Changes in reward-induced neural activity upon Cafeteria Diet consumption.

Excessive consumption of highly palatable foods rich in sugar and fat, often referred to as "junk" or "fast" foods, plays a central role in the development of obesity. The highly palatable characteristics of these foods activate hedonic and motivational mechanisms to promote food-seeking behavior and overeating, which is largely regulated by the brain reward system. Excessive junk food consumption can alter the functioning of this reward system, but exact mechanisms of these changes are still largely unknown. This study investigated whether long-term junk food consumption, in the form of Cafeteria (CAF) diet, can alter the reward system in adult, female Long-Evans rats, and whether different regimes of CAF diet influence the extent of these changes. To this end, rats were exposed to a 6-week diet with either standard chow, or ad libitum daily access to CAF diet, 30 % restricted but daily access to CAF diet, or one-day-a-week (intermittent) ad libitum access to CAF diet, after which c-Fos expression in the Nucleus Accumbens (NAc), Prefrontal Cortex (PFC), and Ventral Tegmental Area (VTA) following consumption of a CAF reward of choice was examined. We found that all CAF diet regimes decreased c-Fos expression in the NAc-shell when presented with a CAF reward, while no changes in c-Fos expression upon the different diet regimes were found in the PFC, and possibly the VTA. Our data suggests that long-term junk food exposure can affect the brain reward system, resulting in an attenuated activity of the NAc-shell.

Macroautophagic process was differentially modulated by long-term moderate exercise in rat brain and peripheral tissues.

The autophagic process is a lysosomal degradation pathway, which is activated during stress conditions, such as starvation or exercise. Regular exercise has beneficial effects on human health, including neuroprotection. However, the cellular mechanisms underlying these effects are incompletely understood. Endurance and a single bout of exercise induce autophagy not only in brain but also in peripheral tissues. However, little is known whether autophagy could be modulated in brain and peripheral tissues by long-term moderate exercise. Here, we examined the effects on macroautophagy process of long-term moderate treadmill training (36 weeks) in adult rats both in brain (hippocampus and cerebral cortex) and peripheral tissues (skeletal muscle, liver and heart). We assessed mTOR activation and the autophagic proteins Beclin 1, p62, LC3B (LC3B-II/LC3B-I ratio) and the lysosomal protein LAMP1, as well as the ubiquitinated proteins. Our results showed in the cortex of exercised rats an inactivation of mTOR, greater autophagy flux (increased LC3-II/LC3-I ratio and reduced p62) besides increased LAMP1. Related with these effects a reduction in the ubiquitinated proteins was observed. No significant changes in the autophagic pathway were found either in hippocampus or in skeletal and cardiac muscle by exercise. Only in the liver of exercised rats mTOR phosphorylation and p62 levels increased, which could be related with beneficial metabolic effects in this organ induced by exercise. Thus, our findings suggest that long-term moderate exercise induces autophagy specifically in the cortex.

Wnt pathway regulation by long-term moderate exercise in rat hippocampus.

An active lifestyle involving regular exercise reduces the deleterious effects of the aging process. At the cerebral level, both synaptic plasticity and neurogenesis are modulated by exercise, although the molecular mechanisms underlying these effects are not clearly understood. In the mature nervous system, the canonical Wnt (Wnt/ß-catenin) signaling pathway is implicated in neuroprotection and synaptic plasticity. Here, we examined whether the Wnt pathway could be modulated in adult male rat hippocampus by long-term moderate exercise (treadmill running) or enrichment (handling/environmental stimulation). Sedentary animals showed higher protein levels of the Wnt antagonist, Dkk-1, the lowest levels being found in the exercised group. Although there was no evidence of any changes in activation of the LRP6 receptor, the total levels of LRP6 were higher in exercised and enriched animals. Analysis of some of the components implicated in the phosphorylation of ß-catenin, which leads ultimately to its proteasomal degradation, revealed higher levels and activation of Axin1 and GSK-3α/ß respectively in sedentary animals. However neither different phosphorylated forms nor total ß-catenin protein levels differed between the experimental groups. Higher protein levels of Axin2 and the antiapoptotic protein, Bcl-2, were found with exercise and handling, whereas the proapototic, Bax, was unaffected. Thus, our results suggest activation of the Wnt pathway not only with moderate exercise, but also with the handling of the animals.

High tracking of apolipoprotein B levels from the prepubertal age to adolescence in Spanish children.

AIM: To assess tracking of lipid and apolipoproteins from the prepubertal age (baseline, 6-8 years old) to adolescence (follow-up, 13-16 years old) in Spanish children. METHODS: The sample population included 385 healthy children (179 boys and 206 girls). Tracking was estimated by correlations between baseline and follow-up levels, multiple regression models in which the follow-up lipid was the dependent variable and analysing the percentage of individuals who remained in the same lipid levels status from prepubertal age to adolescence. RESULTS: Correlations between baseline and follow-up levels for low density lipoprotein (LDL)-cholesterol and apolipoprotein B (apo B) were stronger in boys and for high density lipoprotein-cholesterol and apo A-I stronger in girls. Regression analyses showed that, after adjusting by body mass index (BMI), baseline LDL-cholesterol and apo B levels explain 23% and 39% of the variation of follow-up LDL-cholesterol and apo B levels, respectively, in boys and 13% and 22%, respectively, in girls. The strength of tracking for LDL-cholesterol and apo B was 79% and 89%, respectively, in boys and 72% and 82%, respectively, in girls. CONCLUSION: Apolipoprotein B showed the strongest tracking in both sexes, stronger than for LDL-cholesterol, which supports the importance of determining apo B levels as a marker of dyslipidaemia in children.

Long-term physical exercise induces changes in sirtuin 1 pathway and oxidative parameters in adult rat tissues.

The protein deacetylase, sirtuin 1, is suggested as a master regulator of exercise-induced beneficial effects. Sirtuin 1 modulates mitochondrial biogenesis, primarily via its ability to deacetylate and activate proliferator-activated receptor-γ coactivator-1α (PGC-1α), interacting with AMPK kinase. Redox cell status can also influence this regulatory axis and together they form an important convergence point in hormesis during the aging process. Here, we tested whether treadmill training (36weeks), as a paradigm of long-term moderate exercise, modifies the AMPK-sirtuin 1-PGC-1α axis and redox balance in rat gastrocnemius muscle, liver and heart. Physical activity induced increases in sirtuin 1 protein levels in all the aged rat tissues studied, as well as total PGC-1α levels. However, no changes in AMPK activation or significant differences in mitochondrial biogenesis (by measuring electron transport chain protein content) were found after exercise training. Parallel to these changes, we observed an improvement of oxidative stress defenses, mainly in muscle, with modification of the antioxidant enzyme machinery resulting in a reduction in lipid peroxidation and protein carbonylation. Thus, we demonstrate that moderate long-term exercise promotes tissue adaptations, increasing muscle, liver and heart sirtuin 1 protein content and activity and increasing PGC-1α protein expression. However, AMPK activation or mitochondrial biogenesis is not modified, but it cannot be discarded that its participation in the adaptive mechanism which prevents the development of the deleterious effects of age.

Long-term treadmill exercise induces neuroprotective molecular changes in rat brain.

Exercise enhances general health. However, its effects on neurodegeneration are controversial, and the molecular pathways in the brain involved in this enhancement are poorly understood. Here, we examined the effect of long-term moderate treadmill training on adult male rat cortex and hippocampus to identify the cellular mechanisms behind the effects of exercise. We compared three animal groups: exercised (30 min/day, 12 m/min, 5 days/wk, 36 wk), handled but nonexercised (treadmill handling procedure, 0 m/min), and sedentary (nonhandled and nonexercised). Moderate long-term exercise induced an increase in IGF-1 levels and also in energy parameters, such as PGC-1α and the OXPHOS system. Moreover, the sirtuin 1 pathway was activated in both the exercised and nonexercised groups but not in sedentary rats. This induction could be a consequence of exercise as well as the handling procedure. To determine whether the long-term moderate treadmill training had neuroprotective effects, we studied tau hyperphosphorylation and GSK3ß activation. Our results showed reduced levels of phospho-tau and GSK3ß activation mainly in the hippocampus of the exercised animals. In conclusion, in our rodent model, exercise improved several major brain parameters, especially in the hippocampus. These improvements induced the upregulation of sirtuin 1, a protein that extends life, the stimulation of mitochondrial biogenesis, the activation of AMPK, and the prevention of signs of neurodegeneration. These findings are consistent with other reports showing that physical exercise has positive effects on hormesis.

New indices for quantification of the power spectrum of heart rate variability time series without the need of any frequency band definition.

This paper presents a new family of indices for the frequency domain analysis of heart rate variability time series that do not need any frequency band definition. After proper detrending of the time series, a cumulated power spectrum is obtained and frequencies that contain a certain percentage of the power below them are identified, so median frequency, bandwidth and a measure of the power spectrum asymmetry are proposed to complement or improve the classical spectral indices as the ratio of the powers of LF and HF bands (LF/HF). In normal conditions the median frequency provides similar information as the classical indices, while the bandwidth and asymmetry can be complementary measures of the physiological state of the tested subject. The proposed indices seem to be a good choice for tracking changes in the power spectrum in exercise stress, and they can guide in the determination of frequency band limits in other animal species.

Litter size affects emotionality in adult male rats.

The role of natural variations in pre-weaning litter size in rodent adult emotionality and the importance of maternal care as a possible mediating factor have been frequently neglected. To address these issues, maternal behaviour of Sprague-Dawley dams differing in natural number of pups was studied for the first seven postnatal days. Later, adult behaviour of representative male offspring was studied in the elevated plus-maze, the circular corridor, the dark-light box and the forced swimming test. Three groups of offspring were selected in function of the number of littermates: L<10 group (less than 10 pups per dam), L10-15 (between 10 and 15 pups per dam) and L>15 group (more than 15 pups per dam). L<10 litters showed a reduced habituation of activity across time in a circular corridor and as compared to L>15 litters, L<10 litters showed a lower activity during the first 5 min of exposure to the circular corridor. L<10 litters had also higher signs of anxiety in the elevated plus-maze, in comparison to the other two groups. In addition, L<10 litters showed in the forced swimming test reduced struggling and more mild swimming behavior than the other two groups. These abnormalities in L<10 litters are not explained by maternal behavior since they received individually more maternal care than L>15, as assessed by total licking-grooming observed during the whole observation period divided by number of pups. Although previous data from several laboratories have demonstrated that low maternal care is associated with heightened emotionality at adulthood, the present results suggest an important contribution of spontaneous litter size to adult emotional behavior that cannot be explained by concomitant changes in maternal care.

Enduring effects of environmental enrichment on novelty seeking, saccharin and ethanol intake in two rat lines (RHA/Verh and RLA/Verh) differing in incentive-seeking behavior.

The Roman high- and low-avoidance (RHA/Verh and RLA/Verh) rat lines represent, respectively, low emotional/anxious and high novelty seeker vs. high emotional/anxious and low novelty seeker profiles. In the present study, RLA/Verh and RHA/Verh rats, either reared in pairs from weaning (untreated) or reared in groups of 8-10 in an enriched environment until the age of 7 months, were tested for exploratory and novelty-seeking behavior in the hole board (including novel objects under the holes), as well as for their preference for saccharin-water and ethanol-water in a two-bottle free-choice paradigm. Testing started when rats were 20 months old in order to study the long-lasting effects of differential rearing. RHA/Verh rats explored more and showed greater preference for (and intake of) saccharin as well as for ethanol than RLA/Verh rats, thus confirming their validity as a rat model for sensation/reward seeking. Environmental enrichment (EE) increased head-dipping behavior (i.e., novelty seeking) in both rat lines, without affecting locomotor activity. EE treatment increased the preference for, and volume intake of, saccharin (especially at the higher concentrations tested) in the relatively low saccharin-preferring RLA/Verh rats, and also enhanced ethanol consumption in both rat lines. Thus, the results demonstrate consistent and enduring effects of EE on incentive-seeking behavior and further the analysis of how individual differential predispositions for the need of novelty and contact with (or consumption of) rewarding substances arise through either biological (genetic) or early environmental factors, or both.

Hyperalgesia, anxiety, and decreased hypoxic neuroprotection in mice lacking the adenosine A1 receptor.

Caffeine is believed to act by blocking adenosine A(1) and A(2A) receptors (A(1)R, A(2A)R), indicating that some A(1) receptors are tonically activated. We generated mice with a targeted disruption of the second coding exon of the A(1)R (A(1)R(-/-)). These animals bred and gained weight normally and had a normal heart rate, blood pressure, and body temperature. In most behavioral tests they were similar to A(1)R(+/+) mice, but A(1)R(-/-) mice showed signs of increased anxiety. Electrophysiological recordings from hippocampal slices revealed that both adenosine-mediated inhibition and theophylline-mediated augmentation of excitatory glutamatergic neurotransmission were abolished in A(1)R(-/-) mice. In A(1)R(+/-) mice the potency of adenosine was halved, as was the number of A(1)R. In A(1)R(-/-) mice, the analgesic effect of intrathecal adenosine was lost, and thermal hyperalgesia was observed, but the analgesic effect of morphine was intact. The decrease in neuronal activity upon hypoxia was reduced both in hippocampal slices and in brainstem, and functional recovery after hypoxia was attenuated. Thus A(1)Rs do not play an essential role during development, and although they significantly influence synaptic activity, they play a nonessential role in normal physiology. However, under pathophysiological conditions, including noxious stimulation and oxygen deficiency, they are important.

Transmembrane signaling through phospholipase C in cortical and hippocampal membranes of psychogenetically selected rat lines.

RATIONALE: One of the major pathways for neurotransmitter signaling involves phosphoinositide-specific and G-protein-dependent phospholipase C-beta (PLC-beta), which stimulates the formation of inositol 1,4,5-trisphosphate and diacylglycerol. Serotonergic and muscarinic-cholinergic signals in the brain are largely mediated through the hydrolysis of phosphoinositides by PLC. OBJECTIVES: The aim of the experiments reported here was to explore the potential differences in neurotransmitter receptor coupling to PLC in Roman high-avoidance (RHA)/Verh and Roman low-avoidance (RLA)/Verh rats, by examining the changes in agonist (carbachol, 5-methyltryptamine)-stimulated phosphoinositide hydrolysis in hippocampal and cortical membranes derived from the two rat lines. METHODS: To investigate changes in receptor and G-protein coupling to PLC in the brains of these two psychogenetically selected rat lines, which differ in their emotional profiles/learning abilities, we examined GTPgammaS-, agonist (carbachol, 5-methyltryptamine)-, and calcium-stimulated phosphoinositide hydrolysis in cortical and hippocampal membranes of RHA/Verh and RLA/Verh rats. RESULTS: The results indicated that calcium-induced increase in PLC activity was larger in the cortex and hippocampus of RHA/Ver rats, as compared to their RLA/Verh counterparts. Conversely, GTPgammaS- and agonist-induced PLC activity was less pronounced in the hippocampus of RHA/Verh with respect to RLA/Verh rats. Western blot analysis showed no significant differences in the relative values of the G-proteins alphaq/11 and betagamma subunits between both groups of rats in any brain region. However, the levels of PLC-beta1, PLC-beta3, and PLC-beta4 were significantly lower in the hippocampus of RHA/Verh than in RLA/Verh rats. CONCLUSIONS: It is concluded that the hippocampus of RHA/Verh rats has severe deficiencies in PLC activity stimulated by guanine nucleotides and agonists, which are specifically related to a lower level of expression of the PLC-beta type isozymes, a fact that may account for the differential behavioral phenotype observed in these psychogenetically selected rat lines.

Differential effects of cohort removal stress on the acoustic startle response of the Roman/Verh rat strains.

Male and female rats of the inbred Roman/Verh strains, which have been psychogenetically selected and bred for good (RHA-I/Verh) and extremely poor (RLA-I/Verh) two-way avoidance acquisition, were evaluated in an acoustic startle response test. One half of the rats of each strain and sex were previously subjected to 30 min of isolation by removal of their cage partners ("cohort removal"). During the testing session each animal received 40 acoustic stimuli at interstimulus intervals of 30 seconds. The hyperemotional RLA-I/Verh rats (especially the males) showed stronger acoustic startle responses than did their RHA-I/Verh counterparts. Startle amplitudes of the RLA-I/Verh males were further enhanced by the stress of 30 min isolation, whereas cohort removal did not significantly affect startle response amplitudes in RHA-I/Verh rats of either sex or in females of the RLA-I/Verh strain.

Inbred Roman high- and low-avoidance rats: differences in anxiety, novelty-seeking, and shuttlebox behaviors.

In the present study, male inbred animals (from the 10th generation of an inbreeding program that has been carried out in parallel to that of the outbred Roman high- and low-avoidance rat lines), were compared for emotionality in different testing situations, exploratory behavior in the holeboard and two-way, active-avoidance acquisition. Compared to the inbred Roman high-avoidance (RHA-I/Verh) rats, inbred Roman low-avoidance (RLA-I-Verh) rats showed higher emotionality in the open field (reduced distance travelled and number of rearings, and increased self-grooming behavior), in the elevated plus-maze test (increased number of total and open-arm entries, reduced distance travelled in the open arms, and increased self-grooming behavior), and during the habituation period in the shuttle box (decreased number of crossings, increased self-grooming behavior and defecations). Results from the hyponeophagia test were not conclusive, probably due to the test-dependent hyperactivity shown by RHA-I/Verh rats. In the holeboard apparatus, RHA-I/Verh rats explored more than RLA-I/Verh rats, especially when novel objects were located beneath the holes. Finally, RHA-I/Verh animals rapidly acquired active, two-way (shuttlebox) avoidance, whereas RLA-I/Verh animals required four 50-trial sessions to achieve an assymptotic level of 30-40% avoidance. Thus, the behavioral patterns of the Roman inbred strains were very similar to those previously reported for the RHA/Verh outbred lines. Differences in locomotor activity, exploratory, and self-grooming behavior were actually greater between the inbred strains than between the outbred lines. Differences in defecation, however, although still significant, were not so pronounced as those noted previously at this laboratory with the outbred lines.

Long-term behavioural and neuroendocrine changes in Roman high-(RHA/Verh) and low-(RLA-Verh) avoidance rats following neonatal handling.

Roman high-(RHA/Verh) and low-(RLA/Verh) avoidance rats, originally selected and bred for rapid vs poor acquisition of a two-way active avoidance response, differ in emotional reactivity and coping style. These differences are associated with particular neuroendocrine and neurochemical characteristics. New data are presented here to show that the behavioural changes specifically induced by neonatal handling, i.e. decreased emotional reactivity, are associated with marked changes in the neuroendocrine responses of (hyperemotional) RLA/Verh rats to a novel environment. Eight months after neonatal handling, self-grooming behaviour, a reliable marker of emotional reactivity in this line of rats, was significantly decreased in RLA/Verh rats. Defecation scores were also significantly reduced in both lines. Moreover, there was a significant reduction in prolactin and corticosterone release following exposure to a novel environment in neonatally-handled RLA/Verh rats as compared to control, non-handled rats. No effects on prolactin and corticosterone release were observed in RHA/Verh rats. There was also no apparent effect of neonatal handling on coping style i.e. RLA/Verh rats did not increase their spontaneous exploration of novel environments. Thus, the phenotypic expression of basic traits of (high) neuroendocrine/emotional reactivity was specifically modulated by neonatal handling in RLA/Verh rats, whereas both the (hypoemotional) RHA/Verh rats as well as coping style in both lines remained unaffected. Changes in emotional reactivity were still apparent at 12 months of age when rats from the same groups were tested for hyponeophagia. These results suggest that psychogenetically selected lines such as RHA/RLA rats are suitable animal models to investigate interactions between genes and the environment in determining individual sensitivity to stress and coping styles, as well as potential vulnerability (or resistance) to the development of maladaptive syndromes similar to anxiety and mood disorders in humans.

Pharmacological properties of the GABA(A) receptor complex from brain regions of (hypoemotional) Roman high- and (hyperemotional) low-avoidance rats.

The pharmacological properties of benzodiazepine binding sites of the gamma-aminobutyric acid (GABA)A receptor complex from cortical, hippocampal and cerebellar membranes of Roman high-avoidance (RHA/Verh) and Roman low-avoidance (RLH/Verh) rats were investigated. No major differences between the two lines were found in the binding parameters of [3H]flunitrazepam (a non-selective agonist). [3 H]zolpidem (a Type I selective agonist) or [3 H]ethyl 8-azido-6-dihydro-5-methyl-6-oxo-4H-imidazol[1,5-a]-[1,4]benzodiazepine- 3-carboxylate (Ro15-4513) (a partial inverse agonist). Neither the Kd values nor the Bmax for these ligands differed between RHA/Verh and RLA/Verh rats in any of the brain regions studied. As a result, the proportion of Type I binding sites in cortical and hippocampal membranes of RHA/Verh and RLA/Verh rats or the 'diazepam-sensitive' and the 'diazepam-insensitive' binding sites in cerebellar membranes, calculated from the [3H]flunitrazepam and [3H]zolpidem maximal binding sites or from [3H]Ro15-4513 binding (in the absence or in presence of diazepam), respectively, was also similar. Furthermore, there were no differences between the two rat lines in the allosteric interactions between GABA and the benzodiazepine binding sites (labeled with [3H]flunitrazepam) in all three areas tested or the Type I binding sites (labeled with [3H]zolpidem) in the hippocampus. In contrast, RLA/Verh rats showed a significant reduction in the allosteric interactions between GABA and [3H]zolpidem binding sites in the cortex. As a whole, these results indicate the absence of generalized between-line differences in the GABA(A) receptor complex showing, at the same time, the existence of some specific differences in allosterism within the GABA(A) complex. These differences may contribute to the divergent emotional responses which characterize the RHA/Verh and RLA/Verh rat lines.

Impaired short- and long-term memory in Ts65Dn mice, a model for Down syndrome.

Ts65Dn (TS), control littermates (CO) and Swiss (SW) male mice were tested in the elevated plus-maze and in the Morris water maze (MWM) for memory evaluation. In the plus-maze, each mouse was placed at the end of an open arm and initial freezing and the time to enter into an enclosed arm (transfer latency) were measured. SW mice decreased both measures over repeated trials, whereas no decrease of freezing was observed in CO mice, thus suggesting increased emotionality in this group. Compared to CO mice, TS mice showed less initial freezing, shorter transfer latencies, and spent less time in enclosed arms, suggesting a reduced ability to habituate or to inhibit behaviour. Animals were also submitted to a learning-set paradigm consisting of reaching a new platform position each day in the MWM. Two training phases (separated by a resting period of 6 weeks), each including eight acquisition and four cued sessions, were performed (each session consisting of four pairs of trials). CO and SW mice already reached an asymptotic performance by the second day of the first phase whereas TS mice did not achieve that level until the second training phase. The progression over trials indicated that CO and SW animals learned the new platform position between trials 1 and 2 of each session, whereas TS animals failed to do it and had more difficulties to find the platform when it was placed in the centre of the pool as compared to the other positions (SW, NE, E). The results suggest that TS mice show working memory impairments in addition to long-term memory deficits, although extensive training appeared to facilitate TS mice to achieve a level of performance similar to their control littermates. This represents another aspect of the cognitive deficits shown by TS mice: a mouse model of the human Down syndrome.

Neonatal handling and environmental enrichment effects on emotionality, novelty/reward seeking, and age-related cognitive and hippocampal impairments: focus on the Roman rat lines.

Roman high- and low-avoidance (RHA/Verh and RLA/Verh) rats are selected and bred for extreme divergence in two-way active avoidance acquisition. In addition, compared to RLA/Verh rats, RHA/Verh rats are (behaviorally and physiologically) less anxious or reactive to stressors, show increased novelty (sensation)-seeking behavior as well as a higher preference for rewarding substances, and are usually less efficient in learning tasks not involving shock administration. The present article reviews evidence showing that neonatal handling and/or environmental enrichment leads to enduring effects (their magnitude frequently depending upon the rat line) on those behaviors. For example, it has been found that neonatal handling reduces most of the (behavioral and physiological) signs of emotionality/anxiety in RLA/Verh rats, while environmental enrichment increases their novelty seeking (also the case with RHA/Verh rats), saccharin and ethanol intake, and sensitivity to amphetamine. Finally, initial results (currently being further elaborated upon) support a preventive action of both environmental treatments on age-related impairments in learning a spatial, water maze task as well as on hippocampal neuronal atrophy.