Physiology & Behavior, Vol. 21, pp. 775--776. Pergamon Press and Brain Research Publ., 1978. Printed in the U.S.A. Up-hill Avoidance: A New Passive-Avoidance Task URSULA STAUBLI AND JOSEPH P. HUSTON Institute of Psychology, University of Diisseldorf, Lab. Comp. and Physiol. Psychology Universitiitsstr. 1, Diisseldorf, West-Germany and Institute of Pharmacology, University of Ziirich, Ziirich, Switzerland (Received 12 May 1978) STAUBLI, U. AND J. P. HUSTON. Up-hill avoidance: A new passive-avoidance task. PHYSIOL. BEHAV. 22(4) 775-776, 1979.--Rodents and many other animal species orient and locomote up-hill when placed on a tilted surface. When placed with head facing downwards on an incline, rats turn around and climb up reliably within a few seconds. This behavior can be suppressed by a contingent tail-shock, and therefore is a suitable response for studying passive avoidance learning. The present report summarizes the effectiveness of various combinations of angle of incline and levels of tail-shock intensity on up-hill avoidance learning in rats. Passive-avoidance Learning Electric shock Geotaxis Rats MANY animal species exhibit a negative geotaxis, i.e. the tendency to orient and locomote toward the top when placed on a slanted surface. When placed on a tilted platform with head facing down-hill, rats and mice invariably turn around and Iocomote up the incline reliably and with a short latency. This behavior, therefore, provides a potentially useful re- sponse for the study of passive avoidance learning. Passive avoidance learning involves learning to avoid noxious stimu- lation by non-performance of a high-probability response. The response should occur reliably with a short-latency, and be easily quantifiable. The present study was undertaken to determine whether the negative geotaxis would be a suitable response to study passive avoidance learning. For this pur- pose various combinations of tail-shock intensity and angles of tilt were examined. METHOD Animals and Apparatus Animals were 48 male albino rats of the Sprague-Dawley strain. They weighed 280-320 g and were maintained in pairs under standard conditions. The experimental apparatus was a 50x50 cm box with 35 cm high gray plastic walls. The box could be inclined at a variable angle (see Fig. 1). The floor consisted of 10 mm dia. stainless steel grid bars placed 13 mm apart. To deliver a tail-shock, a tail-electrode was constructed, consisting of a wire clip (see Fig. 1) connected to a constant current shock source. The room was illuminated with dim fluorescent light- ing. Procedure The animal was first fitted with the tail-electrode and then placed onto the grid with its nose facing the bottom. In order to have the animal calm and inert during the critical moment of being released onto the grid, the rat was swung back and forth three times with wide arm movements of the experi- menter. During baseline-trials the animal's latency to make a 180° turn and initiate the first climbing response was measured. Thereafter the animal was returned to its home cage. During the experimental trials the same latency was measured and additionally a tail-shock was administered contingent on the first climbing response after the 180° turn. Immediately after the shock the animal was placed into its home cage. Retest was measured 24 hr later. An animal was considered to have learned to inhibit the climbing response if it remained with its nose facing the bottom for 180 sec. An experiment was designed to investigate step-up avoidance learning under two conditions of degree of slope (20° and 30°) of the grid floor, comparing two intensities of tail-shock (1.5 and 2.0 mA). A total of 48 animals were assigned to 6 groups, including one control and two experimental groups run with the grid floor tilted at a 20° angle, and one control and two experi- mental groups tested with the angle set at 30° . The two exper- imental groups in each case received either 1.5 or 2.0 mA tail-shock. The control groups did not receive tail-shock, but were otherwise handled exactly as the experimental animals. 1Supported in part by Swiss National Science Foundation Grant No. 3.2270.77. ZReprints obtainable from J. P. Huston at Dtisseldorf address above. Copyright © 1979 Brain Research Publications Inc.--0031-9384/79AM0775-02502.00/0