Functional laterality is known as an intrinsic property of the brain. Since several studies have shown the presence of laterality in many species other than humans, it has been suggested that this is an adaptive mechanism to aid survival. Previous studies have shown that lateralized behavior observed during exposure to different environmental stimuli is not constant in normal animals, depending on the geometrical form of the exploratory field. In these exploratory fields, animals showed right- or left-biased exploratory behavior, according to the nature of the geometrical properties of the environment. Previously, it was found that tellurium (Te) was able to block spontaneous left-biased exploration in one defined geometrical environment. In the present work, the influence of Te and selenium (Se) in animals exposed to novel geometrically different environments were studied. Three geometrically different testing fields (square, rectangle, and T-shaped) were presented to Se- and Te-treated groups of rats. The results show that in the square field, only the Se treatment was able to block spontaneous right-biased exploratory responses; in the rectangular field, both Se and Te treatments blocked right-biased exploratory responses, and in the T-shaped field, only Te was able to block spontaneous left-biased exploratory responses. Data suggest that trace elements modify lateralized behavioral responses independently of the form of the novel exploratory field, suggesting the presence of a specific action in the brain.
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Trace element and its probable role in biological systems have attracted the attention of many researchers in recent years. Previous work has shown that ZnTe administered in drinking water to pregnant rats during pregnancy, delivery, lactation and offspring maturation up to prepuberal stage is able to modify several parameters of spontaneous behaviours related to cognition in offspring rats. Since Zn and Te have many biological properties, it’s not possible to conclude if behavioural changes are due to Zn, Te or both trace elements activity. In the present work, K2TeO3 and ZnCl2 were used alone in order to evaluate single actions of trace elements. Four experimental groups were formed: Control (water), Zn-treated group, Te-treated groups, and Zn+Te group. At the end of the experiments at 30 days of age offspring of each group were tested individually in a Double-Hole Board Labyrinth to evaluate lateralized exploration. Open field enriched with a rack and hole-board to evaluate motivated exploration; single cage in an intruder-host test to evaluate social interaction, and forced swimming cylinder to evaluate the survival responses. Results showed selective changes in rearing for Te (first Test); blocking of the natural left-biased exploration (second Test) increased time to confront the intruder with decreased time to interact with the intruder (third Test), and decreased time to active swimming (fourth Test).
With the exception of duration of the social interaction, Zn has no effect. Results suggest that most of the behavioural changes found with ZnTe in previous studies are due to Te.