Rats In Open Field Test Research Articles

Open field behavior and habituation in rats irradiated on the head with gamma-rays

The goal of this work was to establish the effects of irradiation of the head with gamma-rays on selected forms of innate behavior, as well as on the habituation process to new environment in the open field test in rats. During a 5-day control period behavioral parameters reflecting motoric and explorative activities, as well as anxiety (6 parameters in total) were followed daily in 20 male Sprague-Dawley rats in an open field. Fourteen animals were repeatedly tested after irradiation of the head with a single dose of 10 Gy of gamma-rays. The results showed statistically significant depression of motoric and explorative activities during the first 3 days after irradiation in comparison with the control period. After irradiation the level of anxiety was elevated. Habituation to a new environment was observed in non-irradiated, but not in irradiated animals. These results suggest that the applied dose of ionizing radiation influenced the brain centers involved in control of innate behavioral functions connected with response to a new environment in rats.

Acute treatment with low doses of memantine does not impair aversive, non-associative and recognition memory in rats

Memantine is a non-competitive N-methyl-d-aspartate receptor antagonist, which has been employed in the clinic as a neuroprotective agent for the treatment of several dementias, particularly Alzheimer's disease. In this study, we evaluated pharmacological effects of the acute administration of memantine on memory process. Memory retention scores were evaluated in normal adult Wistar rats injected with saline and memantine (2, 5, 10, and 20 mg/kg, IP) and then subjected to the step-down inhibitory avoidance task, habitation to an open-field apparatus, and object recognition task. The treatment with higher doses of memantine (10 and 20 mg/kg) injected 60 min before or immediately after training-session impaired acquisition and retention of aversive memory in the inhibitory avoidance task. In addition, higher doses of memantine injected 60 min before the first open-field exposure also impaired habituation during the second exposure to the apparatus. No significant differences were observed in the performance of rats treated with memantine, in all doses tested, compared to saline-treated rats in the object recognition task. Notably, we observed that at 5 mg/kg, memantine increased spontaneous locomotion and exploration in the rat open-field test. In conclusion, present findings support the view that memantine at lower doses did not affect memory formation in normal rats, but at high doses memantine, induce hyperlocomotion, which could bias the interpretation of the animal behavior assessed in memory tests.

Effects of bemitil and benzimidazole on behavior of rats in open-field test

Under conditions of the open-field test, we demonstrated that bemitil and benzimidazole injected intraperitoneally into rats in doses of 50 to 150 mg/kg suppress horizontal and vertical (motor and research) activities, as well as decrease the frequencies of episodes of grooming, defecation, and urination. Possible mechanisms underlying modifications of behavioral phenomena triggered by the above agents are discussed.

The influence of NMDA, a potent agonist of glutamate receptor, on behavioral activity of rats with experimental hyperammonemia evoked by liver failure

The study was designed to investigate the effects of NMDA receptor agonist on the behavioral activity in rats with experimental hyperammonemia. The experiments were performed on adult male Wistar rats. Experimental hyperammonemia was induced by intraperitoneal injections of tioacetamide (TAA, 200 mg/kg) for three consecutive days. Rats treated with saline (0.9%) served as control. Stimulation of the NMDA glutamatergic receptor was evoked by ip. injection of agonist N-methyl-D-aspartate acid (NMDA) in a dose of 30 mg/kg thirty minutes before experiments. Memory motivated affectively was evaluated in the passive avoidance responses. The speculative influence of the treatment on anxiety and motor activity was tested in elevated plus-maze and in open field respectively. To show change of NMDA receptor function after various doses of agonist, the seizures evoked by N-methyl-D-aspartate acid was carried out. This experiment showed that with rise of dose of NMDA time to appear of convulsions was contracted in rats with hyperammonemia as well as in control rats. Dose of NMDA caused convulsions was three times as less in rats with hyperammonemia than dose in control. Time of duration of convulsions was proportional to applied dose of NMDA and it lengthened with rise of agonist's dose in both groups of studied animals. Furthermore, we observed that NMDA increased motor activity of control rats in open field test, but not in rats with hyperammonemia (treated tioacetamide). Hyperammonemia did not have significant influence on motor activity and on a passive avoidance latency. The NMDA given in control and in hyperammonemia, increased acquisition, consolidation and recall of a passive avoidance responses. Moreover, NMDA had anxiogenic-like profile in elevated plus-maze. In rats with hyperammonemia NMDA had no influence on locomotor activity but it significantly increased memory in a passive avoidance responses. Furthermore, we observed that reactivity of NMDA glutamate receptor in rats with hyperammonemia was higher than in control rats.

New arylpiperazine 5-HT(1A) receptor ligands containing the pyrimido[2,1-f]purine fragment: synthesis, in vitro, and in vivo pharmacological evaluation.

New 1H,3H-pyrimido[2,1-f]purine-2,4-dione derivatives of arylpiperazine (11-22) were prepared and evaluated in vitro for their affinity for 5-HT(1A), 5-HT(2A), alpha(1), and D(2) receptors. The tested compounds showed high affinity for 5-HT(1A) and alpha(1) receptors (K(i) = 1.1-87 and 10-62 nM, respectively) and moderate to low affinity for 5-HT(2A) (K(i) = 56-881 nM) and D(2) receptors (K(i) = 94-1245 nM). Compounds 14, 15, 18, 19, and 21, mostly 3'-chlorophenylpiperazine derivatives, can be classified as mixed 5-HT(1A)/5-HT(2A)/alpha(1) ligands. Compound 13, which showed the highest 5-HT(1A) receptor affinity (K(i) = 1.1 nM), was 50-fold selective in relation to alpha(1) adrenoceptors and at least 250-fold over 5-HT(2A) and D(2) sites. On the basis of in vivo functional tests, 8-phenylpiperazinoethylamino (11), 8-(2'-methoxyphenylpiperazino)ethylamino (13), and 8-phenylpiperazinopropylamino (14) derivatives of 1,3-dimethyl-1H,3H-pyrimido[2,1-f]purine-2,4-dione were identified as potent pre- and postsynaptic 5-HT(1A) receptor antagonists. 1,3-Dimethyl-7-bromo-8-(phenylpiperazinopropylamino)-1H,3H-pyrimido[2,1-f]purine-2,4-dione (20) behaved like an agonist of presynaptic and as a partial agonist of postsynaptic 5-HT(1A) receptors and resembled ipsapirone in terms of functional intrinsic activity. It revealed marked anxiolytic-like activity in the Vogel test in rats, comparable to that of the reference drug diazepam, and exhibited antidepressant-like activity in the Porsolt test in rats. The sedative effect of 20, evaluated in the open field test in rats, appeared at doses twice as high as those inducing a minimal anxiolytic-like effect and was similar to the effects of diazepam.

Intermittent Exposure to Social Defeat and Open-field Test in Rats: Acute and Long-term Effects on ECG, Body Temperature and Physical Activity

This study investigated the effects of exposure to an intermittent homotypic stressor on: (i) habituation of acute autonomic responsivity (i.e. cardiac sympathovagal balance and susceptibility to arrhythmias), and (ii) circadian rhythmicity of heart rate, body temperature, and physical activity. After implantation of a transmitter for the radiotelemetric recording of electrocardiogram (ECG), body temperature and physical activity, adult male rats ( Rattus norvegicus, Wild Type Groningen strain) were repeatedly exposed (10 consecutive times, on alternate days) to either a social stressor (defeat by a con-specific, n =15 ) or an open-field, control challenge (transfer to a new cage; n =8 ). ECGs, body temperature and physical activity were continuously recorded in baseline, test and recovery periods (each lasting 15 u min), at the 1st and 10th episodes of both defeat and open-field challenge. The circadian rhythms of heart rate, body temperature and physical activity were monitored before (5 days), during (16 days) and after (21 days) the intermittent stress protocol. This study indicates that there is no clear habituation of either acute cardiac autonomic responsivity (as estimated by means of time-domain indexes of heart rate variability) or arrhythmia occurrence to a brief, intermittent, homotypic challenge, regardless of the nature of the stressor (social or non-social). On the other hand, rats exposed to social challenge also failed to show adaptation of acute temperature and activity stress responsiveness, whereas rats facing open-field challenge developed habituation of activity and sensitization of temperature responses. Repeated social challenge produced remarkable reductions of the heart rate circadian rhythm amplitude (this effect being significantly greater than that produced by intermittent open-field), but only minor changes in the daily rhythms of body temperature and physical activity.

The effects of dopamine D2 receptor ligands on novelty‐induced behavior in the rat open field test

To determine the potential role of dopamine D2 receptor in mechanisms of anxiety, the effects of the preferential dopamine D2 receptor agonist, quinpirole, and antagonists, haloperidol and (–) sulpiride, were examined, in comparison to the action of the preferential dopamine D3 receptor agonist, (±)7-OH-DPAT and d-amphetamine, in the rat open field test. The effects of dopamine D2 receptor ligands in active doses were additionally verified in the Vogel conflict procedure. Quinpirole at the lower dose of 1.0 mg/kg produced a selective anti-thigmotactic effect, and increased the number of entries into the central part of the open field, without any influence on animals motility. At this dose the drug also increased punished but not free drinking. Both haloperidol and (–) sulpiride reduced the number of entries into the central sector of the open field without changing rat motor activity. (–) Sulpiride in a dose-dependent manner decreased also the time spent in the central part of the open field. No effect of the antipsychotics was observed in the Vogel conflict test. (±)7-OH-DPAT failed to exert any action in the open field test, except the general inhibitory effect at the highest dose examined. d-Amphetamine increased rats ambulation without any effect on exploratory behavior. The data are discussed in relation to the role of changes in dopaminergic activity in modulation of anxiety, and relative importance of dopamine D2 receptor mechanisms.

The effects of dopamine D2 receptor ligands on novelty-induced behavior in the rat open field test

To determine the potential role of dopamine D2 receptor in mechanisms of anxiety, the effects of the preferential dopamine D2 receptor agonist, quinpirole, and antagonists, haloperidol and (–) sulpiride, were examined, in comparison to the action of the preferential dopamine D3 receptor agonist, (±)7-OH-DPAT and d-amphetamine, in the rat open field test. The effects of dopamine D2 receptor ligands in active doses were additionally verified in the Vogel conflict procedure. Quinpirole at the lower dose of 1.0 mg/kg produced a selective anti-thigmotactic effect, and increased the number of entries into the central part of the open field, without any influence on animals motility. At this dose the drug also increased punished but not free drinking. Both haloperidol and (–) sulpiride reduced the number of entries into the central sector of the open field without changing rat motor activity. (–) Sulpiride in a dose-dependent manner decreased also the time spent in the central part of the open field. No effect of the antipsychotics was observed in the Vogel conflict test. (±)7-OH-DPAT failed to exert any action in the open field test, except the general inhibitory effect at the highest dose examined. d-Amphetamine increased rats ambulation without any effect on exploratory behavior. The data are discussed in relation to the role of changes in dopaminergic activity in modulation of anxiety, and relative importance of dopamine D2 receptor mechanisms.

Inhibition of amphetamine- and apomorphine-induced behavioural effects by neuropeptide Y Y 1 receptor antagonist BIBO 3304

Neuropeptide Y (NPY) has an important role in the regulation of stress responses and feeding behaviour. There is evidence that some effects elicited by NPY occur due to modulation of action of regular neurotransmitters. The main objective of the present study was to test behavioural effects of the novel neuropeptide Y (NPY) Y 1 receptor antagonist (R)-N-[[4-(aminocarbonylaminomethyl)-phenyl]methyl]-N 2-(diphenylacetyl)-argininamide trifluoroacetate (BIBO 3304) on dopamine-dependent behaviour. Intracerebroventricular administration of BIBO 3304 (1, 10, 50 nmol) had no effect on locomotor activity as measured by number of rearings and number of squares visited in an open field test in rats, but at 50 nmol dose defecation was significantly increased. BIBO 3304 (10 nmol) reduced amphetamine-induced increases in horizontal and vertical activity whereas its S-configurated enantiomer BIBO 3457 was inactive. In an open field test BIBO 3304 (10 nmol) inhibited purposeless running in rats sensitized to direct dopaminergic agonist apomorphine (0.5 mg/kg, s.c.). BIBO 3304 (10 nmol but not 1 nmol, i.c.v.) reduced fighting in apomorphine-induced aggression paradigm. Apomorphine-induced aggression was reduced by another, structurally similar, but less potent NPY Y 1 receptor antagonist BIBP 3226 (10 nmol, i.c.v.). A lower dose of BIBP 3226 (1 nmol, i.c.v.) was inactive. Concomitant administration of BIBO 3304 (10 nmol) with low doses of apomorphine (0.5 mg/kg s.c.) over the course of 10 days failed to prevent the development of apomorphine-induced aggressiveness. These data demonstrate that behavioural response to indirectly (amphetamine) and directly (apomorphine) acting dopaminergic stimulants is inhibited by NPY Y 1 receptor antagonists and suggest that NPY Y 1 receptor activation might be important in pathophysiology of disorders associated with hyperactivity of dopaminergic pathways, such as psychosis, schizophrenia and drug abuse. We propose that the effects of BIBO 3304 on amphetamine/apomorphine-induced locomotion and apomorphine-induced aggressiveness are due to modulation of postsynaptic dopaminergic responses rather than direct effects of NPY Y 1 receptor antagonists on dopamine or NPY release.

Anxiogenic-like effect of the NPY Y 1 receptor antagonist BIBP3226 administered into the dorsal periaqueductal gray matter in rats

Exogenous neuropeptide Y (NPY) administered intracerebroventricularly or into the central nucleus of amygdala has anxiolytic-like effects in animal models of anxiety. These effects are probably mediated by the NPY Y 1 receptor. The role of the NPY Y 1 receptor activation by endogenous NPY in this and other brain areas has not been fully elucidated. The selective NPY Y 1 receptor antagonist (R)- N 2-(diphenylacetyl)- N-[(4-hydroxy-phenyl)methyl]- d-arginine amide (BIBP3226) was microinjected into various brain sites implicated in the regulation of anxiety-related behaviour and resultant behavioural changes were assessed using the elevated plus-maze (EPM) and open-field test in rats. Intracerebroventricular application of BIBP3226 (5.0 μg) which caused an anxiogenic-like effect in the EPM did not affect exploratory activity in the open-field test. A decrease in EPM exploration was observed also when BIBP3226 (0.5 μg) was microinjected into the dorsal periaqueductal gray matter (DPAG). Intra-DPAG BIBP3226 did not change open-field behaviour suggesting that the effects of BIBP3226 in the EPM test were not related to changes in locomotor activity in general. Bilateral application of BIBP3226 into the central nucleus of amygdala (0.5 and 2.5 μg/side) and unilateral injections into the locus coeruleus and the paraventricular nucleus of the hypothalamus (both 0.5 μg) were ineffective in modifying the plus-maze exploration. These data suggest that endogenous NPY may regulate anxiety-related behaviour in rats by acting via the NPY Y 1 receptors in DPAG.

Behavioral and Adrenocortical Responses to Open-Field Test in Rats Selected for Reduced Aggressiveness Toward Humans

Plyusnina, I. and I. Oskina. Behavioral and adrenocortical responses to open-field test in rats selected for reduced aggressiveness toward humans. Physiol Behav 61(3) 381–385, 1997.—Effects of domestication of Norway rats on their open-field behavior and the response of the pituitary-adrenal system were studied by comparing domesticated and wild gray rats that had been selected for 42 generations for reduction and maintenance of aggressive behavior toward humans. Basal corticosterone level and adrenal weight were also determined at the advanced selection. No significant differences in behavior (with the exception of rearing number) and corticosterone level were found between domesticated and wild rats on the first day of testing. The second encounter with a novel situation revealed differences in both behavioral and hormonal responses between 2 compared rat lines. The results obtained are considered from the veiwpoint of their similarity to, or difference from, the data available in the literature on comparison of laboratory and wild rats in the open-field test. The difference between the laboratory rats and those selected by us for reduced aggressiveness seems to be due to the fact that breeding at this stage is done not only for reduced aggressiveness, but also for increased exploratory activity.

Adrenocortical Response to Open-field Test in Rats with Anterodorsal Thalami Nuclei Lesion

The influence of limbic anterodorsal thalami nuclei (ADTN) on adrenocortical activity and on emotional reactivity were investigated in male and female rats. The emotional reactivity was evaluated by means of the open-field test and the corticoadrenal function by means of plasma and adrenal corticosterone concentration. The results demonstrate that ADTN lesion does not affect the behavioural patterns in the open-field test on the 29th and 30th day after lesion nor adrenal response when animals are exposed to a novel situation.

Differential open field reactivity in HAS and LAS rats

To identify potential differences in emotional reactivity in high (HAS) and low (LAS) alcohol-sensitive rats in open field tests, 20 ethanol naive, 19th generation HAS and 20 LAS rats from the University of Colorado's Alcohol Research Center each received three consecutive daily 20-min exposures to a 1-sq m open field. The results of repeated-measures ANOVA and Keuls tests, performed on each of five concurrently recorded behaviors, indicated that, compared to HAS rats, LAS animals exhibited significantly greater latencies to begin ambulation, elevated ambulation, and rearing scores that failed to habituate over 3 days, and an increasing intersession bolus count. In addition, significant positive correlations occurred between days 2 + 3 (but not day 1) ambulation and bolus counts in LAS but not HAS rats, and between day 1 ambulation and (i) rearings and (ii) center square entries in HAS but not LAS rats. Together with other cited data, these results provide support for a hypothesis of relatively greater emotional reactivity in LAS rats and illustrate the need for multiple measures and sessions in evaluating open field behavior.

A comparative study of the effects of ritanserin (R 55 667) and chlordiazepoxide on rat open field behavior

AbstractA rat open field test is described in which the inherent tendency of rats to explore an environment is titrated against their inherent tendency to avoid an open field that is large, brightly illuminated, ceilingless, and novel. The procedure appeared responsive to the effects of benzodiazepines, barbiturates, and some related compounds. Particularly pronounced activity was obtained with ritanserin; the compound disinhibited rat exploratory behavior at doses ranging from 0.04 to 10 mg/kg. Ritanserin, but not chlordiazepoxide, significantly increased the number of animals entering the open field. Chlordiazepoxide, but not ritanserin, significantly increased the number of animals making at least nine transits. The observations suggest that chlordiazepoxide and ritanserin differ in their mode of disinhibitory action on rat open field behavior.

Open-field Test in Rats with Microcephaly Induced by Prenatal Methylazoxymethanol Application

Open-field Test in Rats with Microcephaly Induced by Prenatal Methylazoxymethanol Application