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PubMed2001

Behavioral tests of hippocampal function: simple paradigms complex problems.

Behavioral tests have become important tools for the analysis of functional effects of induced mutations in transgenic mice. However, depending on the type of mutation and several experimental parameters, false positive or negative findings may be obtained. Given the fact that molecular neurobiologists now make increasing use of behavioral paradigms in their research, it is imperative to revisit such problems. In this review three tests, T-maze spontaneous alternation task (T-CAT), Context dependent fear conditioning (CDFC), and Morris water maze (MWM) sensitive to hippocampal function, serve as illustrative examples for the potential problems. Spontaneous alternation tests are sometimes flawed because the handling procedure makes the test dependent on fear rather than exploratory behavior leading to altered alternation rates independent of hippocampal function. CDFC can provide misleading results because the context test, assumed to be a configural task dependent on the hippocampus, may have a significant elemental, i.e. cued, component. MWM may pose problems if its visible platform task is disproportionately easier for the subjects to solve than the hidden platform task, if the order of administration of visible and hidden platform tasks is not counterbalanced, or if inappropriate parameters are measured. Without attempting to be exhaustive, this review discusses such experimental problems and gives examples on how to avoid them.

Animals↗

PubMed2006

Cognitive aging in zebrafish.

BACKGROUND: Age-related impairments in cognitive functions represent a growing clinical and social issue. Genetic and behavioral characterization of animal models can provide critical information on the intrinsic and environmental factors that determine the deterioration or preservation of cognitive abilities throughout life. METHODOLOGY/PRINCIPAL FINDINGS: Behavior of wild-type, mutant and gamma-irradiated zebrafish (Danio rerio) was documented using image-analysis technique. Conditioned responses to spatial, visual and temporal cues were investigated in young, middle-aged and old animals. The results demonstrate that zebrafish aging is associated with changes in cognitive responses to emotionally positive and negative experiences, reduced generalization of adaptive associations, increased stereotypic and reduced exploratory behavior and altered temporal entrainment. Genetic upregulation of cholinergic transmission attenuates cognitive decline in middle-aged achesb55/+ mutants, compared to wild-type siblings. In contrast, the genotoxic stress of gamma-irradiation accelerates the onset of cognitive impairment in young zebrafish. CONCLUSIONS/SIGNIFICANCE: These findings would allow the use of powerful molecular biological resources accumulated in the zebrafish field to address the mechanisms of cognitive senescence, and promote the search for therapeutic strategies which may attenuate age-related cognitive decline.

Acetylcholinesterase↗

PubMed1990

Effects of toluene exposure during gestation on neurobehavioral development of rats and hamsters.

Pregnant rats and hamsters were exposed to toluene vapor (800 mg/m3) 6 h daily from gestation days 14 to 20, and 6 to 11, respectively. Growth, neuromotor development and performance of the offspring in behavioral tasks were assessed. In rats, toluene exposure increased the number of litters with low birth weight pups. Male rat offspring exposed to toluene displayed shorter latencies than male controls to choose one side of a T maze in a spontaneous alternation test. Hamsters exposed to toluene performed worse in a rotating rod test. These results confirm toluene fetotoxicity in rats and suggest an effect on exploratory behavior which may be related to hormonal changes in early life. Neuromotor effects of exposure of hamsters to toluene in utero deserve further investigation.

Animals↗

PubMed2000

Effect of antenatal exposure to Saint John's wort (Hypericum) on neurobehavior of developing mice.

OBJECTIVE: We conducted, in a randomized, placebo-controlled manner, behavioral testing on mice offspring exposed antenatally to the herbal antidepressant Saint John's wort (Hypericum ). STUDY DESIGN: A daily dose of Saint John's wort (0.75 mg/g of food consumed), equivalent to that in human beings according to body surface, was chosen because it has been shown to cause an antidepressant effect in adult mice. CD-1 mice were randomly assigned to consume either Saint John's wort (n = 45) or a placebo (n = 45) for 2 weeks before conception and throughout gestation. Behavioral testing consisted of early developmental tasks of geotaxis, separation vocalization, and homing, followed by motor, anxiety, and depression assessments into adulthood. RESULTS: Birth weights of male offspring were less in the Saint John's wort group than in the placebo group (1.68 vs. 1.75 g; P<.01). Offspring in both treatment groups showed no long-term statistical differences in early developmental tasks, locomotor activity, and exploratory behavior throughout development. Performances on a depression task (forced swim) and on anxiety tasks (elevated plus maze as juveniles and adults) revealed no differences between treatment groups. CONCLUSION: Antenatal exposure to a therapeutic dose of Saint John's wort showed no long-term deficits on selected behavioral tasks by developing mice offspring.

Animals↗

PubMed1983

Parental methadone treatment: a multigenerational study of development and behavior in offspring.

After 60 days of treating both sexes with daily oral doses of 15 mg/kg methadone hydrochloride, Wistar rats were mated. Drug treatment of females continued until the weaning of their pups. The body weight of pups was reduced compared to controls up to weaning, and viability was significantly decreased. Ontogeny of reflexes was delayed, and exploration in an open-field arena was reduced up to 2 weeks of age, but then increased above controls. Defecation in the open-field arena was lessened. When only the sire received methadone, only the increase in exploratory behavior and the decrease in defecation occurred. Breeding offspring (F1) of which both parents had methadone treatment gave F2 generation offspring for which neonatal mortality was significantly elevated and defecation in the open-field arena was lessened at 21 days. No changes clearly traceable to methadone were found in the subsequent F3 generation. Some F3 generation rats were treated with methadone and bred in the same manner as the original parental generation. The resulting pups, having the genealogy twice-exposed to methadone, were not significantly different from those whose immediate parents only received the drug.

Animals↗

PubMed1991

Behavioral development and maternal care in tufted capuchins (Cebus apella) and squirrel monkeys (Saimiri sciureus) from birth through seven months.

Fourteen infant capuchins and eight squirrel monkeys reared by their mothers in captive species-typical social groups were observed from birth through 7 months. Motoric altriciality of the neonatal capuchin relative to the squirrel monkey is a key feature of behavioral differences between the species in the first few months after birth. Infants of the two species differed substantially in age at onset of independent locomotion, the developmental profile of independent activities, and the overall amount and rate of particular social activities. Capuchins displayed a lag of 7 weeks relative to squirrel monkeys in the pattern of increasing time spent alone; lags in other indices of independent activity and exploratory behaviors were also evident, although not as clear-cut. The species also differed substantially in the nature and frequency of social interactions between infants and others. Capuchins, especially later-born infants of multiparous mothers, experienced a more socially interactive infancy than squirrel monkeys. Contrasts in behavioral developmental and infant care in the two species are related to the timing and duration of the weaning process.

Age Factors↗

PubMedDate not supplied

Effects of prenatal stress on defensive withdrawal behavior and corticotropin releasing factor systems in rat brain.

Exposure of pregnant rats to stress results in offspring that exhibit abnormally fearful behavior and have elevated neuroendocrine responses to novelty and aversive stimuli. This study examined the effects of prenatal stress on plasma corticosterone, adrenal weight, defensive withdrawal behavior, and the density of receptors for corticotropin releasing factor (CRF) in the amygdala. Pregnant Sprague-Dawley rats were stressed by daily handling and saline injection (s.c., 0.9%, 0.1 mL) during the last week of gestation. Male offspring were studied at adulthood (60-120 days of age). Adrenal hypertrophy and increased plasma corticosterone were observed in the prenatally stressed offspring. Defensive withdrawal, an ethological measure of the conflict between exploratory behavior and retreat, was quantified in naive offspring, and in offspring exposed to restraint stress (2 h). Restraint stress increased defensive withdrawal in both control and prenatally stressed offspring. Both naive and restraint-stressed prenatally stressed offspring exhibited increased defensive withdrawal compared to control offspring. There was a significant interaction between prenatal stress and restraint stress, suggesting increased vulnerability of prenatally stressed offspring. The effects of restraint in the defensive withdrawal test were reduced by intracerebroventricular administration of the CRF antagonists, alpha-helical CRF9-41 (20 microg every hour) or D-phe(12), Nle(21, 38), C(alpha)-MeLeu(37)]-CRF((12-41)) (5 microg every hour) during the restraint period. The difference between control and prenatally stressed offspring was abolished by the CRF antagonists, suggesting that increased activation of CRF receptors may be a factor in the behavioral abnormalities of prenatally stressed rats. Measurement of CRF receptors in amygdala revealed a 2.5-fold increase in binding in prenatally stressed offspring. In light of previous work from this laboratory demonstrating increased content and release of CRF in amygdala from prenatally stressed offspring, the present study suggests that the increased fearfulness of prenatally stressed rats may be a consequence of increased activity of CRFergic systems in the amygdala.

Adrenal Glands↗

PubMed2002

Angiotensin IV in the central nervous system.

The mammalian brain harbors a renin-angiotensin system (RAS), which is independent from the peripheral RAS. Angiotensin II is a well-studied member of the RAS and exerts most of the known angiotensin-mediated effects on fluid and electrolyte homeostasis, autonomic activity, neuroendocrine regulation, and behavior. This review summarizes a mass of compelling new evidence for the biological role of an active (3-8) fragment of angiotensin II, named angiotensin IV. Angiotensin IV binds to a widely distributed binding site in the brain, but which is different from the known angiotensin II receptors AT1 and AT2. Angiotensin IV has been implicated in a number of physiological actions, including the regulation of blood flow, the modulation of exploratory behavior, and processes attributed to learning and memory. Furthermore, angiotensin IV may also be involved in neuronal development. Collectively, the available evidence suggests that angiotensin IV is a potent neuropeptide, involved in a broad range of brain functions.

Angiotensin II↗

PubMed2002

Modulatory effects of norepinephrine, acting on alpha 1 receptors in the central nucleus of the amygdala, on behavioral and neuroendocrine responses to acute immobilization stress.

The central nucleus of the amygdala (CeA) is a component of the limbic fear-anxiety circuit, and has also been implicated in regulation of the hypothalamic-pituitary-adrenal (HPA) stress axis. The CeA receives dense noradrenergic innervation, and is rich in expression of alpha(1)-adrenergic receptors. We hypothesized that norepinephrine (NE), acting on alpha(1) receptors in CeA, may modulate stress-induced anxiety-like behavioral responses and HPA activation. To investigate the role of alpha(1) adrenergic receptors in CeA on stress-induced behavioral reactivity, the alpha(1) antagonist benoxathian was microinjected bilaterally into CeA of male Sprague-Dawley rats, and anxiety-like behavioral responses to acute immobilization stress were measured on the Social Interaction (SI) test and on the Elevated Plus-maze (EPMZ). Benoxathian dose dependently blocked the reduction in SI time induced by immobilization stress, whereas beta-receptor antagonists had no effect, consistent with an absence of beta-receptors in CeA. By contrast, in separate experiments, benoxathian had no effect on stress-induced reduction in open-arm exploratory behavior on the EPMZ, nor on stress-induced plasma ACTH secretion. These results confirm that the SI test and EPMZ measure different aspects of behavioral stress reactivity that can be modulated independently, and likewise, that noradrenergic modulation of behavioral stress reactivity can occur independently of modulation of the HPA axis.

Adrenergic alpha-1 Receptor Agonists↗

PubMed2001

Rat as model for studying behavior effects of hCG.

The demonstration of receptors for luteinizing hormone (LH)/human chorionic gonadotropin (hCG) in several parts of rat brain suggested their novel functional role. Subsequent studies tested the effect of hCG (intraperitoneally or intracerebroventricularly) on brain arousal and different types of stress situations in an intact female rat model on the day of proestrus. Treatment resulted in changes of activity and several other behavioral patterns associated with sites of brain hCG/LH receptors. hCG given peripherally caused a longer sleeping time and a decreased activity level. Whereas administration of indomethacin alone had no effect, coadministration inhibited the effects of hCG. hCG increased immunoreactive prostaglandin D2 (PGD2) and decreased PGE2 in brain areas controlling activity and sleep. hCG effects were probably mediated via prostaglandin pathways. After central hCG treatment, animals were less active and showed less exploratory behavior in an open-field box than the control animals. Taste and odor neophobias were dramatically decreased following central injection of hCG. hCG-treated rats were less anxious and exhibited a higher level of maternal interest than the controls. hCG treatment also had a beneficial effect against stress ulcer, which was prevented by pretreatment with antisense receptor oligonucleotide, suggesting a direct hCG receptor-mediated effect. In summary, because hCG can cross the blood-brain barrier, both peripheral administration and central administration affect several behavioral patterns. This effect is similar to treatment with anxiolytics and suggests the functional relevance of brain LH/hCG receptors. Some observed behavioral changes have parallels in pregnant women.

Animals↗

PubMedDate not supplied

[The effect of anosmia on sex dimorphism in the patterns of orienting-exploratory, emotional and passive defensive behaviors in rats].

Sex dimorphic patterns of exploratory behavior in the open-field, passive defensive behavior and emotionality were studied in anosmic rats. It was show that the long-time anosmia increased the level of exploratory and locomotor activities in male rats and changed their behavior in stress situations from passive to active form. Anosmia didn't change characteristics of these forms of behavior in female rats.

Animals↗

PubMed2002

Local application of L- threo-hydroxyaspartate and malonate in rats in vivo induces rigidity and damages neurons of the substantia nigra, pars compacta.

In order to study neuronal death in Parkinson's disease, neurons of the substantia nigra, pars compacta in rats were exposed to elevated levels of glutamate and decreased levels of energy in vivo and consequences for behavior and neuronal morphology were studied. Thus, repeated local injections (9x) of the glutamate uptake inhibitor L- threo-hydroxyaspartate (L-THA; 833 microM in 0.3 microl) in the presence or absence of the succinate dehydrogenase inhibitor malonate (25 mM in 0.3 microl) were applied during three weeks. 24 h after injection, rigidity and catalepsy were measured, as well as, at the end of the three week period, locomotion, rearing and exploratory behavior. Thereafter, the cytoarchitecture of the substantia nigra, pars compacta of the brains of these rats was described. The L-THA plus malonate injected rats did not differ in their behavior from carrier injected rats, except for rigidity: their scores were higher than that of carrier and L-THA injected rats (P < 0.05), while L-THA injected rats did not differ from carrier injected controls. Observations on cresyl violet sections revealed, that, although many neurons with a shrunken nucleolus and faintly stained cytoplasm were present in both L-THA and L-THA plus malonate treated rats, the ventral edge of the substantia nigra, pars compacta containing modified cells was longer in L-THA plus malonate than in L-THA injected rats (P < 0.05). This indicates, that a minimum amount of damage to neurons in the ventral part of the substantia nigra, pars compacta might be required for the expression of rigidity.

Animals↗

PubMed2005

In vivo inhibition of hippocampal Ca2+/calmodulin-dependent protein kinase II by RNA interference.

Hippocampal alpha-Ca2+/calmodulin-dependent protein kinase II (alpha-CaMKII) has been implicated in spatial learning, neuronal plasticity, epilepsy, and cerebral ischemia. In the present study, an adeno-associated virus (AAV) vector was designed to express green fluorescent protein (GFP) from the CBA promoter and a small hairpin RNA targeting alpha-CaMKII (AAV-shCAM) driven from the U6 promoter. The AAV-shCAM or control vector was microinfused into the rat hippocampus and behavioral testing conducted 19-26 days following surgery. Expression of the marker gene and alpha-CaMKII was evaluated 31 days following AAV infusion. GFP expression was localized to the hippocampus and extended +/-2 mm rostral and caudal from the injection site. Hippocampal alpha-CaMKII was significantly reduced following AAV-shCAM treatment as demonstrated using immunohistochemical and Western analysis. This suppression of alpha-CaMKII was associated with changes in exploratory behavior (open field task) and impaired place learning (water maze task). These results demonstrate the efficacy of a viral-based delivered shRNA to produce gene suppression in a specific circuit of the brain.

Animals↗

PubMed2004

Tracking whisker and head movements in unrestrained behaving rodents.

Due to recent advances that enable real-time electrophysiological recordings in brains of awake behaving rodents, effective methods for analyzing the large amount of behavioral data thus generated, at millisecond resolution, are required. We describe a semiautomated, efficient method for accurate tracking of head and mystacial vibrissae (whisker) movements in freely moving rodents using high-speed video. By tracking the entire length of individual whiskers, we show how both location and shape of whiskers are relevant when describing the kinematics of whisker movements and whisker interactions with objects during a whisker-dependent task and exploratory behavior.

Animals↗

PubMed1989

Modulatory effect of locus coeruleus stimulation on visually evoked potentials in freely moving rats.

Interactions between light-flash stimulation and electrical single impulse stimulation of locus coeruleus (LC) were investigated in 9 freely moving rats with chronically implanted electrodes during different behavioral states. The interaction of both showed different immediate and long-lasting effects. Simultaneous visual and electrical stimulation caused a clear decrease of trigger rate of photically evoked after-discharges from 60% to 15% and a reduction of the early primary component of visually evoked potentials (VEP) in area 17 compared with the values without LC stimulation during relaxed wakefulness (RW). On the contrary, the simultaneous LC stimulation was ineffective during exploratory behavioral states (E). At 100 ms stimulus interval and more there was no detectable LC stimulus effect on VEP components during RW, whereas the LC stimulation under beta-blockade (2.5 mg/kg propranolol i.p.) during RW-like behavior clearly reduced the early VEP component to 75% compared with values without LC stimulation. On the other hand, LC stimulation facilitated mainly the primary VEP component to about 160% during E compared with the flash response alone. This effect was observed from 100 to 300 ms after LC stimulus and was unaffected by muscarinic blockade (0.5 mg/kg scopolamine i.p.). We conclude from these data that the short-time effects are comparable with the influence of spontaneous behavioral activation and probably result from a costimulation of cholinergic neurons around LC, whereas the long-lasting effects may be attributed to the influence of noradrenergic LC cells. The noradrenergic-dependent facilitation of early VEP component counteracts the cholinergically-induced reduction.

Animals↗

PubMed1994

Behavioral evidence of trigeminal neuropathic pain following chronic constriction injury to the rat's infraorbital nerve.

Video recordings of free behavior and responses to mechanical facial stimulation were analyzed to assess whether chronic constriction injury (CCI) to the rat's infraorbital nerve (IoN) results in behavioral alterations indicative of neuropathic pain. A unilateral CCI was produced by placing loose chromic gut ligatures around the IoN. After CCI to the IoN, rats exhibited changes in both non-evoked and evoked behavior. Behavioral changes developed in two phases. Early after CCI (postoperative days 1-15), rats showed increased face-grooming activity with face-wash strokes directed to the injured nerve territory, while the responsiveness to stimulation of this area was decreased. Later after CCI (postoperative days 15-130), the prevalence of asymmetric face grooming was reduced but remained significantly increased compared to control rats. The early hyporesponsiveness was abruptly replaced by an extreme hyperresponsiveness: all stimulus intensities applied to the injured nerve territory evoked the "maximal" response (brisk head withdrawal, avoidance behavior plus directed face grooming). This response was never observed in control rats. Concurrently, IoN ligation rats showed a limited increase in the responsiveness to stimulation of the contralateral IoN territory, and around postoperative days 30-40 the responsiveness to stimulation of facial areas outside the IoN territories also increased. The hyperresponsiveness to stimulation of the ligated IoN territory slightly decreased from 60 d postoperative. Throughout the study, IoN ligation rats showed decreased exploratory behavior, displayed more freezing-like behavior, had a slower body weight gain, and a higher defecation rate, compared to control rats. The behavioral alterations observed after CCI to the IoN are indicative of severe sensory disturbances within the territory of the injured nerve: mechanical allodynia develops after a period of relative hypo-/anesthesia during which behavioral signs of recurrent spontaneous, aversive (possibly painful) sensations (paresthesias/dysesthesias) are maximal.

Animals↗

PubMed2006

EEG theta rhythm in infants and preschool children.

OBJECTIVE: To study behavioral correlates of theta oscillations in infants and preschool children. METHODS: EEG was recorded during baseline (visual attention) and two test conditions--exploration of toys and attention to 'social' stimulation. Age specific frequency boundaries of theta and mu rhythms were assessed using narrow bin analysis of EEG spectra. RESULTS: Theta spectral power increased whereas mu power decreased under test conditions in both age groups. In preschoolers theta rhythm increased predominantly over anterior regions during exploratory behavior and over posterior regions during attention to social stimulation. Theta frequency range changed with age from 3.6 to 5.6 Hz in infants to 4-8 Hz in children, and mu range from 6.4-8.4 Hz to 8.4-10.4 Hz. CONCLUSIONS: In early life, theta oscillations are strongly related to behavioral states with substantial attentional and emotional load. The scalp distribution of theta spectral power depends on age and behavioral condition and may reflect engagement of different brain networks in control of behavior. SIGNIFICANCE: The findings contribute to the scanty knowledge about the developmental course of theta rhythm. Data on behavioral correlates of theta rhythm in early life may improve our understanding of cognitive and mental processes in healthy and neuropsychiatrically diseased children.

Age Factors↗

PubMed2004

Effect of the ketogenic diet on the activity level of Wistar rats.

Children, adolescents, and adults with epilepsy often also show symptoms associated with attention-deficit/hyperactivity disorder (ADHD). The ketogenic diet, which is administered to children with epilepsy refractory to drug therapy, seems to improve behavior in individuals with symptoms of ADHD. The basis for this improvement is unknown, although it seems to be unrelated to seizure control. The present research was designed to investigate the effect of two ketogenic diets on the behavior of normal adult male rats. Two experiments were conducted. In experiment 1, 36 subjects were placed on one of three diets: a control diet, a 6.3:1 ketogenic diet, and a 4:1 ketogenic diet. In experiment 2, 20 subjects were placed either on a control diet or on a 4:1 ketogenic diet. The activity level of each subject was measured using an open field test. Time spent immobile, grooming, and in exploratory behavior was measured for 600 s. Subjects were tested once before initiation of the diets and once while on the diets. No significant group differences were found in activity level before initiation of the diets. After initiation of the diets, subjects in both ketogenic groups showed a significantly lower activity level than the rats on the control diet. The ketogenic diet decreases activity level in an animal model. This behavioral change may relate to the improved behavior seen when children with symptoms of ADHD are placed on the diet.

Adolescent↗