Ethanol as a positive reinforcer via the oral route for rhesus monkeys: maintenance of fixed-ratio responding.

Two rhesus monkeys were required to emit 1 to 16 responses (FR 1, 2, 4, 8, and 16) per 0.5 ml delivery of either 8% (w/v( ethanol or water. Ethanol had been established as an effective reinforcer via the oral route in an earlier experiment [4]. At FR 16, responding maintained by ethanol clearly exceeded responding maintained by water for both monkeys. The volume of ethanol intake per session remained nearly constant from FR 1 to FR 16, however, the volume of water consumed per session decreased when FR 16 was required.