Injection Controls for Drug Studies

Abstract

A BASIC procedure in behavioural pharmacology is the establishment of a dose-effect curve which describes the relation between drug dosage and performance in a certain set of maintaining conditions. Typically, a few animals are trained to work on a particular reinforcement schedule until performance is stable from day to day. Each subject serves as his own control and receives each dose two or three times, one experimental session being devoted to each administration of each dose level. Drug sessions are usually separated by 4–6 days. At least one control session, during which no drug is administered, is run between drug sessions to allow assessment of possible changes in the base-line performance and to provide a further point on the dose-effect curve. A speedier technique is that of cumulative dosing¹. Successive presentations of increasingly larger doses are made at fixed intervals throughout a single long session, and performance during this session is compared with performance during a similar session in which the drug is not administered. Inasmuch as these techniques are concerned with a comparison between on drug and drug administration, then the non-pharmacological differences between drug and control procedures are interesting, to our knowledge, control procedures for injection have not been investigated, and a worried novice finds little advice on the matter in standard texts^1,2. During the establishment of a dose-effect curve relating chloropromazine dosage and the performance of rats working on a schedule of reinforcement which prescribed food delivery for every fifth lever press (FR5), we employed different control procedures at different stages of the study and found variations in baseline performance which seemed to be related to the differences in control procedure.