PM285. Neuropharmacological effect of ketamine-induced hyperlocomotion modulated by age in the C57BL/6J mice

Background: Ketamine, an antagonist on N-methyl-D-aspartate (NMDA) receptor, can produce neurobehavioral changes ranging from mood alterations and psychotic episodes in human to hyperactivity and stereotyped motion in mice. In the study, we tested the pharmacological properties of ketamine on anxiety, locomotion and motor activity.

Materials and Methods: Subjects were C57BL/6J mice with age of 6 and 12 weeks at the time of testing. Mice were housed in a temperatureand humidity-controlled vivarium under a 12 h life-dark cycle with ad libitum access to food and water. Sensitivity to acute intoxicating effect was assessed using accelerating rotarod under given doses of ketamine (0, 10, 25, 50 mg/ kg, respectively). The elevated plus-mage (EPM) was used to evaluate the anxiety-like behaviors. Open field with videotracking system was adapted to measure the motor responses following acute and chronic ketamine injections.

Results: The results demonstrated that the ketamine could dose-dependently potentiate the motor ataxia and significantly increased the open-arm entries at the dose of 25 mg/kg through EPM assessment. Ketamine produced hyperactivity at the age of both 6 and 12 weeks. The adolescent mice significantly increased the total moving distance and speed compared to the adult group.

Conclusion: These findings suggest that the effect ketamine is regulated by age and potentiating the sensitivity in the adolescent mice. PM286 Cocaine modifies preference of choice in rat gambling task Bo Ram Cho, Wha Young Kim, Myung Ji Kwak, Jeong-Hoon Kim Department of Physiology, Brain Korea 21 Plus Project for Medical Science, Yonsei University College of Medicine, Seoul 03722, Korea Abstract Background and

Aims: Rat gambling task (rGT) is one of the most sophisticated animal model which shares many of the features of the human gambling tasks including uncertainty, reward and punishment. In this model, how cocaine affects the preference of choice has been examined.

Methods: Rats were trained in a touch screen chamber to learn the relationships between 4 different light signals on the screen and accompanied reward outcomes and punishments set up with different schedules, for one session of 30 min each day. Then, they were allowed for free choices out of 4 different light signals. Once animals showed a stabilized pattern of preference, they were given 7 days of either saline or cocaine IP injections (a single injection per day) followed by 2 weeks of withdrawal. Then, their preference of choice was re-tested in rGT chambers.

Results: Depending upon their preference of choice, rats were separated as either risk-averse or risk-seeking groups. However, when they were exposed to cocaine, rats in the risk-averse group significantly changed their preference toward more disadvantageous choices.

Conclusions: These results indicate that cocaine influences even different types of decision-making behavior as in gambling task, which is not directly relevant with obtaining cocaine itself, implying that they may aggravate pathological symptoms of bad choices, resulting in negative consequences, observed in the patients with behavioral addictions.