Neonatal Handling, Sweet Food Ingestion and Ectonucleotidase Activities in Nucleus Accumbens at Different Ages

Neonatal handled rats ingest more sweet food than non-handled ones, but it was documented only after puberty. Here, we studied the purinergic system in the nucleus accumbens, a possible target for the alteration in the preference for palatable food. We measured the ATP, ADP and AMP hydrolysis mediated by ectonucleotidases in synaptosomes of the nucleus accumbens in periadolescent and adult rats from different neonatal environments: non-handled and handled (10 min/day, first 10 days of life). Before adolescence, we found a decreased ingestion of sweet food in the neonatally handled group, with no effect on ATP, ADP or AMP hydrolysis. In adults, we found a greater ingestion of sweet food in the neonatally handled group, with no effect on ATPase or ADPase activities, but a decreased AMP hydrolysis. The nucleus accumbens is a site of intensive interaction between the adenosinergic and dopaminergic systems. Therefore, adenosine may modulate accumbens’ dopamine neurotransmission differently in neonatally handled rats.     

Inhibition of distress vocalizations in the open field as a function of heightened fear or arousal in domestic fowl (gallus gallus)

Whereas a number of measures of fear (duration of the immobility reaction, duration of freezing in the open field and locomotor activity in the open field) showed differences in the predicted direction between pre-experimentally handled and non-handled chicks, significantly fewer distress vocalizations were observed for the relatively more fearful (non-handled) chicks. This finding does not support the general assumption that a monotonic relationship exists between heightened levels of fear and an increased frequency of the distress call. Results are considered in the context of Bronson's (1968) hypothesis that heightened emotionality may inhibit rather than facilitate the expression of a variety of behavioural patterns associated with the avoidance of fear-arousing stimulation.     

Differences in behavior of impulsive and self-controlled rats in the open-field and light-dark tests

The aim of the study was to reveal the relationship between impulsive behavior in rats, on the one hand, and locomotor activity and emotionality on the other hand. Rats were divided into groups according to their preference for reinforcements of different values. Animals that preferred valuable but delayed reinforcement in more than 60% of cases formed a self-controlled group, whereas rats that selected poor but immediate reinforcements in more than 60% of the cases were considered as impulsive. The two groups of animals were subjected to the "open field" and "light-dark" tests. The impulsive animals more quickly adapted to new surroundings and displayed more pronounced research activity as compared to the self-controlled animals. The level of anxiety was higher in the self-controlled group.     

Neonatal Handling Impairs Spatial Memory and Leads to Altered Nitric Oxide Production and DNA Breaks in A Sex Specific Manner

Early life events lead to behavioral and neurochemical changes in adulthood. The aim of this study is to verify the effects of neonatal handling on spatial memory, nitric oxide (NO) production, antioxidant enzymatic activities and DNA breaks in the hippocampus of male and female adult rats. Litters of rats were non-handled or handled (10 min/day, days 1–10 after birth). In adulthood they were subjected to a Morris water maze or used for biochemical evaluations. Female handled rats showed impairment in spatial learning. They also showed decreased NO production, while no effects were observed in these parameters in male rats. No effects were observed on the number of hippocampal NADPH diaphorase positive cells. In the Comet Assay, male handled rats showed increased DNA breaks index when compared to non-handled ones. We conclude that neonatal handling impairs learning performance in a sex-specific manner, what may be related to NO decreased levels.     

Behavioral effects of bovine lactoferrin administration during postnatal development of rats

We tested the hypothesis that rats consuming bovine lactoferrin (bLf) during postnatal development would show better performance of stressful tasks during adolescence. In the first study, we orally administered bLf (750 mg/kg) once daily between postnatal days 16–34. Rats then underwent a battery of behavioral tests: open field (forced exploration of risky environment), light–dark emergence (voluntary exploration of risky environment), baited holeboard (working and reference memory), food neophobia (preference for familiar versus novel food), forced swim (test for antidepressant efficacy), and shuttle-box escape (learning to escape footshock). bLf-supplemented rats showed less exploration of the risky environment, greater preference for the familiar food odor, and faster escape responses. The effect of bLf on forced-swim behavior depended on sex: immobility increased for males and decreased for females. In the next study, we replaced the forced-swim test with an escape-swim test in which rats learned to use a visual cue to locate an escape platform, and we tested the dose response of bLf on this and the shuttle-box escape test, with subjects receiving vehicle or bLf at 500, 1,000, or 2,000 mg/kg. Under this modified testing battery, improvement of escape from footshock was not observed at any dose. However, males, but not females, showed a significant dose-dependent effect of bLf on acquisition of the water-escape task. On average, males receiving a higher dose mastered the task 20–25 % sooner than rats receiving a lower dose or vehicle. These results offer preliminary evidence that bLf supplementation during development can improve subsequent cognitive performance during stress.     

Liver enzyme adaptation after lithium administration in handled and nonhandled rats.

We have examined the interaction of lithium administration and the infant stimulation procedure of handling on hormonally regulated enzymes of liver. Animals handled in infancy show an increased morning corticosterone level in response to lithium feeding and markedly elevated serum glucose during refeeding following a two day fast, when compared to non-handled control animals. Lithium alters serum corticosterone both in response to the stress of fasting, and during the diurnal cycle following glucose refeeding. The handled and non-handled animals respond differently. These results are consistent with previously reported alterations in feedback regulation of ACTH secretion in handled animals. They also indicate a further modification of this system in response to lithium administration.     

The Influence of Early Life Interventions on Olfactory Memory Related to Palatable Food, and on Oxidative Stress Parameters and Na+/K+-ATPase Activity in the Hippocampus and Olfactory Bulb of Female Adult Rats

The effects of neonatal handling and the absence of ovarian hormones on the olfactory memory related to a palatable food in adulthood were investigated. Oxidative stress parameters and Na+/K+-ATPase activity in the hippocampus and olfactory bulb of adult pre-puberty ovariectomized female rats handled or not in the neonatal period were also evaluated. Litters were non-handled or handled (10 min/day, days 1-10 after birth). Females from each litter were divided into: OVX (subjected to ovariectomy), sham, and intact. When adults, olfactory memory related to a palatable food (chocolate) was evaluate using the hole-board olfactory task. Additionally, oxidative stress parameters and Na+/K+-ATPase activity were measured in the hippocampus and olfactory bulb. No difference between groups was observed considering olfactory memory evaluation. Neonatal handled rats presented an increase in Na+/K+-ATPase activity in the hippocampus and in the olfactory bulb, compared to non-handled ones. Considering the surgical procedure, there was a decrease in Na+/K+-ATPase and catalase activities in sham and OVX groups, compared to intact animals in the olfactory bulb. We concluded that olfactory memory related to a palatable food in adulthood was not affected by neonatal handling or by pre-puberty surgery, with or without removal of ovaries. The difference observed between groups in catalase and Na+/K+-ATPase activity does not seem to be related to the olfactory memory. Additionally, the increase in Na+/K+-ATPase activity (an enzyme that maintains the neurochemical gradient necessary for neuronal excitability) induced by neonatal handling may be related to neuroplastic changes in the hippocampus and olfactory bulb.     

Diurnal behavioral and endocrine effects of chronic shaker stress in mice

Experiments were performed in C57BL/6J male mice to determine 1) light/dark effects of acute and chronic shaker stress on open field behavioral patterns and 2) light/dark effects of chronic stress on plasma corticosterone and oxytocin. Shaker stress was applied acutely (15 min) or chronically (3 or 7 days). Mice were tested in the open field in the light or dark phase of the circadian cycle. For the endocrine study, mice were exposed to 3 days of intermittent shaker stress and sacrificed after the last stress event (09:00 or 19:00 h). Acute or chronic shaker stress had no significant effects on intensity of motor activity and rearing of mice tested under either light condition. Mice tested in the dark phase had higher motor activity and exhibited lower anxiety-like behavior as expressed by central zone activities and had higher emotionality as expressed by increased defecation. Chronic stress increased corticosterone with a greater absolute increase in the dark period. However, the percentage stress-induced increase was not different between the day and night periods. The oxytocin response to stress was observed only during the light phase with no change seen at dark phase. These results show that there is a marked difference in the light/dark pituitary stress response with no alteration in stress induced behavioral changes. They also suggest that there are circadian interactions in the endocrine stress axis that are without consequences for open field behavior.     

Effects of early gentling and early environment on emotional development of puppies

In recent years much interest has been focused on early experiences and numerous studies have been carried out in order to understand their effects on the behaviour of adult animals. The aim of this preliminary study was to assess the effects of early gentling and early environment on the emotional stability of puppies. Forty-three dogs (16 females and 27 males) from seven litters were used. Four of these litters (in total 23 puppies) were raised in a professional breeding kennel, while the remaining litters lived in their owner's home, in a family atmosphere. Half of every litter was gently handled daily from the 3rd day postpartum until the 21st. In order to assess the puppies’ emotionality, an isolation test followed by an arena test were conducted on every puppy at the age of 8 weeks. Video recording of the tests allowed the measurement of each puppy's vocalization and exploratory activity. Data were analysed with the Newmann–Keuls’ test comparing four groups: non-handled puppies raised in family (NHF); handled puppies raised in family (HF); non-handled puppies raised in a professional breeding kennel (NHB); handled puppies raised in a professional breeding kennel (HB).

The results suggest that early environment strongly influences the emotional stability of puppies when put in isolation: latency to the first yelp was longer (p < 0.05) in the HB group (89.46 ± 66.42) compared to NHB (45.90 ± 52.76), NHF (13.10 ± 12.17) and HF (17.90 ± 14.32), and in the NHB compared to NHF and HF; duration of vocalizations was shorter (p < 0.05) in the HB (36.77 ± 54.16) and NHB group (72.80 ± 60.57) compared to NHF (149.78 ± 19.52) and HF (132.50 ± 45.24). Moreover, early gentling had a cumulative positive effect on the emotional development of puppies. For both environments, handled puppies were calmer. In fact, they showed longer latency to vocalize and handled puppies (HB = 119.00 ± 39.85; HF = 97.12 ± 33.56) spent significantly more time (seconds) in exploratory activity (p < 0.05) compared to the corresponding non-handled puppies (NHB = 64.90 ± 34.06; NHF = 57.00 ± 26.61).

Therefore, it is concluded that the deliberate inclusion of gentling during early puppyhood would be advantageous to the emotional development and welfare of the puppy, in particular for those at risk of limited or poor tactile stimulation in the early weeks.     

Orienting behavior of female white rats in estrus cycle and its dependence on handling

Characteristics of orienting behavior of intact and handled female white rats were studied in the "open field" test. Experimental group of animals were formed according to stages of estrous cycle: (1) diestrus, (2) proestrus, (3) estrus, and (4) metestrus. The stage of the cycle was determined by vaginal smears. Over the period of 10 days rats were handled daily for 5 minutes. No behavioral changes over the course of estrous cycle were found in intact rats. Handling revealed some behavioral features related to the levels of steroid hormones in reproductive cycle. Most prominent changes in orienting behavior were observed at transition from estrous to metestrous. At the stage of estrous motor activity was maximal and grooming was minimal. The maximal contrast in the structure of orienting behavior was observed between estrous and diestrous stages.     

模拟失重对大鼠情绪影响的初步研究

目的:研究模拟失重状态对大鼠情绪产生的影响。方法:从20只雄性SD大鼠中挑选16只分成正常组和模拟失重组(n=8),采用摄食和体重测定、旷场试验、糖水偏好度测试及情绪唤醒程度评定四种方法,对大鼠进行情绪检测。结果:①模拟失重组大鼠摄食量下降,体重增加速率较正常组显著减小;②模拟失重14 d后,大鼠的运动力下降,爬格数显著低于正常组(P<0.05),自我修饰次数比正常组明显增多,洗脸与理毛次数均显著高于正常组(P<0.01);③与正常组比较,模拟失重大鼠具有更高水平的情绪唤醒度;④模拟失重14 d对大鼠的糖水偏好度无显著影响。结论:模拟失重14 d使大鼠出现抑郁、紧张和焦躁等负面情绪,出现一定程度的神经质反应,但不会出现快感缺乏。     

Characteristics of biochemical processes of the liver in rats with various types of open-field behavior

Respiration and phosphorylation of liver mitochondria, lipid spectrum of the blood serum activity of hepatocytes main microsomal enzymes were studied in outbred rats with various emotionality. It was found that in low-emotional rats, the intensity of phosphorylation processes in liver mitochondria and enzymes activity of hematocytes microsomal oxidative system responsible for detoxication processes,-- was significantly higher than in low-emotional animals. Analogous differences were found in the lipid blood spectrum and in liver mitochondria antioxidant activity of animals with different emotionality. It is supposed that there is an inter-connection between animals behaviour in the open field and the character of biochemical processes in the liver.     

Emotional reactivity of rats and their progeny after hormonal modification of intrauterine development

Emotional reactivity of two rat generations was estimated in open field test and by the corticosteroids level under motor restriction after hydrocortisone injections (50 mg/kg) to their mothers (the 1st generation) or grandmothers (the 2nd generation) on 16 and 18 days of gestation. The 3-, 6- or 12-month-old males and females of the 1st generation had decreased emotional reactivity. On the contrary, the animals of the 2nd generation had increased defecation, but decreased ambulation scores in the open field test, that characterised them as more emotional in comparison to the control rats. Thus, the corticosteroids can be a factor of "nongenetic transmission of information" in the development of animals' emotional reactivity mechanisms.     

Enriched early experiences of mice underexpressing the beta-amyloid precursor protein restore spatial learning capabilities but not normal openfield behavior of adult animals

We have previously reported severely impaired spatial learning in mutant mice underexpressing a shortened variant of the beta-amyloid precursor protein (beta-APPtheta/theta). This targeted mutation is functionally equivalent to a null mutation. It also disturbs behavioral and neurological maturation with deficits emerging mainly between postnatal day (pd) 11 and 19. Such early tested mice exhibited almost no genotype-related difference in Morris water maze learning, raising the possibility that early handling might have compensated for genetic deficits. To verify this effect, we compared watermaze learning and open field behavior of 66 adult mutant and wildtype mice having been handled during pd 3-27 with that of 70 non-handled mutant and wildtype mice. Neurological testing during pd 3-27 markedly reduced time near wall and improved spatial retention of adult mutants, restoring their learning capabilities to wildtype levels. Early handling did not cure the mutation associated activity deficit in the open field, but mainly increased center field exploration in both mutants and wildtypes. In a follow-up experiment we analyzed whether an early (pd 3-10, n = 22) or middle (pd 11-19, n = 24) period of handling in form of neurological testing had differential effects on adult behavior. Mice handled during pd 11-19 had slightly shorter escape times than mice handled during pd 3-10 but were not significantly different in other behavioral measures. There were no sex related differences. Correlational and factor analysis showed that both the mutation and early handling had pleiotropic behavioral effects, resulting in differentially impaired mutants depending on the test situation. Likewise, early handling affected not only thigmotactic tendencies but also, more subtly, other behavioral components underlying water maze learning. We conclude that early postnatal stimulation can prevent mutation induced learning deficits in adult mice, but probably through other developmental mechanisms than those affected by the mutation. This implies that some behavioral impairments related to beta-APP malfunction may be corrected through simple treatments.     

Spontaneous light or dark preference in albino mice?

The present experiment examined spontaneous visual choice behaviour and acquisition of a positively reinforced visual discrimination task in Swiss albino mice. In experiment I animals were given 4 consecutive trials in which they could freely enter either a dimly illuminated or a darkened arm of a Y-maze; the position of the light stimulus was randomized across trials. D groups and L groups were tested during the dark and the light period of the day respectively. Results revealed a significant spontaneous preference for the illuminated arm of the maze, independent of the testing period. It is suggested that the dim light has a reinforcing value because it provides additional information about a novel environment. In a second experiment an appetitive visual discrimination task was carried out in the same Y-maze. After a pretraining period, half the animals were reinforced in the illuminated arm and half were reinforced in the darkened one, on five consecutive days. On the first test session all groups of animals chose the illuminated arm significantly more frequently, whereas light/dark choices reached chance level on the last test session. Discrimination learning was not acquired and a behavioural analysis revealed an increasing tendency to a side preference across testing.     

Selection of behavioral test parameters for estimation of typological features of rat behavior

Behavior of 86 rats was examined in three behavioral tests, i.e., open field, forced swimming and emotionality by F. King. The results of statistical analysis of all the indices obtained with application of factor analysis suggest that the three tests characterize four relatively independent behavioral components: emotionality, locomotor-exploratory activity, olfactory performance, and resistance to adverse emotional factors. A contribution of each measured parameter to the above components was estimated. Such an approach makes it possible to reasonably select most important behavioral features when estimating locomotor activity and emotionality of animals.     

Interaction between pre-weaning undernutrition and post-weaning environmental enrichment on somatic development and behaviour in male and female rats

Male and female rats were undernourished from birth to 30 days by restricting access to the lactating mother, and then fed ad libitum. At weaning, underfed and normally suckled controls were permanently housed either in pairs in standard cages or in groups of 10 in 1 m³ cages containing ladders, ropes etc. Severe undernutrition during suckling followed by 4 months of refeeding, produced some changes in sexual behaviour in adult males (increased ejaculation frequency) but had no effect on behaviour in open field, dark preference or passive avoidance. Differential post-weaning environment produced significant differences in behaviour, irrespective of previous feeding conditions. Enriched animals were more active and exploratory. Females differed from males in the same direction as enriched from standard, and were more responsive to social and housing conditions.     

The experience in the water maze task can affect the circadian rhythm of locomotor activity

Wistar rats maintained in cages with running wheels and submitted to a skeleton photoperiod or to a light - dark cycle were tested in the Morris water maze. Half of the animals were exposed to the task during their active phase while the other half was exposed during their inactive phase. The effect of the experience in the water maze, a strong arousing event, on the rhythm of wheel-running activity was evaluated. In the first experiment, a group of animals submitted to a skeleton photoperiod was trained every day in the reference memory version of the task. The novel experience in the water maze had a strong phase-dependent masking effect: it produced an intense post-training bout of activity in the animals tested during their inactive phase. Another experiment was run using single working memory sessions in the water maze and with animals submitted to a light - dark cycle. The circadian rhythm of locomotor activity was evaluated on undisturbed days and compared with testing days. The experience in the water maze produced a significant increase in variability of activity onset during both circadian phases. Taken together, the data suggest that there is a modulating effect of the arousing experience in the pool on the overt circadian rhythm of locomotor activity.     

The effect of social isolation of the rat on open field activity and emergence

It has been suggested that naive isolated rats show more “fear responses” than group-housed controls. However, in contrast to previous studies, dark conditions and low noise levels were used to evaluate the latency to emerge from a small chamber into an open field and the subsequent ambulation and rearing behaviour of isolated and group-housed rats. The prediction that these conditions would be conducive to the rapid development of hyperactivity in isolates was confirmed, but there were no significant differences in emergence latency.