Amobarbital Sodium and the Effects of Reward and Nonreward in the Amsel Double Runway

Abstract

Rats received 60 trials (Condition I) with 6 pellets reward at the second goal of a double runway and either 6 ( n = 12) or 0 ( n = 12) at the first goal, followed by, for all Ss, 24 trials (Condition II) with 0 reward at the first goal, then 36 trials (Condition III) with 50% reward at the first goal. Half of each reward group received amobarbital sodium (20 mg/kg, IP) and half saline prior to the 6 daily trials. Neither excitatory nor inhibitory effects of the reward shift occurred in Condition II. In Condition III inhibitory effects were observed to occur anticipatory to the first goal; these were reduced in magnitude by the drug. Excitatory effects of nonreward occurred after the goal if this effect is defined as increased speed relative to that in Condition II or greater speed on nonreward trials relative to reward trials in Condition III. These differences were not reduced by the drug. Problems concerning the possible “demotivating” effects of reward were raised which are not yet completely resolved.