Behavioral effects of L-tryptophan and p-chlorophenylalanine after adrenalectomy or dexamethasone administration in rats

Effects of acute administration of L-tryptophan (L-TRP. 250.0 mg/kg, i.p.) on active avoidance conditioning and "open-field" behavior were studied in male rats after adrenalectomy of dexamethasone administration. L-TRP inhibited the acquisition and reproduction of active avoidance reaction in adrenalectomized and dexamethasone-treated rats. Moreover, L-TRP decreased horizontal locomotor activity and grooming behavior in the "open field" on adrenalectomized rats. On the contrary, p-CPA restored the active avoidance conditioning in adrenalectomized rats and rats with excess of glucocorticoids. Also, p-CPA increased the total locomotor activity and grooming behavior in the "open field" in adrenalectomized rats, but decreased horizontal locomotor activity and enhanced emotional reaction in dexamethasone-treated rats in the "open field".     

The effect of sex steroid hormones on interhemispheric asymmetry in rats]

The effect of gonadectomy and sex-steroid hormones treatment on functional interhemispheric asymmetry to the reaction of pain cry avoidance of another species (emotional reactions) and motor and exploratory activity of open-field behavior in Wistar rats of 3 months old has been investigated. A spreading depression technique for hemisphere inactivation has been used. The hemispheric asymmetry of the reactions in intact rats was characterized by sex dimorphism; the left hemisphere dominated to a great extent in males than in females under the control of emotional reactions; in motor and exploratory activity in open-field behavior of rats the left hemisphere dominated in males and the right one--in female. In both sexes the neonatal gonadectomy levelled the interhemispheric differences in reactions under investigation. The following treatment of females with estradiol and males with testosterone didn't restore the asymmetry. After the castration at the age of 3 months the correlation between the size and direction of interhemispheric differences became reverse. The treatment of females with testosterone and males with estradiol both castrated in adulthood restored the interhemispheric asymmetry in males and had no effect in females. The treatment of intact rats with hormones of opposite sex led to the enhancement of left hemisphere dominance in motor and exploratory activity in males and levelled the asymmetry in females. It has been shown that in adult rats sex-steroids effect predominantly the right hemisphere.     

The effect of a deficiency of the hormones of the peripheral endocrine glands on behavioral, learning and memory processes]

A comparative study of the effects of thyroid, adrenal, and gonadal deficit on capability for learning, retention of memory traces, and behavior was carried out in male rats under conditions of hormonal disbalance produced by extirpation of the endocrine glands. Behavior of animals was tested during the active and passive avoidance learning and in the open field. It was found out that the extirpation of the peripheral endocrine glands impairs learning and reproduction of the acquired reaction and alters the behavior. The results suggest that corticosteroid hormones take part in learning and behavior. Gonadal and thyroid hormones appear to exert a modulating influence on the higher nervous activity.     

Comparative study of the psychotropic activity of tuftsin and its analogs

Tuftsin and its Leu1 and D-Arg4 analogs displayed stimulating activity in experimental behavioral despair in mice. In rats with different types of emotional reactions and with destroyed catecholamine terminals (6-OHDA treatment), tuftsin increased exploratory activity, with fear manifestations being decreased and avoidance behavior improved. This was shown while testing the rats in the "open field" and according to the ability to accomplish an extrapolation task of avoiding critical stress-situation. Leu1-tuftsin increased the emotional stress and sharply hindered the avoidance reaction, while D-Arg4-tuftsin modulated the behavior of the animals with increased emotional reactivity and made the avoidance behavior prompter. Pentapeptide, an inhibitor of tuftsin stimulation of phagocytosis, had no significant effect on the behavior. Modifications in the structure of tuftsin resulted both in the changes in phagocytosis-stimulating activity and the appearance of other psychotropic effects.     

Studying adaptive changes in the behaviour of infected hosts: a long and winding road

The effect of isolation on exploratory behavior has been shown to differ depending on the developmental stages of male rats. However, there has been little systematic comparison of the frequencies and the patterns of exploratory behavior across the developmental stages. The present study assessed the frequencies of exploration using the emergence test and exploratory patterns in the open-field test in three developmental stages of male rats: juvenile, post-puberty, and adult. A lower propensity for exploration was observed in rats isolated during the juvenile stage, as assessed by increased latency and decreased duration of exploratory behaviors compared to pair-reared rats, and this tendency was maintained in adulthood. Altered patterns of exploratory behavior were demonstrated both in rats isolated in adulthood, who showed an increased active pattern, and those pair-reared following puberty, who shifted to a more passive pattern. However, rats isolated during the juvenile stage did not change their exploratory patterns following puberty. These results suggest that the changes in the exploratory pattern, which can be observed in adulthood, are associated with the emergence of adult-like dominance relationships. Juvenile-isolated rats did not show these changes following puberty, suggesting the importance of social interaction as juveniles for the ontogenetic emergence of behavioral flexibility implicated in the regulation of exploratory patterns.     

Interaction between isolation rearing and social development on exploratory behavior in male rats

The effect of isolation on exploratory behavior has been shown to differ depending on the developmental stages of male rats. However, there has been little systematic comparison of the frequencies and the patterns of exploratory behavior across the developmental stages. The present study assessed the frequencies of exploration using the emergence test and exploratory patterns in the open-field test in three developmental stages of male rats: juvenile, post-puberty, and adult. A lower propensity for exploration was observed in rats isolated during the juvenile stage, as assessed by increased latency and decreased duration of exploratory behaviors compared to pair-reared rats, and this tendency was maintained in adulthood. Altered patterns of exploratory behavior were demonstrated both in rats isolated in adulthood, who showed an increased active pattern, and those pair-reared following puberty, who shifted to a more passive pattern. However, rats isolated during the juvenile stage did not change their exploratory patterns following puberty. These results suggest that the changes in the exploratory pattern, which can be observed in adulthood, are associated with the emergence of adult-like dominance relationships. Juvenile-isolated rats did not show these changes following puberty, suggesting the importance of social interaction as juveniles for the ontogenetic emergence of behavioral flexibility implicated in the regulation of exploratory patterns.     

The effect of administering corticoliberin into the striatum on the open-field and shuttle-box behaviors of KHA and KLA strain rats]

The effects of corticotropin-releasing hormone (CRH) injected into the dorsal neostriatum on the open-field and shuttle-box behavior were studied in rats with high (Koltushi high avoidance, KHA) and low (Koltushi low avoidance, KLA) capability for avoidance learning. The effects of this hormone on the behavior of these rat strains were different. In KLA rats with passive strategy of behavior the CRH injection led to a rapid locomotor activation in the open field, while the rats with active behavioral strategy (KHA) reacted to the injection by a significant decrease in locomotion and change for the passive mode of behavior. The same CRH effects on locomotion were obtained in the shuttle-box experiments. Moreover, in the KLA rats the neurohormone injection resulted in an improvement of avoidance learning in contrast to the KHA rats, in which CRH substantially impaired avoidance learning. The obtained evidence is discussed in terms of the important role of striatal CRH in the choice of behavioral strategy in stress.     

Modulation of behavior of mice of different genotypes by serotonin antibodies

The effect of active immunization with conjugated serotonin-protein on the "open-field" behaviour and passive avoidance conditioning was studied in genetically different mice strains (C57BL/6 and BALB/c). The obtained immunophysiological effects of serotonin antibodies depended on genetically determined characteristics of animal behaviour. Serotonin antibodies altered rearing and crossings of the "open-field" center and retention of passive avoidance learning in C57BL/6 mice. The active immunization with conjugated serotonin-protein of BALB/c mice resulted in modulation of the "open-field" latency and both training and testing of passive avoidance behaviour.     

Comparative studies with cyclic and linear somatostatin on active avoidance behaviour and open-field activity in rats

The action of cyclic and linear somatostatin on active avoidance and open-field behaviour was investigated in rats. Both peptides inhibited the extinction of the avoidance behaviour and slightly but not significantly increased the intertrial activity (ITR). Both peptides increased ambulation and rearing activity in a dose related fashion, while the grooming and defecation rates were not changed. Since both peptides are capable of increasing the locomotor performance this action might contribute to the effect exerted on the extinction of active avoidance behaviour.     

Natural autoantibodies against MP65 and ACBP14/18 and ontogenic formation of rat nervous system

It was demonstrated that passive immunization of pregnant female rats against MP65 and ACBP14/18 proteins leads to stable changes in offspring behavior (deviations in acquisition of active avoidance in a shuttle-box and changes in the open-field behavior). Immunomorphological data about localization of MP65 and ACBP14/18 proteins in brain slices of adult rats and rat embryos are presented. The obtained results are discussed in terms of the influence of maternal humoral immunity on the formation of fetal nervous system during intrauterine development.     

Functional inactivation of the hippocampus by controlled neuroimmunization

The method of immunization with hippocampal tissue cytosol was employed for functional disturbance of hippocampus in newborn and mature rats. This influence resulted in behavioral disorders resembling the hippocampectomy consequences. There were ++non-decremental motor activity and rearing in "open field" test and an improvement in acquisition of active avoidance response in adult rats (250-300 g). In young animals the decreased levels of motor and exploratory activity in "open field" and difficulties in active avoidance learning (in 40 days) were the main features of hippocampal disturbance. In case of immunization with neocortical cytosol no significant alterations in behavior were revealed.     

Gender differences in development of exploratory activity in rats

The dynamics of exploratory activity in male and female Wistar rats before weaning and over the course of puberty was investigated. Behavior of animals was examined on the 18th, 35th, and 50th postnatal days in a modified light-dark test and on the 24th postnatal day in an open-field test. It was found that exploratory activity of males considerably changed over the course of puberty period. From the 18th to 35th postnatal days, the number of animals exploring a light compartment increased. From the 35th to 50th postnatal days, the duration of the light compartment investigation increased. The only change in exploratory activity of female rats consisted in an increase in the number of transitions between the light and dark compartments from 35th to 50th postnatal days. The results suggest different mechanisms of exploratory behavior development in male and female rats.     

Passive avoidance performance correlates with catecholamine turnover in discrete limbic brain regions

Experimentally naive male rats were sequentially tested for an exploratory (open-field) and a one-trial learning passive avoidance behavior. Subsequently, α-MPT-induced disappearance of noradrenaline (NA) and dopamine (DA) was determined in microdissected brain regions. The animals were classified as good or poor avoiders on the basis of their performance in passive avoidance retention test. Trained controls were subjected to the same training except of electric foot-shock during the learning trial. The rate constant of NA disappearance was higher in the hippocampal dentate gyrus of the good vs. poor avoiders. In the good avoiders, the rate constant of DA disappearance was significantly higher in the central nucleus of the amygdala. The different turnover of catecholamines in the dorsal hippocampus and the amygdala in relation to passive avoidance performance suggests that individual differences in memory and/or learning may correlate with the catecholamine turnover of certain limbic structures.     

Effects of D2 receptor agonist and antagonist on behavior of intact and ovariectomized rats

The involvement of D2 dopaminergic receptors in behavioral responses during ovary cycle was assessed in adult intact female rats and ovariectomized (OVX) female rats. Quinperole (0.1 mg/kg), D2 receptor agonist and sulpiride (10.0 mg/kg), D2 receptor antagonist were injected chronically to adult intact and ovariectomized (OVX) female rats either separately or in combination with 17beta-estradiol (0.5 microg) within 14 days. Behavior of these animals was assessed in the "open field" test, whereas passive avoidance performance served as a model of learning. In intact rats, the passive avoidance performance was observed only in metestrous and diestrous. Chronic quinperole administration to intact females resulted in the appearance of the passive avoidance performance in proestrous and estrous, as distinct from the control animals. The passive avoidance performance was not reproduced in OVX rats. Quinperole per se or in combination with 17beta-estradiol completely restored the passive avoidance performance in OVX rats. Moreover, quinperole or sulpiride administration to OVX rats increased horizontal locomotor activity, exploratory behavior, and grooming behavior.     

Effects of intracerebroventricular administration of a caspase-3 inhibitor Z-DEVD-FMK on behavior of rats

Rats received intracerebroventricular injections of z-DEVD-FMK (caspase-3 inhibitor) or z-FA-FMK (control peptide) in a dose of 3 nmol. Administration of z-DEVD-FMK significantly decreased the number of avoidance reactions in some blocks of trials in active avoidance (shuttle box) learning. However, only slight effect of the caspase inhibitor across the session was found. Z-DEVD-FMK impaired development of some essential components of the two-way active avoidance performance, such as escape reaction, conditioned fear reaction, and inter-trial crossings. Z-DEVD-FMK did not impair working memory in the spontaneous alternation behavior paradigm. Z-DEVD-FMK affected neither emotionality nor locomotor activity in the open-field test. It also did not influence behavior in the light-dark chamber. Measurement of caspase-3 activity in rat brain regions involved in active avoidance learning revealed z-DEVD-FMK-related inhibition of the enzyme activity most pronounced (about 30%) in the fronto-parietal cortex; a similar effect was close to significant in the hippocampus. The results suggest the involvement of brain caspase-3 in selected forms of learning.     

Correlated variability in motor activity and emotionality in selecting rats for high and low values of active avoidance conditioned reflexes

The open-field behaviour of rats selected for high and low active avoidance level was studied. The data obtained showed the correlated response of two selected lines for avoidance ability with the locomotor activity and emotional reactivity in the open-field situation. The line of a low avoidance value had the low activity level and high defecation score in comparison to the alternative one and to progenitory Krushinsky--Molodkina strain. The correspondence of learning ability and emotionality-motivation performance has been discussed.     

Spontaneous and conditioned behavior of Wistar and Long Evans rats

Spontaneous behavior (locomotion, feeding, drinking, and exploration in a two box apparatus) as well as conditioned behavior (passive and active avoidance responding, and freezing in the light-dark box apparatus) were studied in naive male Wistar and Long Evans rats. Concerning spontaneous behavior, Long Evans rats were more active during both light and dark periods, and showed better exploratory performance than Wistar rats. Concerning conditioned behavior, Long Evans rats acquired and retained better active and passive avoidance responses, and exhibited longer initial freezing than Wistar rats in the range of 0.6-1.4 mA footshocks. The results better define the important behavioral differences existing between the two strains, Long Evans rats showing consistently a higher level of alertness and a better conditioned performance.     

Typological features of behavior and memory in Norway rats selected for absence of aggression toward a man

Features of behavior and retrieval of passive conditioned avoidance on a new and forgotten stimuli were compared in Wistar rats and Norway rats bred for the absence of aggression toward a man. As distinct from white rats, grey rats were characterized by low anxiety and high locomotor exploratory activity in the elevated plus maze and dark-light chamber. Norway rats demonstrated better avoidance performance with active defensive behavioral strategy than Wistar rats. Latent inhibition during conditioning with a previously forgotten situational stimulus was the same in both rat strains. The results are discussed in terms of the use of grey rats as a model for an in-depth analysis of the mechanisms of memory optimization.     

Prefrontal cortex aspiration in pups and juvenile rats: behavioural changes and recovery of function

Male Wistar rats sustaining prefrontal cortex aspiration or sham operation at 6 days or 30 days of age were submitted to the following behavioural tests: open-field, acquisition and retention of two-way active as well as passive avoidance tasks. In the open-field the locomotor activity proved enhanced in all the aspirated animals and this enhancement lasted for 30 days. In the two-day active avoidance task, an acquisition deficit was observed in both aspirated groups; but when retrained one month later, they were able to acquire the avoidance task like sham-operated rats and no difference appeared between the groups aspirated at 6 or at 30 days of age. Concerning the passive avoidance task, no difference could be detected between aspirated and sham-operated animals of both groups except that the rats aspirated at an early age (6 days) seemed to display a better avoidance ability in the retention test. These behavioural alterations (hyperactivity and impairment of the acquisition of the 2-way active avoidance) resulted from the prefrontal cortex aspiration, at whatever age this aspiration was performed (6 days or 30 days). They disappeared after a postoperative recovery period of about one month, as evidenced by this longitudinal study.     

Omega-3 fatty acids deprivation affects ontogeny of glutamatergic synapses in rats: Relevance for behavior alterations

Essential omega-3 polyunsaturated fatty acids (ω3) are crucial to brain development and function, being relevant for behavioral performance. In the present study we examined the influence of dietary ω3 in the development of the glutamatergic system and on behavior parameters in rats. Female rats received isocaloric diets, either with ω3 (ω3 group) or a ω3 deficient diet (D group). In ontogeny experiments of their litters, hippocampal immunocontent of ionotropic NMDA and AMPA glutamatergic receptors subunits (NR2 A\B and GluR1, respectively) and the alpha isoform of the calcium-calmodulin protein kinase type II (αCaMKII) were evaluated. Additionally, hippocampal [³H]glutamate binding and uptake were assessed. Behavioral performance was evaluated when the litters were adult (60 days old), through the open-field, plus-maze, inhibitory avoidance and flinch-jump tasks. The D group showed decreased immunocontent of all proteins analyzed at 02 days of life (P2) in comparison with the ω3 group, although the difference disappeared at 21 days of life (except for αCaMKII, which content normalized at 60 days old). The same pattern was found for [³H]glutamate binding, whereas [³H]glutamate uptake was not affected. The D group also showed memory deficits in the inhibitory avoidance, increased in the exploratory pattern in open-field, and anxiety-like behavior in plus-maze. Taken together, our results suggest that dietary ω3 content is relevant for glutamatergic system development and for behavioral performance in adulthood. The putative correlation among the neurochemical and behavioral alterations caused by dietary ω3 deficiency is discussed.