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Lizard as a potential behavioral model: comparison of exploratory behavior and brain catecholamine levels between Italian wall lizard and Wistar rat

Besides representing an important model for studies in the fields of conservation biology, ecophysiology and evolution, lizards may be interesting as a model in translational research for the elucidation of the underlying mechanisms of behavior and its adaptive value. The Italian wall lizard (Podarcis sicula) is a highly adaptable species that occupies a variety of habitats (the main area of distribution is Italy and the eastern Adriatic coast with surrounding islands) and undergoes population specific adaptations in morphology, physiology and behavior. In this study, we explored the potential of P. sicula as a model for exploratory behavior by comparing its behavioral and neurochemical parameters to those of the Wistar rat, a behavioral model well established in our Laboratory. Exploratory behavior of 28 lizards was analyzed in open field as time spent in movement, total distance travelled, percent of time spent in the central area, and number of rearings. The levels of dopamine (DA) and noradrenaline (NA) were determined in brain tissue homogenates of 20 lizards using the standard ELISA kit for human catecholamines. P. sicula displayed the whole spectrum of behavior in open field with comparable average number of rearings and % time in open space to those of rats. They spent more time in movement, with lower speed, travelling therefore less total distance than rats in a 10 min experiment. We were able to reliably measure catecholamine levels in 50x diluted whole-brain homogenates, and they amounted to 417 ± 116 pg/mg DA and 917 ± 170 pg/mg NA, which is about one order of magnitude higher than in rat brain cortex. Our results speak in favor of the use of P. sicula as a potential model for studying the neurochemical basis of behavioral adaptation in laboratory conditions.

lizard, rat, behavior, dopamine, noradrenaline

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