Age-related characteristics of poststress DNA repair in the myocardium

It has been demonstrated that young and adult rats had age-associated differences in stress-induced lesions and in poststressor repair of DNA synthesis in the myocardium. In both age groups, the DNA repair systems perform an identical scope of work aimed at abolition of poststressor lesions with the difference that in young rats, the repair is completed 2 days and in adult rats 3 days after exposure to stress is discontinued.     

Effect of interleukin-1beta and interleukin-4 on serum albumin parameters in rats with various behavioural characteristics

We studied the effects of pro-inflammatory cytokine interleukin-1beta and antiinflammatory cytokine interleukin-4 on serum albumin parameters in rats with various behavioural characteristics in the open-field test. Under control conditions, the total concentration of serum albumin in active animals was higher than in passive those. However, the ratio of the effective-to-total concentration of albumin (i.e., binding capacity of this protein) was greater in passive rats. Administration of interleukins was accompanied by a decrease in the total content and effective concentration of albumin in passive and, particularly, in active rats. The initial intergroup differences in the ratio of the effective-to-total concentration of albumin were not found after injection of immunomodulating agents. It was mainly related to a more significant increase in this parameter in active animals. An increase in the binding capacity of albumin after cytokine treatment could be associated with conformational changes in the protein molecule. We believe that interleukin-1b and interleukin-4 exert similar effects on the properties of binding sites of serum albumin in rats with various behavioural characteristics.     

Stress responsiveness of the hypophyseal-adrenocortical system in rats with active and passive types of behaviour

No linear differences in the corticosterone basal levels or in its changes following weak stress effects were revealed in rats with active (KHA) or passive (KLA) behavioural strategy. A strong immobilisation stress alone was able to evoke significant linear differences in the hypophyseal-adrenocortical system's responsiveness. The hormonal response to stress was prolonged in the KHA rats as the increased level of corticosterone in the blood of these animals was longer preserved than in the KLA rats. The results suggest both a different sensitivity of the hypophyseal-adrenocortical system and a different velocity of the stress response deactivation in active and in passive animals.     

Changes in the level of oxygen tension in different brain structures of rats in positive and negative emotional states

Changes of oxygen tension (pO2) level in various brain structures were studied in rats in positive and negative emotional states. It is established that pO2 level changes depend on the character of behavioural reactions: "active" type of behaviour (emotionally positive orienting-investigatory, actively defensive) is accompanied by pO2 level increase, and "passive" type of behaviour ("freezing" reaction)--by a decrease of pO2 level. Changes of oxidative brain metabolism observed at "active" and "passive" types of behaviour indicate, respectively, adaptive and nonadaptive character of these behavioural reactions.     

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.     

Disruption of latent inhibition in ISIAH rats with stress-sensitive arterial hypertension

Latent inhibition phenomenon is used in the study of processes of selective attention in the context reinforcing training. The purpose of this study was a comparative analysis of the ability to ignore irrelevant stimuli in hypertensive ISIAH rats and normotensive Wistar rats with different psychoemotional statuses. Latent inhibition was formed in the passive and active avoidance tasks the development of which was preceded by repeated presentation (pre-exposition) conditioned stimulus without reinforcement. In ISIAH rats, disruption of latent inhibition in both behavioural tasks was observed as compared with Wistar rats. These data suggest that the deficit of selection information in ISIAH rats is caused by congenital weakness of internal inhibition in the adaptation to anxiogenic stimuli.     

Effects of training on stress-related behavior of the common marmoset (Callithrix jacchus) in relation to coping with routine husbandry procedures

Using positive reinforcement, J. McKinley trained 12 common marmosets (Callithrix jacchus) to provide urine samples on request. The study then exposed the marmosets to mildly stressful, routine husbandry procedures (i.e., capture and weighing). The nonhuman animals spent less time inactive poststressor as opposed to prestressor. L. Bassett collected matched behavioral data from 12 nontrained marmosets who were less accustomed to human interaction. These animals spent significantly more time self-scratching and locomoting as well as less time inactive, poststressor. Collapsed data from the 2 populations showed increased scent marking, poststressor. These results suggest that locomotion, self-scratching, and scent marking are useful, noninvasive behavioral measures of stress and, thus, reduced welfare in the common marmoset. Overall, nontrained animals showed more self-scratching than did their trained counterparts. It was not possible to collect urine from nontrained marmosets. In response to the stressor, however, trained animals showed no significant change in excreted urinary cortisol. These results suggest that training marmosets may allow them to cope better with routine laboratory procedures.     

Antagonism of caerulein, a CCK-8 receptor agonist, to the behavioral effects of ketamine in mice and rats

It has been established in experiments on male mice and rats that caerulein antagonized the behavioural effects of ketamine, an agonist of phencyclidine receptors. Caerulein (75-375 micrograms/kg) and haloperidol (0.1-1.5 mg/kg) suppressed the stereotyped behaviour and motor excitation induced by ketamine (30 mg/kg) in mice. Caerulein and haloperidol failed to affect ketamine-induced ataxia. Caerulein (10 micrograms/kg) and the opioid antagonist naloxone (5 mg/kg) completely blocked the amnestic action of ketamine (30 mg/kg) in passive avoidance experiments on rats. It seems likely that the suppression of the behavioural effects of ketamine by caerulein is related to its functional antagonism with dopamine and opioid receptors.     

The characteristics of higher nervous activity and of the brain benzodiazepine system in rats subjected to ethanol exposure in the prenatal period

Exposure to ethanol during pregnancy results in the alternation of 3H-diazepam binding to synaptosomal neocortical membranes from the rat offspring. In male experimental rats, 14 days of age, binding level diminished to 11%. In two-month-old control rats Scatchard plot was biphasic. It has been shown that prenatal exposure to ethanol leads to changes in the nature of binding in two-month-age experimental animals, as compared with the control ones. 3H-diazepam binding changes went along with behavioural deviations. In experimental rats locomotor activity was increased in the "open field" test, passive avoidance conditioned reflex retention was decreased and elaboration parameters of active avoidance conditioned reflex were changed, as compared with the control ones. The data obtained show that higher integrative functions were disturbed by prenatal alcoholization. Correlations between benzodiazepine receptor state and behaviour were studied.     

Effect of etimizol on behavioral responses, brain serotonin concentration and plasma corticosteroid levels

The influence of ethymisol on behavioural reactions was studied on 100 albino rats in the "open field" and "passive avoidance" tests. It was shown that a 5 mg/kg dose of this neurotropic drug with synaptic effect, changes behavioural reactions, lowers the general emotional stress and emotional memory of the electro-cutaneous stimulation. Simultaneously the level of corticosteroids in the blood plasma significantly rises, while the serotonin content in the hypothalamus decreases. A direct correlation between the changes in the emotional stress and the content of corticosteroids in blood plasma is noted. The effects of ethymisol partially persists after adrenalectomy. Ethymisol in optimal doses may be used for regulation and lowering of emotional stress.     

The insect neuropeptide proctolin can affect the CNS and the smooth=muscle of mammals

The insect neurotransmitter proctolin can affect different behavioural parameters in rats after intracerebroventricular administration. Proctolin decreased the horizontal exploratory activity and induced a long-lasting analgesia in a hot-plate test. Proctolin lenghthened the passive avoidance latency of rats after post-trial treatment and also in the pre-retention test situation. The self-stimulation rate of rats was significantly diminished after i.c.v. proctolin administration. Proctolin also induced in rat and mouse ileum in vitro a dose-dependent contraction of the gut smooth-muscle that can be blocked by atropine. The results show that an invertebrate neuropeptide (or its fragments) can also be active in mammals. The physiological relevance of the effects observed recently is unknown.     

Piracetam correction of deficient GABA-ergic inhibition due to early postnatal exposure to cycloheximide

Cycloheximide, administered to 7-day-old rats, caused the delay of CNS activity changes in grown-up rats. The animals showed impaired memory function, expressed in the decrease of habituation in the "open field" test, and the alteration of passive avoidance reflex. The increased number of intersignal reactions due to hypermotility was found during elaboration of avoidance reflex. The analysis of evoked potential recovery revealed the deficiency of GABA-ergic inhibition in the neocortex. Piracetam was shown to prevent completely behavioural disturbances and deficiency of GABA-ergic processes in grown-up animals.     

Psycho-emotional manifestations in rats with hippocampal lesions

The study aimed at revealing psycho-emotional manifestations of Wistar rats in a problem situation when they had to solve a food-getting task in a multi-alternative maze. Bilateral lesion of dorsal hippocampus did not affect the learning process while the pattern of psycho-emotional manifestations changed in all the animals irrespective of their individual properties. The pverall effect was manifested in flatness of psycho-emotional responses as a result of reduction of extreme forms of both passive and active stress responses. Individual effects depended on the behavioural phenotype. Hippocampus lesion in initially excitable rats (10%) resulted in reduction of active stress responses (act/pass = 0.35/0.5 instead of 1.0/0.4 in control). Hippocampus lesion in initially inhibited rats (30%) did not affect the basic pattern of psycho-emotional responses, while in the rats with initially depressed cognitive activity (60%) it resulted in decreasing of passive and increasing of active stress responses (act/pass = 0.45/1/4 instead of 0.3/1.9). The findings suggest that hippocampus takes part in the psycho-emotional responses while the individual psycho-emotional pattern is determined by the morpho-functional features responsible for organisation of a psycho-emotional condition.     

Behavioural, biochemical and histological effects of trimethyltin (TMT) induced brain damage in the rat.

To assess the nature and extent of behavioural, biochemical and histological changes induced by trimethyltin (TMT), rats were treated with a single injection of TMT over a dose range of 6, 7 and 8 mg/kg i.p. Behavioural observations were performed at a minimum of 21 days after the administration of TMT. The behavioural consequences of TMT were hyperactivity in the open-field test, increased locomotor activity and deficits in passive and active avoidance behaviour, T-maze alternation and Morris Water Maze behaviour. The behavioural changes were dose dependent and were accompanied by a degree of pathological damage to the hippocampal pyramidal cells which was particularly apparent at the highest dose. The main biochemical effects of TMT involved deficits in the serotonergic and GABA-ergic systems and a decrease in M1 and M2 binding sites in the hippocampus. These results suggest that the toxic interaction of TMT with the hippocampus and other limbic brain regions may be responsible for its effect on learning and memory.     

Innate forms of behavior and energy metabolism in the brain of the rat after phenazepam administration in the presence of inescapable painful stimulation

Initially low level of motor search activity in test situations ("open field", maze) in rats previously grouped according to their passive behaviour with a partner-victim (Simonov method), does not essentially change after 3-week administration of phenazepam; the activity level of cytochrome oxidase in the cortex and hypothalamus is lowered. Phenazepam administration in conditions of prolonged unavoidable painful stimulation brings to a sharp increase of motor search activity and aggressive behaviour. Simultaneously the cytochrome oxidase activity increases in the same way as during a stress without phenazepam. This fact points to the independence of behavioural and biochemical effects in this case.     

Changes in innate forms of motor behavior in rats during long-term hypokinesia

The structure of motor behaviour in response to environmental tests--"open field" and "with-a-partner" situation (according to P. V. Simonov)--was studied in rats after 1, 3 and 6 weeks of hypokinesis, (to K. Hecht), as compared to the control. In control animals a relatively low level of orienting-investigation reactions and of grooming was observed as well as a low alimentary activity, which is considered as a manifestation of innate passive defensive reactions in the above situations. Disappearance of these reactions in the course of hypokinesia has two stages: predominant increase in orienting-investigating reactions (1-3 weeks); their subsequent decrease and an increase in the grooming (after 6 weeks). The relation between innate and conditioned behavioural changes is discussed as well as stability of alimentary behaviour in rats.     

Progeny of male rats treated with methadone: physiological and behavioural effects

Male rats were injected with methadone HCl (METH) at 5 mg/kg s.c. for 4 days prior to mating with drug-free females. Offspring resulting from these matings were compared with offspring of drug-free males. The progeny of METH-treated males gained less weight after weaning and had lighter thymuses as adults (but not in infancy). Gonadal weights did not differ in infancy or adulthood, and adrenal weights were heavier in female offspring in adulthood. In adulthood METH offspring were significantly different from controls on all behavioural tests used (open field activity, activity cage activity, passive avoidance latencies, shuttle box avoidances, and rotarod latencies), with the differences frequently affected by test order, days of testing, or sex of offspring. The effects in progeny of METH-treated males in the absence of differences in litter size or neonatal mortality indicate that paternal drug ingestion prior to mating can produce physiological and behavioural changes in progeny that are not dependent on detectable effects on early viability or growth.     

An ethopharmacological analysis of morphine effects in fish (Macropodus Opercularis)

The behavioural effects of morphine on fish (Macropodus opercularis) were studied by an ethopharmacological analysis. For this purpose active and passive behavioural units were observed.The results show that morphine treatment had a stimulating effect. However, the treatment resulted not in a general enhancement of active behavioural units, but in a selective increase of some of them, such as swimming and erratic behaviour, or in stereotyped behaviours, such as circling. By contrast, high dosages of morphine resulted in a decrease of escape and of standing under the surface behaviours.     

Anti-stress activity of Indian Hypericum perforatum L

Indian Hypericum perforatum (IHp) was investigated on a 14-day mild, unpredictable and inescapable foot shock stress (FSS) induced perturbations in behaviour (depression), suppressed male sexual behaviour and cognitive dysfunction in albino rats. Gastric ulceration, and adrenal gland and spleen weights, were also used as the stress indices. Panax ginseng (PG) was used as the standard adaptogenic agent for comparison. FSS induced marked gastric ulceration, significant increase in adrenal gland weight with concomitant decrease in spleen weight. Chronic stress also suppressed male sexual behaviour, induced behavioural depression (Porsolt's swim despair test and learned helplessness test) and cognitive dysfunction (attenuated retention of learning in active and passive avoidance tests). All these FSS induced perturbations were attenuated dose dependently by IHp (100 and 200 mg/kg, po) and PG (100 mg/kg, po). The results indicate that IHp has significant anti-stress activity, qualitatively comparable to PG, against a variety of behavioural and physiological perturbations induced by chronic stress, which has been proposed to be a better indicator of clinical stress than acute stress, and may indicate adaptogenic activity.     

Changes in avoidance behaviour following ethanol treatment in rats of different ages

Avoidance learning and pain sensitivity were studied in rats after chronic ethanol administration (1.1 to 1.7 g per kg b.w. in drinking water) at prenatal, adolescent and adult ages. The behavioural reactions were tested in adulthood by studying passive and active avoidance learning and the threshold of pain sensitivity to electric tail shock. Chronic ethanol consumption led to an impairment of avoidance learning and to hyperalgesia in each experimental series, although the alterations were greater in the prenatally treated groups. The experimental observations are discussed in the light of fetal alcohol syndrome.