Rats In Open Field Research Articles

Effects of illumination and handling upon rat open field activity

Eighty male rats (Crj:CD, 4 weeks old), were randomly assigned to four groups in a 2 x 2 (brightness x handling) factorial design. Ambulation and three types of defecations [pre-open-field defecation (PRD), post-open-field defecation (POD), and testing defecation (TD)] were examined for 3 consecutive days, for 3 min per day. In this study, the effects of handling treatment were illumination dependent. The changes in TD and POD were opposite in relation to the trial day, whereas the changes during the trial, the sum of the TD and POD, were invariable. Considering the invariable changes of the sum of TD and POD, time per trial may be an important factor to measure emotional activity. The TD-POD inversion may reflect the strength of the stress response against a novel placement in open field, because of the change of the time for evoking defecation behavior.

Subdiaphragmatic vagotomy does not prevent the anti-exploratory effect of caerulein in the elevated plus-maze

We compared the action of subdiaphragmatic vagotomy upon the anti-exploratory and motor depressant effects of caerulein, an agonist of cholecystokinin (CCK) receptors, in male rats. Vagotomized rats entered more frequently into the open arms of elevated plus-maze compared to intact control rats. Caerulein (1 μg/kg subcutaneously (s.c.)) significantly suppressed the exploratory behaviour in vagotomized rats but not in intact and sham-operated rats. In contrast, subdiaphragmatic vagotomy did not change the locomotor activity of rats in open field compared to intact and sham-operated animals. At a higher dose (10 μg/kg s.c.), the caerulein pretreatment markedly decreased the number of line crossings, rearings and head-dippings of intact animals in open field. In sham-operated rats caerulein also suppressed the locomotor activity, whereas in vagotomized rats it only tended to reduce the frequency of rearings. Consequently, the present study revealed the different action of vagotomy upon the motor depressant and anti-exploratory effects of caerulein. These results support the view that CCK A receptors in the gastrointestinal tract are mediating the motor depressant, whereas CCK B receptors in the brainstem are involved into the mediation of anti-exploratory effect of caerulein.

Lesions in four parts of the basal forebrain change basic behaviour in rats.

Subdivisions of the basal forebrain (BF) are postulated to be differently involved in the regulation of behavioural functions. We compared 16 parameters of rat open field behaviour before, 10 days and 60 days after lesions in four BF subdivisions, the anterior and the posterior nucleus basalis magnocellularis (NBMa, NBMp), the vertical and the horizontal diagonal band nucleus (VDB, HDB) with sham-operated control rats. Every lesion type caused a significantly different pattern of significant behavioural changes. VDB and NBMp lesions both produced different patterns of ambulatory and exploratory hyperactivity, whereas NBMa lesions caused hypoactivity. Changes after HDB lesions were relatively small. The rate of habituation also shared changes that differed according to the lesion site. These changes in basic unlearned behaviour are likely to interact with more complex functions such as cognitive processes, learning and memory.

Ro15-4513 antagonizes depression of open-field horizontal activity by ethanol in rats

The imidazobenzodiazepine, Ro15-4513, has been shown to antagonize some of the behavioral effects of ethanol (ETOH). In rats having relatively little experience in the open field, the actions of ETOH (0.75 g/kg IP), Ro15-4513 (1.25 mg/kg and 2.5 mg/kg, IP), and Ro15-4513 in combination with ETOH were measured on horizontal activity. Rats receiving ETOH showed a significant depression in horizontal activity. Doses of Ro15-4513 given alone produced no significant differences in activity from baseline levels. Rats pretreated with Ro15-4513 prior to receiving ETOH, however, showed a significant attenuation of the ETOH induced depression of activity. These results indicate that Ro15-4513 is effective in attenuating the depressive effects of ETOH in the open field in rats having little experience in the apparatus.

Another look at amphetamine-induced stereotyped locomotor activity in rats using a new statistic to measure locomotor stereotypy

Rat open field behavior is often used as a tool to study the behavioral effects of drugs. In this report, drug-induced patterns of locomotion in an open field were studied with the aid of a simple new statistic. Briefly, the animal's path through the open field is converted into a series of trips. Gamma (gamma) estimates the probability that the animal will repeat the trip that it has just exhibited; thus gamma quantifies "locomotor stereotypy". Trip lengths can also be compared across drug groups. Thus caffeine has no effect on gamma even though it produces a dose-related increase in locomotions. Caffeine does not produce amphetamine-like stereotypy. On the other hand, amphetamine produces a dose-related increase in gamma. Although gamma was designed to detect any pattern of locomotor behavior, rats treated with high doses of amphetamine almost always exhibited the same pattern of locomotor behavior - repetitive trips around the perimeter of the open field. Although further characterization of the statistic is necessary, these findings suggest that gamma has potential for quantifying "locomotor stereotypy" and for providing a more subtle description of locomotor behavior in general.

Effect of angiotensin II and saralasin on motor activity and the passive avoidance behavior of rats

One nmole of angiotensin II (ANG II) or saralasin, given intracerebroventricularly, failed to alter the motor activity of rats in open field. A combined injection of both peptides caused a significant decrease of the number of crossings and rearings. In the electromagnetic motimeter horizontal activity of animals was changed by neither of the peptides while the vertical activity was increased by ANG II. Again, a combined injection of saralasin and ANG II inhibited both horizontal and vertical activity. Stereotypies evoked by both apomorphine (2 mg/kg) and amphetamine (6.5 mg/kg), given intraperitoneally, were markedly intensified by ANG II and saralasin. A five-fold increase of the re-entry latencies in the passive avoidance situation was observed after pre-test administration of ANG II or saralasin but not the two in combination. These results suggest that ANG II and saralasin may improve processes related to learning and memory through an unspecific mechanism involving central dopamine systems.

Behavioral effects of angiotensin II and angiotensin II-(4-8)-pentapeptide in rats

One nM of angiotensin II (AII) or angiotensin II-(4–8)-pentapeptide [AII(4–8)] given intracerebroventricularly did not affect locomotor and exploratory behavior of rats in open field. AII significantly increased and AII(4–8) did not affect vertical activity of animals in electromagnetic motimeter. Neither of the peptides influenced horizontal activity in the motimeter. Both peptides intensified stereotypy produced by apomorphine and amphetamine. AII significantly improved, while AII(4–8) did not affect, consolidation of memory of the correct way to food in T-maze. Similarly, AII increased and AII(4–8) did not change the rate of acquisition of conditioned avoidance responses in a shuttle-box. Of the two examined peptides only AII significantly improved retrieval of memory of the passive avoidance behavior. The results show that AII(4–8) influences central dopaminergic system but, unlike its parent peptide AII, has no apparent effect on memory.

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.

A stimulatory effect of intraaccumbens injections of noradrenaline on the behavior of rats in the forced swim test.

Intraaccumbens injections of catecholamines noradrenaline and dopamine, though not of serotonin, stimulated locomotion by rats in an open field, 10-15 min later. Similar effects were observed 5 min after microinjection of apomorphine whereas clonidine only attenuated locomotor activity. On the other hand, intraaccumbens administration of phenylephrine, isoproterenol and quipazine, in doses similar to an effective dose of noradrenaline, did not alter rat open field behavior. The escape-directed activity of rats in the forced swim test (FST) was stimulated 5 min after local administration of noradrenaline, phenylephrine, isoproterenol or apomorphine only. No effects in the FST were observed 15 min after noradrenaline injection or after intracaudate noradrenaline administration. The stimulatory effects of intraaccumbens noradrenaline injection in the FST were antagonized by the local pretreatment of rats with phentolamine, though not with propranolol. Accordingly, it is possible to conclude that both catecholamines, but not serotonin, play complex and probably distinct roles within the nucleus accumbens in the stimulation of activity by rats in the FST and the open field test.

The effects of response-reinforcer contingency on time allocation in the open field

The present experiment explores the effects of the response (1-sec occupancy of a target area in an open field)—reinforcer (intracranial stimulation) contingency on time allocation in the open field in rats. The probability of reinforcement given a response ( X) and the probability of reinforcement given the absence of a response ( Y) were varied randomly across sessions within a subject. The following ( X, Y) values were utilized: (.05, 0), (.15, 0), (.25, 0), (.15, .05), and (.15, .15). The results of this experiment indicate that rate of acquisition of time allocation preference is uniformly rapid during all contingency treatments wherein Y = 0 and is negatively related to the value of Y when X = .15. The relationship between the asymptote of the time allocation acquisition function and the value of X (when Y = 0) is positively sloped and negatively accelerated, while the relationship between asymptote and the value of Y (when X = .15) is negatively sloped with zero acceleration. Proposed contingency metrics are evaluated.

Correlations between rats' spatial location and intracranial stimulation administration affects rate of acquisition and asymptotic level of time allocation preference in the open field

The present experiment explores the effects of the response (1-sec occupancy of a target area in an open field)-reinforcer (intracranial stimulation) contingency on time allocation in the open field in rats. The probability of reinforcement given response ( X) and the probability of reinforcement given nonresponse ( Y) were varied randomly across sessions within a subject. The 21 contingency treatments explored included all possible combinations of values (0, .1, .2, .3, .4, .5) of X and Y such that X ≥ Y. The results indicate that rate of acquisition and asymptotic level of time allocation preference to the target area are negatively related to the value of Y (for any given value of X). Variations in X (for any given value of Y) were less effective. Evaluation of proposed contingency metrics revealed that the Weber fraction (X − Y) X most closely approximates performance, and that the value of the difference detection threshold derived from the Weber fraction is a constant.

Locomotor activity of rats in open field after microinjection of procaine into superior colliculus or underlying reticular formation

Whereas large lesions of the superior colliculus in rats increase locomotor activity in the open field, bilateral collicular microinjections of muscimol (an agonist of the inhibitory neurotransmitter GABA) have been reported to reduce open-field activity. This difference might be due to muscimol's acting on a subpopulation of collicular neurones, or to some feature of the microinjection technique. The issue was investigated by observing open-field behaviour after reversible lesions produced by bilateral microinjections of the local anaesthetic procaine (10–300 μg in 0.5 μl) into midbrain sites. Injections of procaine into the superior colliculus produced effects similar to those reported after muscimol injections: both locomotor activity and other exploratory responses were suppressed, with the rats spending much of their time motionless in an alert posture. In contrast, animals with injections of procaine into the mesencephalic reticular formation (MRF) ventral to the superior colliculus resembled rats given large collicular lesions: they showed very striking increases in locomotor activity, while their rearing and exploratory head movements were reduced. It is suggested that in some experiments large collicular lesions may have increased locomotor activity in the open field because they invaded underlying MRF. However, it is also possible that in rodents the acute effects of collicular inactivation, as assessed by microinjection of muscimol or procaine, are different from the chronic effects that are observed in experiments with electrolytic or radiofrequency lesions.

Detailed analysis of the effects of apomorphine and d-amphetamine on spontaneous locomotor behaviour of rats as measured in a TV-based, automated open-field system

Rat open field behaviour was measured in a TV-based, automated system. Habituation was evident in saline-treated rats. Most variables measured declined over a 10 min period. Apomorphine affected rat open-field behaviour bimodally, i.e. low doses of apomorphine (0.02–0.08 mg/kg, s.c.) decreased most aspects of rat open-field behaviour, whereas at higher doses (0.2 and 0.5 mg/kg, s.c.) various aspects of open-field behaviour were stimulated. Rearing and average speed, however, were monotically depressed. Amphetamine (1 and 2 mg/kg) stimulated most aspects of rat open-field behaviour, including rearing. Speed was not affected by amphetamine. Habituation was more pronounced after low doses of apomorphine than after saline treatment and was absent after high doses of apomorphine and after amphetamine. The results represent a detailed analysis of apomorphine and amphetamine effects on rat open-field behaviour and show that the distinct components of this behaviour are affected differentially.

Potentiation by Des-Tyr-γ-endorphin of apomorphine-induced changes in rat open field behaviour

Des-Tyr-γ-endorphin in doses up to 10 μg per rat potentiated dose-dependently the effects of low (0.01 and 0.02 mg/kg s.c.) doses of apomorphine on rat open field behaviour as measured in an automated, TV-based system. Changes in rat open field behaviour induced by 0.2 mg/kg apomorphine, a threshold stimulating dose, were however not influenced by the peptide except for starts, which were antagonized. The peptide itself had no effect on open field behaviour. The present results parallel the earlier reported potentiation of low apomorphine-induced behavioural and neurochemical effects and suggest a modulatory effect of the peptide on dopaminergic activity.

Effects of single and long-term haloperidol administration on open field behavior of rats.

The effects of single and long-term haloperidol administration on rat open field behavior was studied. Withdrawal from long-term haloperidol treatment induced a significant increase in all parameters of activity recorded, except rearing. There was a direct relationship between the impairment of motor function induced by the single haloperidol administration and the increment of general activity observed after withdrawal from repeated drug administration. The results were considered to be a consequence of the supersensitivity of central dopaminergic receptors probably, of the mesostriatal pathway, that occurred in order to maintain the animal's homeostasis.

Effects of abrupt and gradual withdrawal from long-term haloperidol treatment on open field behavior of rats.

The effects of abrupt and gradual withdrawal from long-term haloperidol treatment on rat open field behavior was studied. Abrupt withdrawal induced a significant increase in all parameters of activity observed except defecation, this increase being higher 72 h after the last haloperidol injection. Results were considered to be a consequence of supersensitivity of central dopaminergic receptors. These differences were almost unobservable in animals gradually withdrawn, thus suggesting that the phenomenon is reversible.

Reduction by propranolol of raised urinary output of MHPG in hyperactive rats

Prolonged isolation of rats resulted in hyperactivity in the open field and a significant increase in 24 hr urinary excretion of MHPG (3-methoxy-4-hydroxyphenylglycol). Exploratory activity of group-housed rats in open field was not associated with raised MHPG excretion, compared with that of rats remaining in home cages. Exposure of group-housed rats to 4°C for 2 hr also increased urinary excretion of MHPG. Pretreatment of isolated rats with dl-, d-propranolol or practolol abolished hyperactivity of isolated rats and reduced MHPG output in these rats and in rats exposed to cold. dl-Propanolol did not reduce activity of grou-housed rats in open field or their urinary excretion of MHPG. It is suggested that propranolol may have a selective inhibitory effect on stress-induced increases in noradrenaline turnover.