The elevated T-maze as a measure of two types of defensive reactions: a factor analysis

Consistency of cognitive performance in spatial navigation and its link to activity and boldness in laboratory rats

Even though cognitive testing in animals is widespread, many issues remain open - for example the influence of behavioural parameters on cognitive performance, stability of cognitive performance upon repeated testing, or comparability of cognitive variables across different tasks (i.e. cross-contextual consistency). In this study we tested thirty six male Long Evans laboratory rats and assessed their cognitive performance in two standard tasks of spatial navigation - Active allothetic place avoidance and Morris water maze test. Using multivariate analyses, we detected different aspects of cognition within these complex tasks (the ability to learn fast, cognitive flexibility, general ability to solve a task successfully). We found that consistency of cognitive performance in these two tasks (estimates of cognitive repeatability) differed substantially, reflecting differences in the experimental procedures. Moreover, we inspected cognitive performance of the animals in more detail by creating a correlation matrix of factors derived from these procedures. Nevertheless, we found no correlation and therefore no indication of a general cognitive ability in spatial navigation using these two tasks. In addition, we found no link between personality and cognition when correlating cognitive performance of the animals with parameters from personality tests, which were derived from a previous study conducted on the same animals. These findings highlight a task-dependent nature of cognitive performance in these two tasks of spatial navigation and suggest that general cognitive ability in spatial navigation may not be reliably inferred from these two tasks, while also indicating no evident link between cognition and personality in this context.

Structural consistency of exploratory behaviour of sub-adult and adult spiny mice (Acomys cahirinus) in seven different tests

The genus Acomys is of growing importance to many research fields. Previous research has shown that individuals differ when exploring new environments and that these behavioural strategies are consistent in time. In this study, we subjected 60 commensal Acomys cahirinus (37 males, 23 females) to a series of seven tests (free exploration, forced exploration under bright illumination, forced exploration under low illumination, hole board test, vertical activity test, elevated plus maze, and voluntary wheel running) to acquire independent behavioural traits and investigate whether and how personality develops in spiny mice. The full series of experiments was performed twice during ontogeny: once in the sub-adult stage (tested at 62-72 days of age) and once in the adult stage (102-112 days of age). We found that behaviour of the animals was repeatable both within (range of R values from 0.155 to 0.726) and across the two life-stages (0.238 to 0.563). While the structure of behaviour in adults was rather clear, it had not been fully crystalized in sub-adults, suggesting personality changes during maturation, even though some individual traits might be repeatable across ontogeny. Notably, the most consistent behavioural traits across the different tests were jumping and rearing, which are not commonly reported.

Inter-individual differences in laboratory rats as revealed by three behavioural tasks

Stable inter-individual differences in behaviour and personality have been studied for several decades now. The aim of this study was to test the repeatability of behaviour of the Long Evans strain of laboratory rats in order to assess their inter-individual differences. Male laboratory rats (n = 36) were tested in a series of tasks (Open field test, Elevated plus maze test, and modified T-maze test) repeated over time to assess their personality traits. To evaluate the temporal stability of the behaviour, we calculated repeatability estimates of the examined traits. We also checked for a link in behavioural traits across these experiments, which would suggest the existence of a behavioural syndrome. We found stable inter-individual differences in behaviour. Interestingly, no link emerged between the tasks we studied and therefore we did not find support for a behavioural syndrome. The lack of behavioural correlations between these experiments suggests that the results derived from these tasks should be interpreted carefully, as these experiments may measure various behavioural axes. Moreover, the animals habituate to the apparatus. Consequently, behaviour in the Open field test and Elevated plus maze test is not fully consistent and repeatable across subsequent trials.

Behavioral models in psychopathology: epistemic and semantic considerations

The use of animals in neurosciences has a long history. It is considered indispensable in areas in which “translational” research is deemed invaluable, such as behavioral pharmacology and comparative psychology. Animal models are being used in pharmacology and genetics to screen for treatment targets, and in the field of experimental psychopathology to understand the neurobehavioral underpinnings of a disorder and of its putative treatment. The centrality of behavioral models betrays the complexity of the epistemic and semantic considerations which are needed to understand what a model is. In this review, such considerations are made, and the breadth of model building and evaluation approaches is extended to include theoretical considerations on the etiology of mental disorders. This expansion is expected to help improve the validity of behavioral models and to increase their translational value. Moreover, the role of theory in improving construct validity creates the need for behavioral scientists to fully engage this process.

Role of TRPV1 receptors on panic-like behaviors mediated by the dorsolateral periaqueductal gray in rats

The transient receptors potential vanilloid type 1 channels (TRPV1) are expressed in several brain regions related to defensive behaviors, including the dorsolateral periaqueductal gray (dlPAG). The endocannabinoid anandamide, in addition to its agonist activity at cannabinoid type 1 (CB1), is also proposed as an endogenous agonist of these receptors, through which it could facilitate anxiety-like responses. The aim of this work was to test the hypothesis that TRPV1 in the dlPAG of rats would mediate panic-like responses in two models, namely the escape responses induced by chemical stimulation of this structure or by exposure to the elevated T-Maze (ETM). Antagonism of TRPV1 with capsazepine injected into the dlPAG reduced the defense response induced by local NMDA-injection, suggesting an anti-aversive effect. In the ETM, capsazepine inhibited escape response, suggesting a panicolytic-like effect. Interestingly, this effect was prevented by a CB1 antagonist (AM251). The present study showed that antagonism of TRPV1 in the dlPAG induces panicolytic-like effects, which can be prevented by a CB1 antagonist. Therefore, these antiaversive effects of TRPV1 blockade may ultimately occur due to a predominant action of anandamide through CB1 receptors.

Maladaptive defensive behaviours in monoamine oxidase A-deficient mice

Rich evidence indicates that monoamine oxidase (MAO) A, the major enzyme catalysing the degradation of monoamine neurotransmitters, plays a key role in emotional regulation. Although MAOA deficiency is associated with reactive aggression in humans and mice, the involvement of this enzyme in defensive behaviour remains controversial and poorly understood. To address this issue, we tested MAOA knockout (KO) mice in a spectrum of paradigms and settings associated with variable degrees of threat. The presentation of novel inanimate objects induced a significant reduction in exploratory approaches and increase in defensive behaviours, such as tail-rattling, biting and digging. These neophobic responses were context-dependent and particularly marked in the home cage. In the elevated plus- and T-mazes, MAOA KO mice and wild-type (WT) littermates displayed equivalent locomotor activity and time in closed and open arms; however, MAOA KO mice featured significant reductions in risk assessment, as well as unconditioned avoidance and escape. No differences between genotypes were observed in the defensive withdrawal and emergence test. Conversely, MAOA KO mice exhibited a dramatic reduction of defensive and fear-related behaviours in the presence of predator-related cues, such as predator urine or an anaesthetized rat, in comparison with those observed in their WT littermates. The behavioural abnormalities in MAOA KO mice were not paralleled by overt alterations in sensory and microvibrissal functions. Collectively, these results suggest that MAOA deficiency leads to a general inability to appropriately assess contextual risk and attune defensive and emotional responses to environmental cues.

Spatial memory: Theoretical basis and comparative review on experimental methods in rodents

The assessment of learning and memory in animal models has been widely employed in scientific research for a long time. Among these models, those representing diseases with primary processes of affected memory - such as amnesia, dementia, brain aging, etc. - studies dealing with the toxic effects of specific drugs, and other exploring neurodevelopment, trauma, epilepsy and neuropsychiatric disorders, are often called on to employ these tools. There is a diversity of experimental methods assessing animal learning and memory skills. Overall, mazes are the devices mostly used today to test memory in rodents; there are several types of them, but their real usefulness, advantages and applications remain to be fully established and depend on the particular variant selected by the experimenter. The aims of the present article are first, to briefly review the accumulated knowledge in regard to spatial memory tasks; second, to bring the reader information on the different types of rodent mazes available to test spatial memory; and third, to elucidate the usefulness and limitations of each of these devices.