György Bárdos

Chronic mild stress generates clear depressive but ambiguous anxiety-like behaviour in rats

A 3-week chronic mild stress (CMS) protocol decreased sucrose preference of rats and increased immobility in the forced swim test. It also induced social avoidance and increased grooming, but acted as if reducing anxiety in the plus-maze. Sucrose preference and social avoidance, but not other measures of the behaviour, showed significant correlation. We conclude that CMS-induced depression-like behaviour is associated with social avoidance, a seemingly anxiety-related measure, but not with other anxiety-like traits in rats.

Index Finger Movement Imitation by Human Neonates: Motivation, Learning, and Left-Hand Preference

Imitation of a fine motor movement, index finger protrusion, was examined in 39 neonates using an ethologically based objective coding system. Results confirmed that imitation of finger movements exists, and infants demonstrated “learning” as imitation developed through an incomplete imitation stage. Neonatal imitation was more frequently left-handed, an early sign of laterality in motivation to be investigated further. The existence of index finger imitation in human neonates indicates that volitional control of individuated finger movements develops much earlier than previously thought. The differential increase of index finger protrusion movements during the imitation periods suggests that this behavior is not an automatic response triggered by general arousal but instead is a true indicator of purposeful neonatal imitation.

BGP-15, a hydroximic acid derivative, protects against cisplatin- or taxol-induced peripheral neuropathy in rats

The neuroprotective effect of BGP-15 against peripheral sensory neuropathy was studied in rats that were exposed to short-term cisplatin or taxol administration. The changes of nerve conduction velocity were determined in situ after treating the Wistar rats with BGP-15 (50, 100, and 200 mg/kg po daily doses throughout the experiment), cisplatin (1.5 mg/kg ip daily dose for 5 days), or taxol (5.0 mg/kg ip daily dose every other day in a 10-day interval) alone or giving the test compound in combination with cisplatin or taxol. Electrophysiological recordings were carried out in vivo by stimulating the sciatic nerve at both sciatic notch and ankle site. Neither motor nor sensory nerve conduction velocity was altered by any dose level of BGP-15 tested. Both anticancer drugs decreased the sensory nerve conduction velocity (SNCV). BGP-15 treatment prevented the impairment of SNCV either in part or totally in the cisplatin- or taxol-treated groups. This neuroprotective potential of BGP-15 could be well correlated with its recently described poly(ADP-ribose) polymerase- inhibitory effect and its ability to protect against the damages induced by the increased level of reactive oxygen species in response to anticancer treatment.

Stress-related endocrinological and psychopathological effects of short- and long-term 50 Hz electromagnetic field exposure in rats

It is believed that different electromagnetic fields do have beneficial and harmful biological effects. The aim of the present work was to study the long-term consequences of 50 Hz electromagnetic field (ELF-EMF) exposure with special focus on the development of chronic stress and stress-induced psychopathology. Adult male Sprague-Dawley rats were exposed to ELF-EMF (50 Hz, 0.5 mT) for 5 days, 8h daily (short) or for 4-6 weeks, 24h daily (long). Anxiety was studied in elevated plus maze test, whereas depression-like behavior of the long-treated group was examined in the forced swim test. Some days after behavioral examination, the animals were decapitated among resting conditions and organ weights, blood hormone levels as well as proopiomelanocortin mRNA level from the anterior lobe of the pituitary gland were measured. Both treatments were ineffective on somatic parameters, namely none of the changes characteristic to chronic stress (body weight reduction, thymus involution and adrenal gland hypertrophy) were present. An enhanced blood glucose level was found after prolonged ELF-EMF exposure (p=0.013). The hormonal stress reaction was similar in control and short-term exposed rats, but significant proopiomelanocortin elevation (p<0.000) and depressive-like behavior (enhanced floating time; p=0.006) were found following long-term ELF-EMF exposure. Taken together, long and continuous exposure to relatively high intensity electromagnetic field may count as a mild stress situation and could be a factor in the development of depressive state or metabolic disturbances. Although we should stress that the average intensity of the human exposure is normally much smaller than in the present experiment.

Gender-Related Heart Rate Differences in Human Neonates

The aim of the present study was to examine gender-related differences in heart rate of human neonates controlled for their behavior. Previous studies could not find any difference in male and female fetuses and newborns, although this gender-dependent difference clearly exists in children and adults. The heart rate of 99 newborns (47 girls and 52 boys) was measured with simultaneous video recording of their behavior. Results proved that alert newborns showed the same difference as adults: boys had a significantly lower baseline heart rate than girls. This suggests that heart rate is gender-dependent from birth onward.

Placebo Effects in Sport and Exercise: A Meta-Analysis

The empirical foundation of the ‘placebo effect’ is presented briefly, which is followed by the meta-analysis of the relatively few published reports that have investigated placebo effects in sports performance. Based on the analysis of the fourteen studies included in the meta-analysis, an overall medium effect size (0.4, 95% CI ranged from 0.24 to 0.56) was found. Homogeneity of effect sizes (χ2 (13, N = 196) = 9.35, p = 0.75) and the feasibility of possible explanation models were also tested. In various sports (e.g. cycling, running, weightlifting) the investigation of the placebo effect on various physiological or performance measures (e.g. muscle power, heart rate, running speed) and psychological attributes (e.g. perceived exertion, post-experiment interviews) yielded significant results. Indeed, the common finding of the reviewed studies was that from the point of view of the athletes there is substantial performance enhancement as a result of different forms of placebos. However, the interpretation of some of the results may be limited by methodological shortcomings. Based on the reviewed articles and further questions emerging from them, methodological recommendations as well as possible research ideas are suggested for further inquiries in the area.

Changes in synaptic efficacy in rat brain slices following extremely low-frequency magnetic field exposure at embryonic and early postnatal age.

An earlier study demonstrated changes in synaptic efficacy and seizure susceptibility in adult rat brain slices following extremely low‐frequency magnetic field (ELF‐MF) exposure. The developing embryonic and early postnatal brain may be even more sensitive to MF exposure. The aim of the present study was to determine the effects of a long‐term ELF‐MF (0.5 and 3 mT, 50 Hz) exposure on synaptic functions in the developing brain. Rats were treated with chronic exposure to MF during two critical periods of brain development, i.e. in utero during the second gestation week or as newborns for 7 days starting 3 days after birth, respectively. Excitability and plasticity of neocortical and hippocampal areas were tested on brain slices by analyzing extracellular evoked field potentials. We demonstrated that the basic excitability of hippocampal slices (measured as amplitude of population spikes) was increased by both types of treatment (fetal 0.5 mT, newborn 3 mT). Neocortical slices seemed to be responsive mostly to the newborn treatment, the amplitude of excitatory postsynaptic potentials was increased. Fetal ELF‐MF exposure significantly inhibited the paired‐pulse depression (PPD) and there was a significant decrease in the efficacy of LTP (long‐term potentiation induction) in neocortex, but not in hippocampus. On the other hand, neonatal treatment had no significant effect on plasticity phenomena. Results demonstrated that ELF‐MF has significant effects on basic neuronal functions and synaptic plasticity in brain slice preparations originating from rats exposed either in fetal or in newborn period.

The effect of chronic alcohol treatment on the radial maze performance of rats

The effect of chronic alcohol drinking on maze behaviour was studied in laboratory rats. Thirteen animals received 20% alcohol for 15 weeks ad libitum, and 18 were kept under identical conditions drinking tap water. Both groups were then tested twice within one day for performance in an 8 arm radial maze after 48 h fluid deprivation. Reinforcing fluid droplets were placed at the end of each arm only at the beginning of the test. Total and erroneous entries to the arms, total time spent until reaching the criterion, and strategy of arm choice was recorded for each animal. Activity of the groups did not differ significantly, nor were differences in choosing strategy found. Alcoholic rats, however, showed a significant loss of performance in the second test: they frequently entered arms already visited, and in a number of cases were unable to complete the test within time. These and earlier findings suggest no impairment of learning ability or short term memory, but rather some kind of rigidity and invariability of behaviour.

Changes in synaptic efficacy and seizure susceptibility in rat brain slices following extremely low-frequency electromagnetic field exposure

The effects of electromagnetic fields (EMFs) on living organisms are recently a focus of scientific interest, as they may influence everyday life in several ways. Although the neural effects of EMFs have been subject to a considerable number of investigations, the results are difficult to compare since dissimilar exposure protocols have been applied on different preparations or animals. In the present series of experiments, whole rats or excised rat brain slices were exposed to a reference level-intensity (250-500 microT, 50 Hz) EMF in order to examine the effects on the synaptic efficacy in the central nervous system. Electrophysiological investigation was carried out ex vivo, on neocortical and hippocampal slices; basic synaptic functions, short- and long-term plasticity and seizure susceptibility were tested. The most pronounced effect was a decrease in basic synaptic activity in slices treated directly ex vivo observed as a diminution in amplitude of evoked potentials. On the other hand, following whole-body exposure an enhanced short- and long-term synaptic facilitation in hippocampal slices and increased seizure susceptibility in neocortical slices was also observed. However, these effects seem to be transient. We can conclude that ELF-EMF exposure exerts significant effects on synaptic activity, but the overall changes may strongly depend on the synaptic structure and neuronal network of the affected region together with the specific spatial parameters and constancy of EMF.

Modern health worries, subjective somatic symptoms, somatosensory amplification, and health anxiety in adolescents

The cross-sectional study aimed at the psychometric evaluation of the Modern Health Worries Scale in adolescents and the exploration of the relationship among modern health worries, somatosensory amplification, health anxiety, and somatic symptoms. A total of 480 secondary school students (aged between 14 and 19 years) completed a set of questionnaires. Four-factor structure of the scale was confirmed by confirmatory factor analysis. Modern health worries were connected to somatosensory amplification and health anxiety, and somatosensory amplification and health anxiety were partial mediators of the connection between modern health worries and somatic symptoms. Perceived vulnerability (conceptualized as somatosensory amplification and health anxiety) appears to build a “social-cognitive-emotional bridge” between symptoms and modern health worries.