Psychopharmacology 49, 69-73 (1976) Psycho- pharmacology 9 by Springer-Verlag 1976 Fear-Dependent Variations in Continuous Avoidance Behavior of Pigs I. Lack of Effect of Diazepam on Performance of Discriminative Fear Conditioning R. DANTZER* and P. MORMEDE I.N.R.A., Station de Pharmacologie-Toxicologie, 180 chemin de Tournefeuille, F-31300 Toulouse, France Abstract. Pigs trained to avoid shocks by crossing a barrier in a shuttle-box according to a continuous avoidance procedure were submitted to a Pavlovian discriminative fear-conditioning procedure in which a tone was always followed by unavoidable shock (CS+) and another tone never followed by shock (CS-). The presentation of the CS + on a test session in the shuttle-box induced an increase of the response rate while the CS- decreased the performance. Diazepam (I mg/kg) administered before the test ses- sion did not modify the changes in avoidance response to each CS. Key words." Pig - Continuous avoidance behavior - Discriminative fear conditioning - Diazepam. Pavlovian procedures can affect instrumental behavior (Maier et al., 1969): usually a conditioned fear signal (CS+) is established by pairing a signal with electric shock and then looking for facilitation by CS + of a previously learned avoidance response; however, if a safety signal (CS-) predicting the nonoccurrence of shock is presented it will weaken the avoidance response. If diazepam has anxiolytic properties it should inhibit the facilitation of performance when the CS+ is presented while if diazepam has response- releasing properties it should impair the weakening of performance by the CS-. The present experiments were designed to explore the possibility of affecting continuous avoidance behavior in pigs by means of Pavlovian conditioned signals and to study the effects of diazepam on the changes in performance. In previous experiments with pigs it has been shown that diazepam disinhibits suppressed behavior in a conflict-punishment procedure (Dantzer and Roca, 1974). The usual anti-anxiety interpretation of this effect has been questioned, arguing that diazepam increases food motivation (Wise and Dawson, 1974) and/or has more general disinhibitory effects on sup- pressed behavior (Margules and Stein, 1968). In spite of the fact that diazepam has usually far larger effects on performance than those produced solely by changes in food motivation (Dantzer, in press), the drug- induced eating makes difficult the interpretation of the results in terms of reduced fear or response- releasing properties. In order to explore the effects of diazepam further, conditioning techniques which do not rely on food intake, have to be used. Using avoidance conditioning techniques, several investigators have reported that fear conditioned by * offprint requests should be sent to: Dr. R. Dantzer, INRA, Laboratoire de Pharmacologie, 180 chemin de Tournefeuille, F-31300 Toulouse, France. METHODS Subjects. Eight female and castrated male pigs from crossed breeds were used. They were 7-10 weeks old and weighed 12-17 kg. They usually lived two in each pen. The animal house was illuminat- ed from 7 a.m. until 8 p.m. Water was available ad lib. while food was rationed to about 4 ~ of the body weight. Apparatus. The inside of a ventilated soundproof room was made into a shuttle-box with two compartments, each 133 cm wide x 112 cm long, with a wire mesh floor, and separated by a wooden barrier. A 14 cm barrier was used at the beginning of the learning and was replaced after 2 learning sessions by a 23.5 cm barrier. Each floor was mounted on a pivot located under the barrier: the weight of a pig on the tilting floor depressed a microswitch mounted at the other end of the compartment, indicating the posi- tion of the animal. The electric shock stimulus was provided by an induction coil operated by batteries and having an open circuit output of 5 kV pulses 10 ~ts apart at 100 pulses/s. Shock was applied between the floor and a brass electrode applied to the skin behind the shoulder by means of a leather harness. A conductive electrolyte paste ensured a good contact. A high tone electric bell and a low tone buzzer could be sounded while the pig was working. Pavlovian conditioning was carried out in a 120 x 80 x 75 cm metal metabolism cage, with a wire mesh floor, located in another ventilated soundproof room. Serial resistances were used to control the intensity of the electric shock.