Paolo Renzi

Evaluation of the elevated plus-maze and open-field tests for the assessment of anxiety-related behaviour in inbred mice.

The elevated plus-maze test (PM) and open-field test (OF) are routinely used to study anxiety-related behaviour in mouse. However, the data obtained with these tests have often been contradictory, probably because of differences between laboratories in the selection and analysis of behavioural parameters. We have characterised the pattern of mouse anxiety by analysing a number of behavioural parameters with both PM and OF in BALB/c and C57BL/6 mice, two behaviourally distant mouse strains. Twenty-eight variables (15 analysed with PM and 13 with OF) were selected by correlation analysis from those initially recorded with both tests. The scores of the selected variables were first analysed by MANOVAs, and then by principal component analysis (PCA). PCA extracted five factors for PM and four factors for OF. These factors were subjected to a correlation analysis, which showed significant correlation between four of them. The factorial scores of BALB/c and C57BL/6 mice were analysed by MANOVAs, which showed significant effects of both the strain and test used. Our results confirm the multidimensional structure of mouse anxiety-related behaviour as regards both simple components and functional interactions, and comprehensively represent strain- and test-specific features of mouse anxiety-related behaviour.

Amodal Completion in Mouse Vision

The question of whether phenomena of human perception such as amodal completion are also present in visual perception in the mouse was investigated. Three experiments based on a simultaneous-discrimination task were carried out with the aid of a jumping-stand similar to the one used by Lashley. The subjects were 36 male mice (DBA/J); 12 took part in each experiment. After reaching the learning criterion (87% correct responses), the mice performed 15 test trials which were interpolated between the learning trials. The test trials were constructed so as to allow the observation of any perceptual phenomena similar to amodal perception. Of the 36 subjects, 23 reached the criterion necessary to access the test phase. A significant number of them (17 out of 23, χ2 = 5.261, p = 0.021) adopted a decisional strategy that seemed to indicate the occurrence of phenomena similar to amodal completion, and a trend in the same direction was observed in the performance of the other 6 subjects. The results allow the conclusion that a perceptual phenomenon which is similar to amodal completion in humans is present even at this phylogenetic level. Alternative interpretations are discussed.

Potential Therapeutic Effects of Vitamin E and C on Placental Oxidative Stress Induced by Nicotine: An In Vitro Evidence

There have been a few studies that examined the oxidative stress effects of nicotine during pregnancy and lactation. The adverse effect of prenatal smoking exposure on human fetal development and growth has been a major public health issue. Active or passive smoking during pregnancy can result in a wide variety of adverse outcomes, including intrauterine growth retardation (IUGR), prematurity, stillbirth, and the sudden infant death syndrome. Smoking in pregnancy has also been associated with an increased risk of attention deficit and learning problems in childhood. Some studies argued that as a principal component of tobacco smoke, nicotine alone is responsible for the majority of negative reproductive outcomes. Nicotine and its major metabolite cotinine can cross the placental barrier. The level of nicotine in fetal tissues was found to be equal to or greater than the plasma nicotine level in the mothers. The oxidative stress induce by nicotine has been increasingly postulated as a major contributor to endothelial dysfunction. A large body of research has investigated the potential role of antioxidant nutrients in the prevention of endothelial dysfunction in women. Therefore, the present study was undertaken to assess the potential benefit of antioxidant supplementation on markers of placental oxidative stress in an in vitro model of endothelial dysfunction induced by nicotine, since it was previously found that nicotine is able to trigger the placental secretion of stress molecules. In this regard, we evaluated the effects of vitamin C, vitamin E and N-acetylcysteine (NAC), alone or in combination, in placental villi culture after exposure to nicotine. The effect of antioxidant nutrients on trophoblast cells proliferation and vitality was also evaluated. The results obtained suggest that in a patho-physiological condition, such as endothelial dysfunction induced by nicotine, the deleterious effect of reactive oxygen species may be counteracted by an antioxidant therapy, and there is the need to investigate the optimum dosing and timing of antioxidants administration, since an inappropriate antioxidant treatment in pregnant women may have deleterious consequences, reducing placental cells proliferation until to cell death.

The development of postural strategies in children: a factorial design study.

BackgroundThe present study investigates balance control mechanisms, their variations with the absence of visual input, and their development in children from 7 to 11 years old, in order to provide insights on the development of balance control in the pediatric population.MethodsPosturographic data were recorded during 60 s trials administered on a sample population of 148 primary school children while stepping and then quietly standing on a force plate in two different vision conditions: eyes closed and eyes open. The extraction of posturographic parameters on the quiet standing phase of the experiment was preceded by the implementation of an algorithm to identify the settling time after stepping on the force plate. The effect of different conditions on posturographic parameters was tested with a two-way ANOVA (Age × Vision), and the corresponding eyes-closed/eyes-open (Romberg) Ratios underwent a one-way ANOVA.ResultsSeveral posturographic measures were found to be sensitive to testing condition (eyes closed vs. eyes open) and some of them to age and anthropometric parameters. The latter relationship did not explain all the data variability with age. An evident modification of postural strategy was observed between 7 and 11 years old children.ConclusionSimple measures extracted from posturographic signals resulted sensitive to vision and age: data acquired from force plate made it possible to confirm the hypothesis of the development of postural strategies in children as a more mature selection and re-weighting of proprioceptive inputs to postural control in absence of visual input.

Different effects of apomorphine on locomotor activity in C57BL/6 and DBA/2 mice

Abstract The effects of apomorphine on spontaneous locomotor activity have been studied in two inbred strains of mice, the C57BL/6 and the DBA/2. In C57 mice low doses of apomorphine reduced motor activity, while higher doses produced hypermotility. In DBA mice the drug always depressed locomotor activity. The results have also been discussed in relation to the different sensitivities to morphine exhibited by the same two strains of mice.

Naloxone prevents cell-mediated immune alterations in adult mice following repeated mild stress in the neonatal period

Mild stress plus mild pain (solvent injection) applied daily to neonatal mice induces hormonal, behavioural and metabolic changes perduring in the adult life. We investigated whether daily mild stress to neonatal mice induces also long‐term defined changes of immune response, and whether immune changes are prevented through repeated administration of the opioid antagonist naloxone. Mild stress plus solvent injection administered from birth to the 21st postnatal day causes not only behavioural and metabolic changes, but also long‐term (up to 110 days of life) splenocytes modifications, consisting in: increased release of the Th‐1 type cytokines interleukin‐2 (IL‐2) (from an average of 346 to 788 pg ml−1), interferon‐γ (from 1770 to 3942) and tumour necrosis factor‐α (from 760 to 1241); decreased release of the Th‐2 type cytokines IL‐4 (from 49.1 to 28.4) and IL‐10 (from 1508 to 877). Moreover, enhanced natural killer‐cell activity; enhanced proliferative splenocytes properties in resting conditions and following phytohemoagglutinin and concanavalin‐A stimulation are observed. Immunological, behavioural and metabolic changes are prevented by the opioid antagonist (−)naloxone (1 mg kg−1 per day s.c., administered instead of solvent) but not by the biologically inactive enantiomorph (+)naloxone. In conclusion, endogenous opioid systems sensitive to naloxone are involved in long‐lasting enhancement of the Th‐1 type cytokines and cell‐mediated immunological response caused by repeated mild stress administered postnatally.

High-intensity nociceptive stimuli minimize behavioral effects induced by restraining stress during the tail-flick test.

Analgesia following exposure to various stressors is a well-documented phenomenon. Restraint of an animal during the tail-flick test (TFT) represents a potent stressor that can induce both altered baseline latencies and enhanced response to opioids. The present study shows that the use of higher stimulus intensities during TFT minimizes the stress influences produced by restraint on the animals response rendering the test more sensitive to the pharmacological action of analgesic drugs.

Genetic differences in daily rhythms of pain sensivity in mice

A dark phase increase in pain sensitivity was evident in C57BL/6 inbred mice. On the contrary Swiss mice are characterized by decreased nocturnal pain sensitivity. The latter finding is in agreement with a number of previous studies based on albino mice. However, our findings indicate that (1) nocturnal decreased pain sensitivity is not the rule in the mouse and (2) large differences are evident when the onset in peak nocturnal analgesia is considered.

Ultradian rhythms of reaction times in performance in vigilance tasks

This study examined the presence of rhythmic fluctuations in vigilance tasks. The hypothesis was that individual attentional performance is subject to rhythmic variation beyond a linear decrease over time. In the first study the reaction times to an acoustic stimulus were recorded. The analysis of the individual periodograms indicated a rhythm in attentional capacity with periods ranging from 5 to 30 min. These findings indicate that considerable individual variation can be accounted for by considering individual periodicity in performance. Although marked individual differences between subjects are present, the rhythmic fluctuations are stable within each subject and between experimental sessions.

Anxiety-related behaviour in C57BL/6↔BALB/c chimeric mice

In a previous study on anxiety-related behaviours of the genetically and behaviourally distant inbred mouse strains C57BL/6 and BALB/c using the Elevated plus-maze (EPM) and Open-field (OF) apparatuses, we identified a number of variables, the factorial scores of which were grouped by principal component analysis (PCA) into factors specifically describing each inbred strain. We have now studied the effect of C57BL/6 and BALB/c haploid sets of genes on this behaviour by comparing EPM and OF variables of C57BL/6 and BALB/c versus C57BL/6 x BALB/c F1 hybrids (B6CBF1) and chimeric C57BL/6 x BALB/c (CHIM) mice. CHIM mice were made by embryo aggregation and the chimerism degree of their brain was inferred from coat black/white distribution. Discriminant analysis of EPM and OF factorial scores of C57BL/6, BALB/c and CHIM mice showed that CHIM mice with an exceeding (> or =80%) C57BL/6 or BALB/c coat component had behaviours similar to those of the predominant strain, whereas CHIM mice with intermediate chimerism differed from both inbred strains. Additional MANOVA analysis showed that the anxiety behaviour of CHIM mice with intermediate chimerism was similar to that of B6CBF1 mice as for factors not describing the inbred strains, including a motor activity mostly limited to protected areas, with attempts to approach the anxiogenic areas while processing/storing the external information. We conclude that the balanced presence of both C57BL/6 and BALB/c genetic backgrounds, either when carried by the same cell or by different cells, gives rise to a novel stress coping strategy described by factors different from those of the inbred strains.