SENSATION SEEKING 2

Sensation seeking has been studied as a potential characteristic for addiction-prone individuals. In these experiments, we trained rats to make nose-pokes into an “active hole ” that produced a flashing light and tone or an “inactive hole ” that produced nothing. During testing sessions, we compared the responses of amphetamine-treated rats to responses of vehicle-treated rats. We hypothesized that the stimulus would be inherently rewarding and that amphetamine would increase this effect. Our results showed that, rats did not make more active than inactive nose-pokes after vehicle injection, while amphetamine-treated rats made many more active hole nose-pokes. We also found that the increase in sensation-seeking induced by amphetamine only occurred when rats were given amphetamine on the first day of testing, when the stimuli were more novel. In addition, we measured neural activity within the ventral pallidum, a brain area involved in the processing of rewards and reward-related stimuli. During testing sessions, we recorded ventral pallidal neural activity and assessed whether amphetamine-induced increases in dopamine alter neuronal firing within the ventral pallidum in response to novel stimuli. We found that more ventral pallidal neurons were responsive to the active than inactive nose-poke hole and that amphetamine caused an increase in responsive units. These results indicate that novel stimuli may be processed similarly to food and drugs in the ventral pallidum