Effects of 7-OH-DPAT and U 99194 on the behavioral response to hot plate test, in rats.

Aim of present study was to investigate in male Wistar rats, whether behavioral response to hot plate test application could be influenced by systemic administration of 7-OH-DPAT, a dopaminergic (DA) D3 versus D2 receptor agonist, or U 99194, a DA D3 versus D2 receptor antagonist. Each trial lasted no more than 10 s and the whole experimental session lasted 120 min. Animal behavior was recorded by means of a digital videocamera and later, frame by frame examined using a professional videoredorder. Latency of each behavioral pattern, characterizing the response, was analysed, showing significant changes only with U 99194. A multivariate cluster analysis indicated the presence of three main behavioral clusters (exploratory, primary responses to pain, escape) which, also, resulted significantly modified by both drugs. In addition, diagrams of preferential direction, obtained through multivariate stochastic analysis, evidenced switching probabilities differences among different patterns and clusters. Results demonstrate that the behavioral response to hot plate test application is altered following 7-OH-DPAT or U 99194 administration. These findings are discussed in terms of a) drugs influence on behavioral switching and learning processes; b) a likely activity on DA D3 versus D2 receptors.