given response after repeated or prolonged exposures to the eliciting stimuli. In rats, habituation is typically assessed by means of a single or repeated exposure to an unconditioned anxiety test such as the open field (OF). The OF consists of an open, illuminate...

In rats, environmental enrichment (EE) is a form of physical-social stimulation used for modeling the impact of optimal developmental conditions on animal’s phenotype. When implemented during early life, EE improves animal’s cognitive skills, reduces anxiety-like traits, and promotes different forms of brain plasticity. Conversely, young animals ra...

This study aimed to assess diet quality score (DQS), considering healthy and unhealthy foods and nutrients, and diet diversity score (DDS) as indicators of risk of noncommunicable diseases in eight Latin American countries, and to verify the possible differences considering country, sex, age, socioeconomic, and nutritional status. A multicenter hou...

In laboratory rats, naturally-occurring variations in maternal care have been used to study the neurobehavioral consequences of maternal nursing and to model the early-life adversity associated with many psychiatric disorders. This study aimed to determine the role of maternal care on behavior and monoamine concentrations at the prepubertal and you...

Grooming is a widespread behavior in the animal kingdom primarily geared towards the care of the body surface; nonetheless, other behavioral functions have been investigated and postulated. For example, rodents display high levels of grooming in contexts of potential threat, a fact usually interpreted as a sign of stress and anxiety. Conversely, ne...

In laboratory rats, one of the most used paradigms to assess habituation to novelty is the open-field test. Environmental enrichment has proved to be a reliable way to enhance open-field test habituation. Experiment 1, therefore, was designed to test whether grooming behaviour in the open-field test increases concomitantly with the habituation of e...

Habituation is the ability to passively reduce a response after repeated or prolonged exposures to a particular stimulus. From a cognitive perspective, habituation is a basic, information-gating process that contributes to filter out irrelevant information in order to focus cognitive sources on a specific goal. In higher order capabilities as in sp...

Introduction. St. John’s wort (Hypericum perforatum, HP) is one of the most used herbal medicines. Here we investigated the putative antidepressive- and anxiolytic-like effects of HP, by using a wellvalidated rat model of anxiety and depression based on chronic stress. Methods. To this purpose, subjects were either immobilized (INM) or randomly ex...

Habituation usually refers to as the decrease of a response after repeated or prolonged presentations of a given stimulus. This phenomenon has been observed along different life forms (e.g. amoeba, plants, rats, humans). In animals, habituation is considered as a non-associative learning process, which serves as a first-order attentional system fil...

Environmental Enrichment (EE) is a model to study the relationships between behavior and experience-dependent changes in the brain (Mora-Gallegos et al., 2015). Having access to an EE cage may be rewarding for rats and once EE is experienced, motivation to get enriched may gradually increase. Although the motivational properties of exercise have wi...

Environmental enrichment (EE) is one of the most used paradigms to model neurobehavioral consequences of environmental stimulation in rodents. Compared to standard housing, animals under EE are housed in larger and more complex cages with different social and non-social stimuli. The principle behind EE is to provide 1) greater levels of physical, s...

Ponencia presentada en el II Encuentro Académico de la Facultad de Medicina de la Universidad de Costa Rica.

The open field test (OFT) has been extensively used for assessing exploratory behavior, memory, and anxiety-related traits in rodents. Previous evidence suggests that early environmental enrichment (EE) reduces psychomotor reactivity to novelty in the OFT, as compared with animals reared in standard housing (SH). A detailed analysis of OFT activity...

Environmental enrichment (EE) exerts beneficial effects on brain plasticity, cognition, and anxiety/depression, leading to a brain that can counteract deficits underlying various brain disorders. Since the complexity of EE commonly used makes it difficult to identify causal aspects, we examined possible factors using a 2x2 design with social EE (2...

Reward-related stimuli come to acquire incentive salience through Pavlovian learning and become capable of controlling reward-oriented behaviors. Here, we examined individual differences in anticipatory activity elicited by reward-related cues as indicative of how animals attribute incentive salience to otherwise neutral stimuli. Since adult rats c...

Rats express affective states by visible behaviors (like approach or flight) and through different kinds of ultrasonic vocalizations (USV). 50-kHz calls are thought to reflect positive affective states since they occur during rewarding situations like social play or palatable food. However, the effects of voluntary exercise on USV have not been inv...

After experiencing a reward, the positive affective reactions it induces can become associated with its sensory properties and related cues. However, the manner in which such affective reward representations are expressed in animals remains unclear. Juvenile and adult rats communicate through ultrasonic vocalizations (USVs), which also serve as sit...

During Pavlovian incentive learning, the affective properties of rewards are thought to be transferred to their predicting cues. However, how rewards are represented emotionally in animals is widely unknown. This study sought to determine whether 50-kHz ultrasonic vocalizations (USVs) in rats may signal such a state of incentive motivation to natur...

Animal models aimed to mimic mania have in common the lack of genuine affective parameters. Although rodent amphetamine-induced hyperlocomotion is a frequently used behavioral model of mania, locomotor activity is a rather unspecific target for developing new pharmacological therapies, and does not necessarily constitute a cardinal symptom in bipol...

Electrical stimulation of midbrain tectum structures, particularly the dorsal periaqueductal gray (dPAG) and inferior colliculus (IC), produces defensive responses, such as freezing and escape behavior. Freezing also ensues after termination of dPAG stimulation (post-stimulation freezing). These defensive reaction responses are critically mediated...

Our previous work has shown that male Sprague-Dawley rats reared in social isolation, standard housing and environmental enrichment differ in their spontaneous open-field activity and in some neurobehavioral depressive-like parameters. Here, we extended this evidence by using a shorter postweaning rearing period (1 month) and including additional e...

This study examined the effect of fluoxetine, a selective serotonin (5-HT) reuptake inhibitor, on isolation-induced changes on sucrose consumption and preference, spontaneous open-field activity, forced swimming behavior, and on tissue levels of 5-HT and dopamine (DA) in hippocampus and ventral striatum (VS). Male Sprague-Dawley rats were reared in...

Little attention has been directed towards environmental control of sensitivity to natural reward and its possible relationship with other motivated behaviors, besides the well-known effects of environmental enrichment and social isolation on drug self-administration and locomotor sensitization to psychostimulants. Here, we investigate the effects...

In order to determine the effect of postnatal environments on some behavioral and neurochemical depressive-like parameters, male Sprague-Dawley rats were reared from weaning in either social isolation, standard laboratory conditions, or environmental enrichment. Open-field activity was assessed at postnatal days 37, 65, 93 and 107 and 1 h before th...

p style="text-align: justify;">Se probó la Escala de Adhesión al Tratamiento de la Diabetes Mellitus tipo II-versión III (EATDM-III©), la cual estaba compuesta por los factores apoyo familiar, organización y apoyo comunal, ejercicio físico, control médico, higiene y autocuidado, dieta y valoración de la condición física. La investigación se realizó...

The Adhesion to the Treatment of the Diabetes Mellitus type II (EATDM-III©) scale was proved, which was composed by the factors Familiar Support, Organization and Communal Support, Physical Exercise, Medical checkup, Hygiene and Self-Care, Diet and Valuation of the Physical Training Conditions. The investigation was made in public health centers of...

The Scale for Treatment Adherence in Type 2 Diabetes Mellitus version III (EATDMIII©) was tested. It was compounded by the following factors: Family Support, Organization and Community Support, Physical Exercise, Medical Control, Hygiene and SelfCare, Diet and Assessment of Physical Condition. The research was developed at Dr. Rafael Ángel Calderón...

Se probó la Escala de Adherencia al Tratamiento de la Diabetes Mellitus tipo II-versión III (EATDM-III©), la cual estaba compuesta por los factores Apoyo Familiar, la Organización y Apoyo Comunal, el Ejercicio Físico, el Control Médico, el Higiene y Autocuidado, la Dieta y la Valoración de la Condición Física. La investigación se realizó en el Hosp...

Developmental and social factors are known to play a crucial role in the pathogenesis of affective disorders. Although it has been demonstrated that early life aversive experiences can be a risk factor in the development of human depression, most of the investigation in animals that try to model depression do not include postnatal manipulations. Si...

La hipótesis que ha dominado el conocimiento de la depresión durante los últimos 50 años, la hipótesis de las monoaminas, está siendo desplazada por el desarrollo de otros modelos psicobiológicos. Uno de los modelos más importantes es el de la disfunción del eje hipotalámico – hipofisiario – suprarrenal (HHS), que relaciona los acontecimientos...