Thigmotactic responses in an open-field

The goal of the present study was to investigate the role of thigmotaxis (the tendency to remain close to vertical surfaces) in rat exploratory behavior in an open-field. Thigmotaxis was investigated in a parametric way, using 24 experimentally adult naive male Wistar rats (210-230 g). Exploratory behavior was studied in an open-field (N = 12) in 5-min sessions and behavior was analyzed in terms of where it occurred: in areas surrounded by two, one, or no walls. Another group of rats (N = 12) was studied in an open-field with blocks placed near two of the corners so as to make these corner areas surrounded by three walls. The floor of the open-fields was divided into 20-cm squares in order to locate the exact place of occurrence of each behavior. The following behaviors were recorded: entries into the squares, rearings, and groomings. In both types of open-field the rats chose to remain longer in the squares surrounded by the largest possible number of walls. In one of the open-fields, the mean time (seconds) spent in squares surrounded by two walls was longer than the time spent in squares surrounded by one or no walls (37.2, 7.7, and 1.8 s, respectively). In the other open-field, the mean time spent in squares surrounded by three walls was longer than the time spent in squares surrounded by two, one or no walls (41.7, 20.4, 7.0, and 2.6 s, respectively). Other measures presented a similar profile. These results indicate that rats are sensitive to the number of walls in an environment and prefer to remain close to them

Anxiolytic-like effects observed in rats exposed to the elevated zero-maze following treatment with 5-HT₂/5-HT₃/5-HT₄ ligands

The present study examined the effects of administering selective 5-HT antagonists and agonists to rats tested in the elevated zero-maze (EZM) model of anxiety. The EZM paradigm has advantages over the elevated plus-maze (EPM) paradigm with respect to measuring anxiety, yet has been utilized less frequently. Three experiments were conducted each with a diazepam control (0.25, 0.5 and 0.75 mg/kg). In the first experiment, we administered the 5-HT(2C) antagonist RS 102221 (0.5, 1.0, and 2.0 mg/kg) and 5-HT(2C) agonist MK-212 (0.25, 0.5 and 0.75 mg/kg); in the second experiment, we administered the 5-HT(3) antagonist Y-25130 (0.1, 1.0 and 3.0 mg/kg) and 5-HT(3) agonist SR 57227A (0.1, 1.0 and 3.0 mg/kg), and in the third experiment, we administered the 5-HT(4) antagonist RS 39604 (0.01, 0.1, 1.0 mg/kg) and 5-HT(4) agonist RS 67333 (0.01, 0.1 and 0.5 mg/kg). The administration of 5-HT(2/3/4) subtype antagonists all generated behavioral profiles indicative of anxiolytic-like effects in the EZM, which was apparent from examination of both traditional and ethological measures. While little effect was observed from 5-HT(2) and 5-HT(3) agonists, the 5-HT(4) agonist RS 67333 was found to produce a paradoxical anxiolytic-like effect similar to that produced by the 5-HT(4) antagonist RS 39604. We conclude by discussing the implications of these findings

Papel da luminosidade do biotério no comportamento do rato no labirinto em cruz elevado Role of vivarium illumination in rat behavior in the elevated plus-maze

Há pouca informação sobre o efeito dos ambientes onde os ratos são mantidos antes de testes. Para investigar o efeito da iluminação do biotério, ratos Wistar machos foram submetidos a um período de 96 h de iluminação contínua, escuridão contínua ou um ciclo claro escuro de 12:12 h e testados no labirinto em cruz elevado em uma sala iluminada (150 lux) ou escura (0 lux). Os resultados mostram que nem a iluminação contínua nem a escuridão contínua do biotério afetam o comportamento dos ratos, quando comparados aos sujeitos mantidos no ciclo claro-escuro de 12 h. A condição de luminosidade durante o teste, no entanto, foi importante: independentemente da condição de iluminação do biotério, os animais testados no escuro exploraram mais os braços abertos do labirinto, um resultado já relatado na literatura e interpretado como diminuição da ansiedade nesse aparato.<br>There is little information about the environments where rats are kept before being tested. In order to investigate the role of vivarium illumination, male Wistar rats were submitted to a 96-h period of continuous illumination, continuous dark or a 12:12 h light/dark cycle and tested in the elevated plus-maze in a lit (150 lux) or a dark room (0 lux). Results showed that neither vivarium illumination nor darkness for 96 h altered the rats' behavior in comparison to that of rats kept under the 12-h light/dark cycle. Luminosity during the test, however, was important: no matter what the vivarium illumination was, rats tested in the dark room explored more the open arms of the maze, an already reported result which is interpreted as decreased anxiety in this apparatus