Resumo

Objective: The objective of the present study was to evaluate the effect of the NMDA-lesion in the ventrolateral striatum of rats on predatory hunting. Methods: Adult male Wistar rats (n = 26), weighing 280-320 g and adult cockroaches (Picnocellus surinamensis) were used in this experiment. Food and water were supplied ad libitum, except one day before each hunting session, when the rats were left to fast for 24 hours. The hunting sessions were carried out in the morning. In each session the rat was placed inside a wood box (47 x 24 x 22 cm) with a front glass panel through which the experiment was video-recorded. After the animals were left to habituate in the box for 1 h, five cockroaches were introduced inside the box and the following parameters were scored: latency to start hunting, number of successful captures, number of capture attempts, time spent eating, time spent displaying other behaviors than hunting (e.g., grooming, general exploratory activity and resting), and the total hunting time. Following the first session, the rats were divided in three groups: control rats (9); sham-lesioned (9); and NMDA-lesioned rats (8). The rats of the sham and NMDA groups were submitted to a stereotaxic surgery in which 20 mg NMDA (in 1 µL) or the same volume of saline was infused bilaterally into the ventrolateral striatum. After the rats recovered from the surgery for one week their hunting behavior was scored in the same manner as described above. Data were analysed by two-way ANOVA followed by the Newman Keuls test and differences were considered significant when p < 0.05. Results: Compared to the control groups, the following significant alterations were observed in the hunting behavior of the NMDA-lesioned rats: higher latency to start hunting (F2,23 = 3.30, p < 0.05); increased time spent in the predatory activity (F2,23 = 6.48, p < 0.01); increased time eating the roaches (F2,23 = 10.39, p < 0.01); a reduced ratio number of attempts to capture the roaches/number of successful captures (a score of the efficiency of hunting) (F2,23 = 10.13, p < 0.001). Conclusion: The present results suggest that normal predatory hunting behavior of rats depends on the integrity of the ventrolateral striatum.