Stimulant action of d-amphetamine in relation to test compartment dimensions and behavioral measure

Effects of graded doses of d-amphetamine on avoidance lever pressing were measured for three groups of rats tested in either a “long”, “medium” or “short” compartment. The increase in avoidance rate was significantly less in the long compartment than in the medium or short compartments and the shape of the dose-response curve was different. In the long compartment, in addition, drug effects on general activity, as defined by the rate of breaking a photoelectric cell beam, were measured concurrently with avoidance lever pressing. The minimum dose that increased beam break rate was lower than the minimum dose that increased avoidance rate. The proportional increase in rate with increasing dose was greater for beam breaks than for lever presses. These drug-behavior-apparatus relationships were analyzed in terms of the differential interference by drug-enhanced general activity on lever pressing rates in the three different-sized compartments.