PHARMACOLOGICAL VARIABLES 
DOSE-EFFECT RELATIONSHIPS 
A hallmark of behavioral pharmacology research is the determination of dose-effect 
relationships. That is, a range of doses is selected that encompasses one producing no or very 
little effect up to one at which the animals do not perform the target response. Dose-effect 
relationships may be determined by studying single doses in separate groups of animals 
(between-subject designs) or by determining a full dose-effect relationship in each animal 
(within-subject, or repeated-treatments designs). The baseline performance usually is 
reestablished between sessions in which a drug is given. 
Drug doses given by the experimenter can be given acutely (e.g., a single injection of a drug 
before a session once or twice a week) or chronically (e.g., once or more daily for some length 
of time), but there is a range of variations. In drug interaction studies, two doses, each of a 
different drug, would be given at appropriate temporal intervals before the behavioral test. 
Cumulative dosing procedures may be used. In these, increasing doses of a drug are 
administered within a relatively short period, and a brief experimental session is conducted 
after each dose. The effects of the drug are assumed to cumulate in an additive manner so 
that within a period of two to three hours the effects of a range of doses can be determined 
(Wenger, 1980). 
Drug self-administration experiments determine the drug’s reinforcing efficacy, which may 
indicate the drug’s potential for abuse. The animal controls the number and frequency of 
delivery of the test drug. That is, a quantity of a particular drug is available intravenously, 
orally, or via inhalation, and the subject of interest is the amount of behavior maintained by 
this drug at the self-administered dose. In such studies, the dose available is varied across 
experimental conditions, and the rate of responding to obtain the dose, the number of drug 
deliveries obtained, and/or the amount of drug taken are the primary dependent variables of 
interest. In such studies, the likelihood that the animal will produce a fatal overdose is 
carefully considered in the design and choice of drug. Drugs vary across classes in how likely 
it is that high drug doses will produce adverse effects. Overdose may be minimized by placing 
an upper limit on the number of doses per session or on the minimum time-lapse between 
doses, or by setting the magnitude of each dose available to the animal. 
DRUG VEHICLES 
Most drugs are provided to researchers in solid form and must be dissolved or suspended in a 
liquid carrier (vehicle) in order to be administered. Aqueous vehicles (e.g., sterile water, 
saline) have no pharmacological action of their own; however, many drugs need more 
complex vehicles (e.g., one that has an organic solvent, such as propylene glycol, or an 
alcohol). Testing with the vehicle, without a drug, will provide a control for the vehicle’s 
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