Subject emotionality and subsequent pylorus ligation-induced or restraint-induced gastric ulcer

Rats were tested for “emotionality” in a standardized open-field procedure for four consecutive days. In one experiment, open-field testing was followed by a 24-hour period of starvation and by a 10-hour period of pyloric occlusion. In a second study, open-field testing was followed by 12 hours of starvation and by three hours of supine restraint-cold (4–6° C). “High-emotional” and “low-emotional” animals differed significantly in terms of glandular ulcers (both experiments) and gastric secretion (Experiment 1). Low-emotional animals had less gastric damage and secreted a smaller volume of less concentrated gastric acid. Discriminant analysis indicated that the behavioral measures of open-field defecation and open-field ambulation were the best discriminators of high and low emotionality. Multiple regression analysis also suggested that open-field defecation and ambulation were good predictors of gastric glandular ulceration induced by either pyloric ligation or stress due to supine restraint-cold.     

Correlative effects of psychogenetic selection: A study of the roman high and low avoidance strains of rats

A sample of 86 rats of the RHA and RLA strains, selectively bred in Rome for speed of acquisition of conditioned avoidance responses (CAR), was given the open-field test of emotionality, and re-tested for conditioning in their new environment. Both sexes were included in a balanced-order design. The standardized open-field test and a conventional shuttle-box with buzzer as the conditioned stimulus and shock as the unconditioned stimulus were used. The results show that the Roman strains do not differ in respect of open-field defecation. While the RHA strain was confirmed as superior in measures of CAR formation, it was also found to be significantly more active both in the open-field (ambulation) and in inter-trial activity during conditioning. No effects attributable either to order of test administration or the previous history of the subjects were detected, and those due to their sex merely confirmed previous findings. These results are contrasted with the findings for the Maudsley strains of reactive and non-reactive rats which differ significantly in respect of emotional elimination as a result of a similar selection procedure, but which also display a similar difference in CAR acquisition and in mature body weight.     

Sensitivity to low doses of ethanol and pentobarbital in mice selected for sensitivity to hypnotic doses of ethanol.

These experiments assessed sensitivity to low doses of ethanol and pentobarbital in mice that had been selectively bred with respect to ethanol sleep time (the length of time an animal remains on its back following a hypnotic dose of ethanol). The hypothesis under investigation was that short-sleep (SS) mice might be more sensitive than long-sleep (LS) mice to excitatory effects produced by low doses of depressants. In support of this hypothesis SS mice were more active in an open-field test after ethanol than were LS mice. The lines did not differ in performance on a rotating-rod apparatus after these same doses of ethanol, suggesting that the difference in open-field activity was not attributable to a greater impairment of locomotor activity in LS mice. A similar difference in the open-field activity of the selected lines was observed with pentobarbital.     

An ethological analysis of open-field behavior in rats and mice

In our view open-field testing entails both a predatory encounter, which occurs as a consequence of handling and placement of subjects into the testing apparatus, and sudden social separation from conspecifics. We hypothesize, therefore, that open-field behavior represents a compromise between responses aimed at minimizing detectability as a predator evasion tactic, and those which are motivated by attempts to reinstate contact with companions. Six experiments were conducted using rats and mice to test various implications of this model. Pretest shock and the presence of a human observer each retarded the appearance of social reinstatement behaviors and enhanced responses which minimize detectability in both species. Likewise, because of diminished reinstatement tendencies animals tested in pairs froze longer than those tested individually. The applicability of this model to other aspects of open-field behavior in rodents was examined, and the contrast between this view and the general emotionality hypothesis was briefly discussed.     

Mice selectively bred for open-field thigmotaxis: life span and stability of the selection trait

In 2 experiments, the authors examined 69 mice selectively bred for high or low levels of open-field (OF) thigmotactic behavior (high open-field thigmotaxis [HOFT] and low open-field thigmotaxis [LOFT], respectively). They found that the strains differed in defecation during the 60-min exposure to the OF. Furthermore, the strains differed with regard to their life spans: The more thigmotactic HOFT mice lived longer than the LOFT mice. The strains were not differentiated by food intake or excretion. The strain difference in thigmotaxis was not age dependent, and it persisted in the home-cage condition as well. Neither the location (center or wall) of the starting point nor the shape (circular or square) of the OF arena affected the difference in wall-seeking behavior between the two strains. The authors concluded that the difference in thigmotaxis (or emotionality) between the HOFT and LOFT mice is a stable and robust feature of these animals.     

EXPERIMENTS CONCERNING THE TRANSFER OFA LEARNED RESPONSE AND ACTIVITY LEVEL BY BRAIN HOMOGENATES

L agerspetz , K. M. J., R aitis , P., T irri , R. & L agerspetz , K. Y. H. Experiments concerning the transfer of a learned response and activity level by brain homogenates. Scand.J. Psychol ., 1968, 9, 225–229,— The learning of a conditioned avoidance response caused an increase in the open-field activity of male albino mice. Pseudo-conditioning had an opposite effect. The transfer of brain homogenate from the trained animals did not facilitate the acquisition of the avoidance response by the recipient animals. Differences in the open-field activity were not transmitted with the brain homogenates. However, the constancy of the open-field activity scores was decreased by the homogenate injection, and also by severe electric shocks.     

Open-field behavior of spontaneously hypertensive and Wistar-Kyoto normotensive rats: effects of reciprocal cross-fostering

The influence of the maternal environment on the development of open-field behavior in spontaneously hypertensive (SHR) rats was investigated using the technique of reciprocal cross-fostering. Entire litters of SHR and Wistar-Kyoto (WKY) normotensive rats were either reared by their natural mothers, in-fostered to dams of the same strain, or cross-fostered to dams of the opposite strain on the day after birth. Open-field behavior was assessed in male and female rats from the six groups (2 strains x 3 rearing conditions) at 30, 60, 90, and 120 days of age. Animals were observed in the open-field during a 5-min test period and the number of squares entered and hindlimb rears were recorded. At all ages tested, SHR rats were more active in the open field, entering more squares and rearing more frequently than WKYs. SHR females were more active than age-matched SHR males, while no sex differences were apparent in the WKY strain. At each age, open-field behavior was similar across WKY rearing groups. SHR control and in-fostered animals responded similarly in the open field; however, SHR cross-fostered rats (particularly females) tended to be more active than controls. Although cross-fostering has profound effects on cardiovascular development and functioning in the SHR, it appears that altering the early maternal environment experienced by SHR pups does not grossly affect the development of open-field behavior.     

Cardiovascular responses to open-field stress in rats: sex differences and effects of gonadal hormones

We studied sex differences in cardiovascular responses to stress using a new radio-telemetry model in which freely-moving Spontaneously Hypertensive rats (SHR) are exposed to open-field novelty stress. This model allowed simultaneous assessment of cardiovascular and behavioural responses to psychological stress. Female SHR in the diestrous stage of their estrous cycle had markedly greater pressor and tachycardic responses to open-field exposure when compared to either female rats not in diestrous or male SHR. Treatment of ovariectomized SHR with estrogen alone had no significant effect on cardiovascular reactivity, while a combined treatment of estrogen and progesterone slightly, but significantly attenuated their pressor response to open-field stress. In addition, treatment of castrated male rats with testosterone significantly enhanced their pressor responses to stress when compared to values obtained before treatment. None of the hormone treatments had any significant effect on heart rate responses to stress. Neither at different stages of the estrous cycle nor after hormone treatments were there any marked changes in behavioural responses in the open-field, making it unlikely that the differences in cardiovascular stress responses were caused by changes in behavioural activity. These data demonstrate differences in cardiovascular stress responses that seem to be dependent on the stage of the estrous cycle. They suggest that particularly androgens, such as testosterone, may enhance pressor responses to stress. On the other hand, a combination of estrogen and progesterone, rather than estrogen alone, may have a small attenuating effect on cardiovascular reactivity.     

Open-Field Foraging: The Influence of Prior Taste-Aversion Conditioning

The Psychological Record - Two experiments evaluating open-field foraging behavior of rats that had received prior taste aversion conditioning to liquid saccharin are reported. In both studies each...     

Locomotor, avoidance,and maze behavior in rats with selective disruption of hippocampal output.

Behavioral correlates of selective disruption of hippocampal output were investigated in a series of five experiments. In two experiments an attempt was made through behavioral investigation to determine whether the CA1 neurons project to the fimbria or to the subiculum. The results supported recent views that the subiculum is the recipient of CA1 axons. Disruption of the CA1 output in the dorsal hippocampus of rats produced increased open-field activity, whereas passive avoidance and spontaneous alternation behaviors remained unchanged. No differentiation was obtained between CA1 damage and neocortical lesions in maze learning. Blocking of the fimbrial CA3 output from the dorsal hippocampus improved passive avoidance performance and impaired active avoidance performance, whereas open-field and spontaneous alternation behaviors were unaffected. Interruption of the CA3 output from the ventral hippocampus improved active avoidance performance and reduced spontaneous alternation behavior. Open-field behavior and passive avoidance performance remained unchanged. Total fimbrial sections increased open-field activity, improved passive and active avoidance, and reduced spontaneous alternation. The results are discussed in terms of functional differentiation between the CA1 and CA3 of the dorsal hippocampus and in terms of functional differences in the fimbrial CA3 output from the dorsal and ventral hippocampus.     

The stability and interest consonance of lateral postural--motor biases in rats: results and implications

Each of six different tests of lateral postural-motor asymmetries was repeatedly administered to 126 rats. Directional reliability was found for rotatory swimming, open-field exploration, and stepping down from a beam. Neonatal posture, turn in an unbaited T maze, and orientation to tail pinch proved not to be reliable across days. The behavioral asymmetries in the open-field and step-down tests were directionally consonant with each other, but neither was related to the asymmetry exhibited in rotatory swimming, implying the existence of at least two independent asymmetrical neural substrates underlying the behaviors. Neither sample-wide directional biases nor major sex differences in bias were found. The sexes were, however, differentially influenced in direction on some tests by the number of males in their natal litters, implying a role for intrauterine exposure to androgens in predisposing rats toward some left- or right-biased behaviors.     

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 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.     

A theory of behavior in a two-valenced psychoecological space

A theory of behavior in a two-valenced psychoecological space is presented. It is an extension of Miller's theory of approach-avoidance mechanisms into a two-dimensional space. It incorporates a learning theory, which describes how the approach and avoidance gradients are built up following experiences over time. It also includes a choice model for an individual's action within the space. The theory describes an organism as active in its psychoecological space, interacting with the environment. The theory is explicated mathematically with a combination of algebraic and stochastic functions and simulated on a computer parallel to an illustratory experimental example with the behavior of rats in an open-field situation with positive reinforcement and punishment at different spatial positions. Examples from simulations with different learning and choice parameters are given together with examples of the changing approach and avoidance surfaces. The predicted behavior patterns are compared with empirical findings in the open-field observations, and the results are used to determine plausible sets of parameter values for the different experimental conditions.     

Aggressive behavior inhibition by serotonin and quipazine injected into the amygdala in the rat

The effects on aggressive behavior, open-field activity, and pain threshold of bilateral microinjections of serotonin (20 micrograms) and quipazine (20 micrograms), the direct serotonergic receptor agonist, into the cortico-medial amygdala were investigated in Wistar rats. Both drugs significantly prolonged the attack latency in isolated killer rats (predatory aggression model), and suppressed the incidence of aggressive postures/attacks in shock-induced fighting test (affective aggression). The only difference in the open-field behavior was the lower number of central square entries in drug-treated compared to saline-injected rats. None of the substances produced any significant change in jump threshold. It is concluded that stimulation of serotonin receptors within the amygdala produces inhibition of affective and muricidal behavior in isolated rats. The effect does not seem to be dependent on changes in general activity and pain sensitivity.     

Stress ulcer and open-field behavior of spontaneously hypertensive,normotensive, and Wistar rats

Spontaneously hypertensive rats (SHRs) and the normotensive Wistar/Kyoto (WKY) rat were observed, along with Wistar rats (which represent the parent strain), on various open-field behaviors. All three strains were subsequently exposed to the activity-stress (A-S) ulcerogenic procedure. SHR and Wistar rats were very active in most open-field measures as compared with WKY rats, but only SHRs were active during the A-S treatment. WKY rats were very ulcer prone and had significantly more ulcers than SHRs, which in turn had more ulcers than Wistar rats. It was anticipated that Wistar rats would resemble the WKY rats, but in most measures the Wistars resembled the SHRs. The study suggests that although WKY rats function as an appropriate control for hypertension studies, these rats may be inappropriate as controls for other physiological and behavioral studies.     

Effects of intrahippocampal injections of the cholinergic neurotoxin AF64A on open-field activity and avoidance learning in the rat

The effects of direct intrahippocampal administration of the cholinergic neurotoxin, AF64A, were investigated in male rats. Bilateral injections of AF64A (5 nmole/2 microliters) produced a significant decrease in choline acetyltransferase (CAT) activity in the dorsal hippocampus (25%) and overlying frontoparietal cortex (30%) but no changes in the striatum. Rats lesioned with AF64A exhibited increased levels of open-field activity, which was most marked at 1 week after the lesion; however, the rates of intrasession habituation were similar in lesioned and control rats. Lesioned rats also displayed deficits in acquisition and retention of a passive avoidance task and less dramatic deficits in acquisition of two-way shuttle box avoidance. These findings indicate that lesioning of cholinergic terminals in the hippocampus and/or cerebral cortex with AF64A leads to long-term deficits in learning and memory as well as increases in open-field activity.     

Goal-tracking behavior in the pond snail, Lymnaea stagnalis

The occurrence of goal-tracking, an unconditioned stimulus (US)-directed autoshaping behavior, was studied in open-field tests with control and classically conditioned pond snails, Lymnaea stagnalis. In an appetitive classical conditioning paradigm with a tactile stimulus as conditioned stimulus (CS) and a localized food stimulus as US a conditioned feeding response built up in the experimental but not in the control animals. In the post-training open-field tests the experimental group alone showed an enhanced attraction toward the source of water current in the environment which previously signalled the arrival of the US but did not act as CS in the classical conditioning procedure. We suggest that this stimulus-directed goal-tracking behavior in Lymnaea is the result of a classical-operant interaction, described so far only in vertebrate animals, and that neurophysiological analysis of this behavior is possible in this snail.     

Differential effects of environmental enrichment on the open-field behavior of wild and domestic Norway rats.

Early postweaning experience in an enriched environment had a greater influence on the open-field behavior and body weight of wild Norway rats than of their domestic counterparts. Genetic changes accompanying the domestication process may have reduced the relative impact of postweaning experience on the development of the domestic rat's response to changes in its environment.     

An automated open-field apparatus utilizing an improved resistance detection circuit

An open-field apparatus that can be automatically operated is described. Detection of movement is electronic and based upon the fact that the S will complete a circuit path when crossing an open field. The circuit is very sensitive yet quite immune to the usual problem of 60-Hz interference.     

A small step for rats alters spatial behavior: rats on a bi-level arena explore each level separately

Animal Cognition - We tested rats on a ‘bi-level open-field’ whose two halves were separated vertically by an 8-cm step that the rats could easily ascend/descend. We sought to determine...