Measurement of the lowest dosage of phenobarbital that can produce drug discrimination in rats.

Rationale: Accurate measurement of the threshold dosage of phenobarbital that can produce drug discrimination (DD) may improve our understanding of the mechanisms and properties of such discrimination.

Objectives: This study aimed to compare three methods for determining the threshold dosage for phenobarbital (D) versus no-drug (N) DD.

Materials And Methods: Rats learned a D versus N DD in two-lever operant training chambers.