Low prepulse inhibition predicts lower social interaction, impaired spatial working memory, reference memory and cognitive flexibility in genetically heterogeneous rats.

The "Genetically Heterogeneous National Institutes of Health (NIHHS)" stock rat (hereafter HS) shows a wide phenotypic variation, as a result of having been derived from eight inbred rat strains. Thus, these rats may be a conceivable parallel model of a healthy human sample. In order to evaluate whether HS rats have face validity as an animal model of schizophrenia-relevant features, it should be demonstrated that they present behavioural traits that may model negative and cognitive symptoms of the disorder. Previous studies on HS rats have shown that prepulse inhibition (PPI, a measure of sensorimotor gating processes), which is impaired in schizophrenic patients, is correlated with their working memory performance. In this study, we evaluated whether low PPI in the HS stock rat predicts impairments of spatial working memory (SWM), spatial reference memory and cognitive flexibility in the Morris water maze (MWM) test, and we evaluated HS rats for social interaction (SI) in a social investigation task. HS rats were stratified into 2 different groups according to their PPI scores, i.e. low- and high-PPI. In the SI task, low-PPI rats showed decreased social behaviour compared to high-PPI rats. In addition, relative to high-PPI HS rats, the low-PPI group displayed poorer SWM performance, impaired cognitive flexibility (in a reversal task) and worsened long-term spatial memory. Such differential behaviours in social and cognitive paradigms provide evidence on the face validity of low-PPI HS rats as a model of negative-like and cognitive schizophrenia-relevant traits.

c-Fos expression after neonatal handling in social brain regions: Distinctive profile of RHA-rat schizophrenia model on a social preference test.

Neonatal handling (NH) is an environmental manipulation that induces long-lasting changes in behavioural, neuroendocrine, and neuroanatomical processes in rodents. We have previously reported that NH treatment increases social interaction preference in an animal model of schizophrenia-relevant features, the Roman high-avoidance (RHA) rats. The present study was aimed at evaluating whether the increase of social behaviour/preference due to NH treatment in RHA rats is associated with differences in c-Fos expression levels in some of the brain areas that integrate the "social brain". To this aim, we evaluated the performance of adult male rats from both Roman rat strains (RHA vs. RLA -Roman low-avoidance- rats), either untreated (control) or treated with NH (administered during the first 21 days of life) in a social interaction task. For the analyses of c-Fos activation untreated and NH-treated animals were divided into three different experimental conditions: undisturbed home cage controls (HC); rats exposed to the testing set-up context (CTX); and rats exposed to a social interaction (SI) test. It was found that, compared with their RLA counterparts, NH treatment increased social behaviour in RHA rats, and also specifically enhanced c-Fos expression in RHA rats tested for SI in some brain areas related to social behaviour, i.e. the infralimbic cortex (IL) and the medial posterodorsal amygdala (MePD) regions.

Increased thin-spine density in frontal cortex pyramidal neurons in a genetic rat model of schizophrenia-relevant features.

The cellular mechanisms altered during brain wiring leading to cognitive disturbances in neurodevelopmental disorders remain unknown. We have previously reported altered cortical expression of neurodevelopmentally regulated synaptic markers in a genetic animal model of schizophrenia-relevant behavioral features, the Roman-High Avoidance rat strain (RHA-I). To further explore this phenotype, we looked at dendritic spines in cortical pyramidal neurons, as changes in spine density and morphology are one of the main processes taking place during adolescence. An HSV-viral vector carrying green fluorescent protein (GFP) was injected into the frontal cortex (FC) of a group of 11 RHA-I and 12 Roman-Low Avoidance (RLA-I) male rats. GFP labeled dendrites from pyramidal cells were 3D reconstructed and number and types of spines quantified. We observed an increased spine density in the RHA-I, corresponding to a larger fraction of immature thin spines, with no differences in stubby and mushroom spines. Glia cells, parvalbumin (PV) and somatostatin (SST) interneurons and surrounding perineuronal net (PNN) density are known to participate in FC and pyramidal neuron dendritic spine maturation. We determined by stereological-based quantification a significantly higher number of GFAP-positive astrocytes in the FC of the RHA-I strain, with no difference in microglia (Iba1-positive cells). The number of inhibitory PV, SST interneurons or PNN density, on the contrary, was unchanged. Results support our belief that the RHA-I strain presents a more immature FC, with some structural features like those observed during adolescence, adding construct validity to this strain as a genetic behavioral model of neurodevelopmental disorders.

Cognitive and emotional alterations in young Alzheimer's disease (3xTgAD) mice: effects of neonatal handling stimulation and sexual dimorphism.

Alzheimer disease is the most common neurodegenerative disorder and cause of senile dementia. It is characterized by an accelerated memory loss, and alterations of mood, reason, judgment and language. The main neuropathological hallmarks of the disorder are ß-amyloid (ßA) plaques and neurofibrillary Tau tangles. The triple transgenic 3xTgAD mouse model develops ßA and Tau pathologies in a progressive manner which mimicks the pattern that takes place in the human brain with AD, and showing cognitive alterations characteristic of the disease. The present study intended to examine whether 3xTgAD mice of both sexes present cognitive, emotional and other behavioral alterations at the early age of 4 months, an age in which only some intraneuronal amyloid accumulation is found. Neonatal handling (H) is an early-life treatment known to produce profound and long-lasting behavioral and neurobiological effects in rodents, as well as improvements in cognitive functions. Therefore, we also aimed at evaluating the effects of H on the behavioral/cognitive profile of 4-month-old male and female 3xTgAD mice. The results indicate that, (1) 3xTgAD mice present spatial learning/memory deficits and emotional alterations already at the early age of 4 months, (2) there exists sexual dimorphism effects on several behavioral variables at this age, (3) neonatal handling exerts a preventive effect on some cognitive (spatial learning) and emotional alterations appearing in 3xTgAD mice already at early ages, and 4) H treatment appears to produce stronger positive effects in females than in males in several spatial learning measures and in the open field test.

Context-dependent differences in grooming behavior among the NIH heterogeneous stock and the Roman high- and low-avoidance rats.

Grooming occurs during/after stress and seems to accompany dearousal. Here, grooming was investigated under testing situations involving different levels of aversiveness, taking advantage of differences among three rat strains in fearfulness/anxiety. Inbred Roman High Avoidance (RHA-I) rats are less anxious/fearful than inbred Roman Low Avoidance (RLA-I). The outbred genetically heterogeneous stock of rats (NIH-HS), which resembles the RLA-I in many behavioral traits, was also studied. Adult male rats (RLA-I: n=9, RHA-I: n=10, NIH-HS: n=12) were observed for 30min in: a novel open-field, a novel hole-board and in the home-cage. They were also observed during two-way active avoidance training. Differences in grooming depended on test situation: (a) No differences were found in the home-cage. (b) While tested in a novel environment, RHA-I showed less grooming activity than the other rats. (c) After avoidance responses appeared, differences among the strains were opposite to the observed in novelty tests. Furthermore, results suggest that (i) grooming is mostly suppressed when assured aversive experience is under way; (ii) rostral grooming prevails when experience with aversive stimuli is unpredictable (novelty) or potential (avoidance training); (iii) body grooming increases for a period in novel environments. In general, our results support that grooming takes place during dearousal.

Regional adaptations in PSD-95, NGFI-A and secretogranin gene transcripts related to vulnerability to behavioral sensitization to amphetamine in the Roman rat strains.

Genetically selected for high or low two-way active avoidance, Roman high-avoidance (RHA) and Roman low-avoidance (RLA) rats differ in their central dopaminergic activity, sensation/novelty- and substance-seeking profiles. These animals are, therefore, well suited to identify anatomical and neurochemical concomitants of behavioral sensitization, a phenomenon linked to addictive liability. We submitted inbred RHA (RHA-I), inbred RLA (RLA-I) and Sprague-Dawley-OFA (SD-OFA) rats to a sensitization regimen with amphetamine and studied the behavioral response to an amphetamine challenge after a 2-week withdrawal period. The expression patterns of nerve growth factor inducible clone A (NGFI-A), secretogranin, post-synaptic density protein of 95 Kd (PSD-95), prodynorphin and proenkephalin mRNA were also analyzed using in situ hybridization, after the challenge with amphetamine. RHA-I rats showed stronger sensitization than SD-OFA rats. RLA-I rats did not show sensitization but were hyper-reactive to amphetamine. Expression of behavioral sensitization in RHA-I rats activated secretogranin and PSD-95 mRNA in the nucleus accumbens core. On the other hand, high induction of NGFI-A mRNA in the central amygdala was observed in RLA-I rats when they experienced amphetamine for the first time in the challenge. Our results reveal that 1) the acute locomotor response to amphetamine does not predict vulnerability to behavioral sensitization and 2) differences in vulnerability to sensitization may involve distinctive cellular adaptations at particular brain locations which may be related to addictive vulnerability.

Modeling behavioral and neuronal symptoms of Alzheimer's disease in mice: a role for intraneuronal amyloid.

The amyloid Abeta-peptide (Abeta) is suspected to play a critical role in the cascade leading to AD as the pathogen that causes neuronal and synaptic dysfunction and, eventually, cell death. Therefore, it has been the subject of a huge number of clinical and basic research studies on this disease. Abeta is typically found aggregated in extracellular amyloid plaques that occur in specific brain regions enriched in nAChRs in Alzheimer's disease (AD) and Down syndrome (DS) brains. Advances in the genetics of its familiar and sporadic forms, together with those in gene transfer technology, have provided valuable animal models that complement the traditional cholinergic approaches, although modeling the neuronal and behavioral deficits of AD in these models has been challenging. More recently, emerging evidence indicates that intraneuronal accumulation of Abeta may also contribute to the cascade of neurodegenerative events and strongly suggest that it is an early, pathological biomarker for the onset of AD and associated cognitive and other behavioral deficits. The present review covers these studies in humans, in in vitro and in transgenic models, also providing more evidence that adult 3xTg-AD mice harboring PS1M146V, APPSwe, tauP301L transgenes, and mimicking many critical hallmarks of AD, show cognitive deficits and other behavioral alterations at ages when overt neuropathology is not yet observed, but when intraneuronal Abeta, synaptic and cholinergic deficits can already be described.

Divergent anatomical pattern of D1 and D3 binding and dopamine- and cyclic AMP-regulated phosphoprotein of 32 kDa mRNA expression in the Roman rat strains: Implications for drug addiction.

Autoradiography analysis of D1, D2 and D3 dopamine receptors and in situ hybridization analysis of mRNA for dopamine and cAMP regulated phosphoprotein of 32 kDa (DARPP-32) were performed in brains of naïve Roman high avoidance (RHA) and Roman low avoidance (RLA) inbred rats. These strains, genetically selected for high (RHA) or extremely low (RLA) active avoidance acquisition in the two-way shuttle box, differ in indices of dopaminergic activity along with sensation/novelty and substance-seeking behavioral profiles. The present study shows no differences in D2 receptor binding between the two strains. In contrast, the D1 and D3 receptor binding in the nucleus accumbens was higher in RHA-I rats, whereas RLA-I rats show higher D3 binding in the Calleja islands. Together with previous evidence showing behavioral and presynaptic differences related to the dopamine system, the present results suggest a higher dopaminergic tone at the nucleus accumbens shell in RHA-I rats. Besides, the comparison of the expression pattern of DARPP-32 mRNA with that of dopamine receptor binding revealed a mismatch in some amygdala nuclei. In some cortical structures (prelimbic and cingulate cortices, the dentate gyrus) as well as in the central amygdala, RHA-I rats showed higher DARPP-32 mRNA expression than RLA-I rats. Hence, RHA-I and RLA-I rats may be a useful tool to identify dopamine-related mechanisms that predispose to drug and alcohol dependence.

El umbral de inhibición latente en las ratas romanas de alta evitación: ¿un modelo psicogenético de anomalías en el filtraje atencional? / Latent inhibition threshold in Roman high-avoidance rats: a psychogenetic model of abnormalities in attentional filter?

Introducción. Además de los modelos animales basados en la inducción de síntomas «psicóticos» mediante de fármacos psicoestimulantes, en la investigación sobre las alteraciones psicobiológicas de la esquizofrenia y sus tratamientos es cada vez más patente la necesidad de modelos que posean mayor validez de constructo, tales como líneas de animales que presenten espontáneamente singularidades asociadas a los trastornos psicóticos (p. ej., una mayor sensibilidad a los efectos de los psicoestimulantes o las anomalías cognitivas/atencionales típicas de los síndromes esquizofrénicos). Diversas evidencias experimentales indican que la cepa de ratas RHA (romanas de alta evitación) muestra un perfil neurobiológico y conductual consistente con tales requisitos.Métodos. Utilizando ratas RHA, en comparación con ratas Sprague-Dawley (SD) como un control estándar, se evaluó la expresión de inhibición latente (en una sesión de 100 ensayos de evitación activa en dos sentidos) en ambas cepas y en condiciones de umbral (con sólo 15 preexposiciones al estímulo condicionado).Resultados. Las ratas SD muestran en tales condiciones inhibición latente significativa en los 50 primeros ensayos y en el total de la sesión, fenómeno atencional que no aparece en la cepa RHA.Conclusiones. El déficit en inhibición latente en condiciones umbral, que mostraron los animales RHA, es compatible con la idea de que dicha cepa puede representar un modelo útil para el estudio de la vulnerabilidad a las alteraciones del espectro esquizofrénico. Una conclusión avalada por los datos que indican que los déficit en inhibición latente son una anomalía atencional característica de aquellas patologías

Introduction. Basic research devoted to the study of the psychobiological anomalies of schizophrenia, as well as of its treatments, has used animal models in which some psychotic-like symptoms are induced by administration of psychostimulant drugs. There is, however, a growing necessity of having animal models presenting better construct validity, i.e., animal lines spontaneously showing phenotypes associated to the psychotic spectrum (for instance, enhanced sensitivity to psychostimulants, or cognitive and attentional anomalies characteristic of schizophrenic disorders). Several lines of evidence suggest that the RHA (Roman high-avoidance) rat strain presents a neurobehavioral profile which is consistent with such goals. ;;Methods. RHA rats were compared to Sprague-Dawley (SD) rats (as a standard control strain) for the expression of latent inhibition (in a 100-trial session of two-way active avoidance) under threshold conditions (i.e., only 15 preexposures to the conditioned stimulus were administered). Results. Under such experimental conditions SD rats showed significant latent inhibition of the two-way active avoidance response (both during the first 50 trials and in the whole 100-trial session), while that attentional phenomenon did not appear in the RHA strain. Conclusions. The experimental results obtained here indicate that RHA rats display a deficit of latent inhibition at threshold conditions, an information processing (or attentional) anomaly which typically appears in schizophrenic patients. It is proposed that RHA rats might be an useful animal model for the study of vulnerability to some schizophrenic symptoms. This conclusion is supported by data that indicate that latent inhibition deficits are a characteristic attentional abnormality of these diseases

[Latent inhibition threshold in Roman high-avoidance rats: a psychogenetic model of abnormalities in attentional filter?]. / El umbral de inhibición latente en las ratas romanas de alta evitación: un modelo psicogenético de anomalías en el filtraje atencional?

INTRODUCTION: Basic research devoted to the study of the psychobiological anomalies of schizophrenia, as well as of its treatments, has used animal models in which some psychotic-like symptoms are induced by administration of psychostimulant drugs. There is, however, a growing necessity of having animal models presenting better construct validity, i.e., animal lines spontaneously showing phenotypes associated to the psychotic spectrum (for instance, enhanced sensitivity to psychostimulants, or cognitive and attentional anomalies characteristic of schizophrenic disorders). Several lines of evidence suggest that the RHA (Roman high-avoidance) rat strain presents a neurobehavioral profile which is consistent with such goals. METHODS: RHA rats were compared to Sprague-Dawley (SD) rats (as a standard control strain) for the expression of latent inhibition (in a 100-trial session of two-way active avoidance) under threshold conditions (i.e., only 15 preexposures to the conditioned stimulus were administered). RESULTS: Under such experimental conditions SD rats showed significant latent inhibition of the two-way active avoidance response (both during the first 50 trials and in the whole 100-trial session), while that attentional phenomenon did not appear in the RHA strain. CONCLUSIONS: The experimental results obtained here indicate that RHA rats display a deficit of latent inhibition at threshold conditions, an information processing (or attentional) anomaly which typically appears in schizophrenic patients. It is proposed that RHA rats might be an useful animal model for the study of vulnerability to some schizophrenic symptoms. This conclusion is supported by data that indicate that latent inhibition deficits are a characteristic attentional abnormality of these diseases.

Photokilling mechanisms induced by zinc(II)-phthalocyanine on cultured tumor cells.

The photosensitizing effects of liposomal zinc(II)-phthalocyanine (ZnPc) on HeLa cells, with emphasis on morphological changes and mechanisms for cell death, have been studied. No dark toxicity for ZnPc alone was found. Incubation for 1 h with ZnPc followed by red light irradiation induced a variable decrease in the surviving of cells, which was related to both drug concentration and irradiation time. A lethal photodynamic effect (100% of the cells are killed: LD100) was induced by 5 x 10-6 M ZnPc and 5-min irradiation, whereas a sublethal effect (60% of the cells are killed: LD60) was detected with 10 7 M ZnPc and 3 min of red light. Toluidine blue and Hoechst 33258 staining showed characteristic alterations of cell morphology. Numerous bubbles on the plasma membrane were found immediately after an LD100 treatment, and a necrotic morphology appeared 24 h later. On the contrary, severe cell shrinkage with nuclear fragmentation. characteristic of apoptosis. was observed 8 and 24 h after LD60 treatments. In this case, propidium iodide-acridine orange labeling and the TUNEL assay confirmed the occurrence of apoptosis. The highest amount of apoptotic cells appeared 24 h after LD60 treatments, particularly in detached cells, as revealed by cell counting and DNA electrophoresis. Both apoptotic and necrotic mechanisms for cell death occur in HeLa cells in dependence on the experimental protocol of ZnPc photodynamic treatments.