Exploratory activity

An increased level of exploratory activity immediately after exposure, attributed to reduced anxiety on the part of the rats, was also observed in this study. Decreased avoidance was observed in rats exposed to 125 ppm trichloroethylene 4 hours per day, 5 days per week for 30 days (Goldberg et al. 1964a). Changes in visually evoked potentials (Blain et al. 1992) and electroretinal responses to flash stimulation (Blain et al. 1994) were seen in rabbits exposed to 350 ppm trichloroethylene for 12 weeks (4 days/week, 4 hours/day). The study authors suggested that binding of trichloroethanol to blood proteins may enable it to reach the visual cortex. 

Most of these models evaluate the effects of drugs on the behaviour of animals when they are exposed to a novel environment. Novelty normally reduces animals exploratory activity but established anti-anxiety drugs consistently increase exploration of, and approaches to, the novel stimulus and reduce the neophobic ( avoidance ) reaction. There are several examples of tests based on this principle (Table 19.2) but two that are widely used are the plus-maze and the social interaction tests. 

Adams, L. M. (1983) LSD-induced alterations in spatial and temporal patterns of exploratory activity. Doctoral dissertation. University of California at San Diego, San Diego, California. 

Rat (Sprague- Dawley) 9 wk (W) 13 M decreased litter weight and exploratory activity Mobley et al. 1990 Chlorine dioxide... 

Likewise, mechanisms responsible for the developmental effects observed in laboratory animals exposed to chlorine dioxide or chlorite are not known. They might be related to the oxidative properties of these chemicals. Although overt signs of neurodevelopmental effects (delays in exploratory activity and general locomotor activity) and altered serum th5Toid hormone have been observed concurrently in animals that had been exposed via their mothers during pre and postpartiun development, a mechanistic basis has not been investigated. 

Studies in mice with a targeted inactivation of other 5-HT receptor sub-types, such as the S-HTsa and 5-HT7, or a transgenic line that overexpresses 5-HT3, demonstrate that these receptors modulate the activity of neural circuits involved specifically in exploratory and reward-related behavior. When exposed to novel environments, KO mice lacking the S-HTsa exhibit increased exploratory activity and an attenuated stimulatory effect of lysergic acid diethylamide (LSD) on exploratory activity but no change in anxiety-related behavior (Grailhe et al. 1999), whereas S-HTy KO mice do not express any overt behavioral phenotype at all (Hedlund et al. 2003). 

Gorman JM, Kent JM, Sullivan CM, Coplan JD (2000) Nemoanatomical hypothesis of panic disorder, revised. Am J Psychiatry 157 493-505 Grailhe R, Waeber C, Dulawa SC, Hornung JP, Zhuang X, Brunner D, Geyer MA, Hen R (1999) Increased exploratory activity and altered response to LSD in mice lacking the 5-HT(5A) receptor. Neuron 22 581-591... 

The behavior of tacl mice was also analyzed in several animal models of anxiety. The open-field test is a widely used tool for behavioral research, but less specific for the evaluation of the anxiety state of the animal, because it is a summation of the spontaneous motor and the exploratory activities, and only the latter is influenced by the anxiety level (Choleris et al. 2001). Under aversive environmental conditions (high level of illumination) the animals activity is strongly affected by the emotional state, while less aversive situations (familiar, dimly lit environment) are useful to assess the general motor activity of mice. Because rodents avoid open areas, the activity of mice in the central part of the open-field arena is inversely correlated to the anxiety level. Tad mice spent only 6.5% of their total activity in the central part, which represented 11% of the total field, indicating that they avoided this aversive area, hi contrast, tacl mice spent 13.6% of their activity in the central area (Bilkei-Gorzo et al. 2002). The increased central activity of the tad mice indicates that the test situation was anxiogenic for tad animals, but less so for the knockout mice. 

Although there is evidence that A3AR ko mice are more prone to depressive behavior, it is also reported that they have increased performance in the elevated-plus maze and light/dark box suggestive of reduced anxiety but this is most probably a consequence of the increase in exploratory activity due to increased motor activity (Fedorova et al. 2003). 

Ackermann GE, Marenholz I, Wolfer DP, Chan WY, Schafer B, Erne P, Heizmann CW. 2006. S100A1-deficient male mice exhibit increased exploratory activity and reduced anxiety-related responses. Biochim Biophys Acta - Molecular Cell Research, in press. 

Kitazawa T, Hashiba K, Cao J, Unno T, Komori S, Yamada M, Wess J, Taneike T (2007) Functional roles of muscarinic M2 and M3 receptors in mouse stomach motility studies with muscarinic receptor knockout mice. Eur J Pharmacol 554 212-22 Knauber J, Muller WE (2000) Decreased exploratory activity and impaired passive avoidance behaviour in mice deficient for the aiB-adrenoceptor. Eur Neuropsychopharmacol 10 423-7 Koshimizu TA, Tanoue A, Tsujimoto G (2006) Clinical implications from studies of oti adrenergic receptor knockout mice. Biochem Pharmacol. 

Grailhe R, Waeber C, Dulawa SC, et al. Increased exploratory activity and altered response to LSD in mice lacking the 5-HT5A receptor. Neuron 1999 22 581-591. 

Malleret G, Hen R, Guillou JL, Segu L, Buhot MC. 5-HT1B receptor knock-out mice exhibit increased exploratory activity and enhanced spatial memory performance in the Morris water maze. J Neurosci 1999 19(14) 6157-6168. 

In a 1957 review, he noted, A certain apathy and slowness of reaction have been frequent symptoms in the experimental animals. Or, as he remarked in a later review (Schou, 1976), there is decreased spontaneous and exploratory activity. ... 

These studies show that memory-guided foraging in the radial maze is related to activity in a distributed network including the hippocampal formation (ventral subiculum), which sends direct projections to the NAc shell and to the prelimbic PFCX, which in turn directly projects to the NAc. DA, acting on Dl receptors, modulates the trasfer of information at two critical sites, the PFCX and the NAc. In the PFCX, DA enables the prospective use of delayed spatial information. In the NAc, DA enables the retrospective use of spatial information acquired during exploratory activity. 

Zalcman SS (2001) Interleukin-2 potentiates novelty—and GBR 12909-induced exploratory activity. Brain Res 899 1-9. 

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