Abstract
A dose of d-amphetamine which completely suppressed all responding was administered to each of five pigeons under an FR 30 schedule. When the pigeons were treated with chlorpromazine after 45 min or more, responding was restored. When d-amphetamine and chlorpromazine were administered simultaneously to three other pigeons, responding was better maintained than after d-amphetamine alone. This study confirms a previous finding that chlorpromazine can antagonize the rate-decreasing effect of d-amphetamine.