LACK OF INSTRUMENTAL CONDITIONING WITH INTRAGASTRIC REINFORCEMENT IN NORMAL EXPERIMENTAL PROCEDURE

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1 ACTA NEUROBOL. EXP. 1972, 32: LACK OF NSTRUMENTAL CONDTONNG WTH NTRAGASTRC RENFORCEMENT N NORMAL EXPERMENTAL PROCEDURE Jerzy CYTAWA, Danuta LUSZAWSKA, Ryszard SCHOENBORN and Marian ZAJqC Department of Animal Physiology, Curie-Sklodowska University Lublin, Poland Abstract. The subject of this study was to check whether it would be possible to establish the alimentary instrumental reflex with direct intragastric reinforcement in normal experimental procedure. The experiment was carried out on ten male albino rats. Seven animals which were permanently implanted with intragastric tube constituted the experimental group. The remaining three rats served as controls. On the basis of obtained results we conclude the following: (i) in normal experimental procedure of conditioning it s impossible to establish a conditioned instrumental response with intragastric reinforcements, at least when the reinforcement amount is 0.5 ml; (ii) instrumental responses with intragastric reinforcement can be obtained using the method of transfer from reflexes with oral reinforcement. NTRODUCTON Since the time when Konorski and Miller (6) started their studies on conditioned reflexes type 11, many experiments have been carried out and many facts gathered, particularly those concerning the mechanism of formation of instrumental conditioned reflexes with food fieinforcement. The experimental data obtained from those experiments made it possible to formulate general conceptions elucidating the mechanism of instrumental alimentary conditioned reflexes. According to Konorski's theory (7), based on reinforcing action of the hunger antidrive, the alimentary instrumental reflexes constitute in fact preparatory responses controlled by the hunger drive, aiming to provide the appropriate alimentary stimuli. Those stimuli activate the antidrive that inhibits the hunger drive while they elicit the consummatory alimentary reflex.

2 768 J. CYTAWA ET AL. The large majority of experiments on alimentary instrumental reflexes were oarried out with the use of procedures in which the instrumental reaction of an animal in response to the conditioned stimulus was reinforced by food taken orally. t is known that the role of taste stimuli in the process of formation of alimentary instrumental reflex is great. As it was shown by one of the authors of this paper (1-3), the reinforcement of instrumental reflexes with a very small amount of food, insufficient to produce satiation of the animal, is enough for the reflex to establish and to show even a big stability and resistance to the phenomenon of fatigue of conditioned reflex due to frequent repetition of the conditioned stimulus. nstrumental reflexes with direct intragastric reinforcement are a kind of curiosity because they lack activation of hunger antidrive by taste and smell of f d and they also lack a proper consummatory reaction. n the light of the theory of formation of instrumental conditioned reflex the possibility of obtaining reflexes by direct intragastric reinforcement, i.e., omitting oropharyngeal stimuli, which signal the presence of food in the mouth and elicit consummatory reflexes, is quite obscure. Successful instrumental conditioning with intragastric reinforcement, described by Epstein (4), Epstein and Teitelbaum (5), Teitelbaum and Epstein (10) and Snowdon (9), actually appeared to be the result of transfer of the instrumental reflex with oral reinforcement into the reflex with intragastric reinforcement. n some cases, as it was shown by McGinty, Epstein and Teitelbaum (8), the introduction of oral incentive with saccharine solution to each reaction simultaneously with intragastric reinforcement was indispensable to maintain responding. From the standpoint of the theory of alimentary instrumental conditioned reflexes it can be assumed that the alimentary instrumental reflex with intragastric reinforcement should not be established at all when a normal experimental procedure is applied. To check this assumption the present studies were carried out. MATERAL AND METHOD The experiments were carried out on the male albino rats of the Wistar strain, at the weight of g at the beginning of experiment. Seven out of the animals were permanently implanted with the intragastric tube under general anesthesia with 5Oo hexobarbitd natrium, according to the operation procedure described by Zajqc (11). That tube allowed the liquid food to be infused directly into the stomach of the animal and at the same time a rat could easily take food through the mouth. After 1 week's reconvalescence the proper experiments were started. Animals, previously starved for 24 hr, were placed in the apparatus for investigation of instrumental reflexes with direct intragastric

3 reinforcement, described in details by Zajqc (11). They were examined for 6 hr every day during 15 successive days. During a 6-hr experimental session the animals had access to a bar which being pressed brought about infusion of 0.5 rnl of liquid food heated up in the body's temperature in a water bath. The reactions performed during the food infusion, i.e., during 5 sec operation of a pumping device, were not reinforced. A liquid diet of the following composition was used: 1. condensed milk ml 2. egg (one whole egg) - 50 rnl 3. sugar - 24 g 4. distilled water - 24 ml 5. natriurn chloride g /o formalin ml 7. multiple vitamine preparation ml During the first 5 days of the experiment a procedure was applied in which each reaction of the rat, i.e., pressing the bar, caused infusion of 0.5 ml of liquid food directly into its stomach. n this period of experiment the investigation was carried out whether the reflex would establish spontaneously with the normal experimental procedure. During the following 5 days the experimental conditons were changed so that the rat, after accomplishing the instrumental response, received reinforcement of the same amount but into the cup placed opposite the bar. n the last 5-day period of the experiment the tube infusing food was again connected with the gastric tube so that each pressing upon the bar resulted in infusion of of liquid food directly into the stomach. n all three experimental stages the animals kept outside the experimental apparatus did not receive food but only water. To determine the number of accidental responses of bar-pressing performed by the animals kept in the experimental apparatus, three rats without implanted intragastric tube, after 24 hr of starvation, were placed for 6 hs every day during 5 suocessive days in the apparatus for investigation of instrumental responses. Those rats had also access to the bar but no portion of fwd was released when they pressed it. To preserve control experimental conditions, the animals did not receive food during the whole time of experiment. RESULTS The results of the whole experiment are presented in Fig. 1. During the first 5 days the number of instrumental responses of bar-pressing, reinforced with food given directly into the stomach was very small and 2 - Acta Neurobiologiae Experimentalis

4 770 J. CYTAWA ET AL. its median and mean quadrilla deviation values ranged from 4.0 $- 3.5 to 6.0 k 5.0. During the following 5 days, when instrumental responses were reinforced by food given in the cup, the number of responses rapidly increased. On the first day following the transfer of the animals to oral reinforcement, that number was 35.0 _ During the next 4 days it ranged from 48.0 f 15.5 to 65.0 $ V3 60 W V) Z 0, " o W CT 20 0 r. M,,, Fig. 1. Acquisition of instrumental conditioning with intragastric or oral reinforcement. Responses of sevent rats are given in median f mean quadrilla deviation. Additional explanation in the text. ' When the animals returned to intragastric reinforcement in the period between the 11th and 15th day of the experiment, instrumental responses were continued and their performance decreased only slightly in comparison to the preceding period and ranged from to 53.0 f The median values of the number of responses performed by control animals ranged from 3.0 $- 2.0 to 9.0 k 1.5, i.e., at the same level as in the first experimental stage i 'l.ll" 13 " 15 DAYS NTRAGASTRC 5 1 ORAL NTRAGASTRC N DSCUSSON The results of the experiments carried out seem to indicate the impossibility of direct formation of the instrumental reflex with intragastric reinforcement, at least with the use of applied quantity of reinforcement, i.e., 0.5 ml of liquid food heated to body temperature and infused into the stomach within 5 sec. The few reactions of pressing the bar

performed in the first experimental stage should be considered as accidental ones. Although they were reinforced by intragastric infusion of food, no instrumental response was elicited.

5 performed in the first experimental stage should be considered as accidental ones. Although they were reinforced by intragastric infusion of food, no instrumental response was elicited. The number of instrumental responses performed in that time did not exceed the values obtained with the control animals, and they undoubtedly resulted from exploratory activity of the animals and from increased motor activity caused by heightened hunger drive. Searching for the factor producing the decrease of hunger drive in the procedure of establishing the instrumental response with intragastric reinforcement, abtention should be drawn to such a factor that would occur in a relatively short time after accomplishing the instrumental response and that the animal could associate it with the performed movement. Among the factors appearing after the direct intragastric infusion of food, loading the stomach seems to fulfill those conditions. However, the 0.5 ml amount of reinf~rcem~ent used in this experiment, being several times smaller than the average size of the usual meal of a rat, which is about 3 ml (9), and infused into the stomach during 5 sec probably was too weak as a stimulus. Besides it could not be detected and associated with the performed movement, because the temperature of food was the same as that of the animal's body. Almost an instant formation of the instrumental response with oral reinforcement proves the role of the smell and taste receptors to be potent in the mechanism of establishing of alimentary instrumental reflexes. The reason for which the instrumental responding continued after the animals were transferred from oral to intragastric reinforcement should also be given consideration. The behavior of the animal in that stage of experiment was similar to that usually observed during extinction of instrumental responding. Lack of f d in the cup after accomplishing the instrumental response resulted in the rats' return to performing the trained movement at a high frequency and rapidity. A great number of responses performed in a relatively short time lead to infusion of a big amount of food, considerably loading the stomach which, being detectable by the mechanoreceptors, could satisfy hunger and stop the performance of instrumental responses. t is interesting that in this time the animals demonstrated, besides their return to the cup after the instrumental response was accomplished, a reflex of snout washing after a series of responses analogically to that observed after finishing the meal in the time of oral reinforcement. Such a behavior was not observed in the first experimental stage when small portions of food were infused into the stomach as a result of accidental bar-pressing. Moreover, after transferring the animals from oral to intragastric

772 J. CYTAWA ET AL. reinforcement, a slight decrease of the number of performed instrumental responses was observed land in consequence a diminution of the taken amount of food.

6 772 J. CYTAWA ET AL. reinforcement, a slight decrease of the number of performed instrumental responses was observed land in consequence a diminution of the taken amount of food. This fact would be in agreement with Snowdon's observations (9), who reported a decrease of the amount of food consumed by in rats fed intmgastrically in relation to animals fed orally. He interpreted this fact as a decrease of alimentary motivation occurring in the case where the receptors of taste and smell were bypassed. This investigation was supported by the Polish Academy of Sciences under Agreement No for researches on "Central regulation of alimentary activity". 1. CYTAWA, J Studies on the fatigue of conditioned reflexes.. Fatigue of the alimentary motor conditioned reflexes. Acta Physiol. Pol. 15 : CYTAWA, J Studies on the fatigue of conditioned reflexes. 11. Fatigability of the alimentary motor conditioned reflexes in relation to the alimentary center excitability. Acta Physiol. Pol. 16 : CYTAWA, J On the phenomenon of exhaustion of conditioned reflexes Dependence of exhaustion on the strength of the conditioning stimuli. Acta Physiol. Pol. 17 : EPSTEN, A. N Water intake without the act of drinking. Science 131 : EPSTEN, A. N. and TETELBAUM, P Regulation of food intake in the absence of taste, smell and other oropharyngeal sensations. J. Comp. Physiol. Psychol. 55 : KONORSK, J. and MLLER, S Podstawy fizjologicznej teorii ruch6w nabytych. Ruchowe odruchy warunkowe. Ksiqinica Atlas, Warszawa. 7. KONORSK, J ntegrative activity of the brain. An interdisciplinary approach. Univ. Chicago Press, Chicago. 531 p. 8. McGNTY, D., EPSTEN, A. N. and TETELBAUM, P The contribution of oropharyngeal sensations to hypothalamic hyperphagia. Anim. Behav. 13 : SNOWDON, C. T Motivation, regulation, and the control of meal parameters with oral and intragastric feeding. J. Comp. Physiol. Psychol. 69 : TETELBAUM, P. and EPSTEN, A. N The role of taste and smell in the regulation of food and water intake. n Y. Zotterman (ed.), Olfaction and taste. Pergamon Press, New York, p ZAJAC, M Technical solution of the problem of investigations of instrumental conditioned reflexes with intragastric reinforcement. Acta Physiol. Pol. (in press). Received 29 January 1972 Jerzy CYTAWA Department of Physiology, School of Medicine Al. Zwyciqtwa 42, Gdafisk- -Wrzeszcz, Poland. Danuta LUSZAWSKA, Ryszard SHOENBORN and Marian ZAJAC, Department of Animal Physiology, Curie-Sklodowska University, Akademicka 19, Lublin, Poland.

Short communication NORADRENERGIC STIMULATION OF THE LATERAL HYPOTHALAMUS AS A REINFORCEMENT IN T MAZE LEARNING IN RATS

ACTA NEUROBIOL. EXP. 1978, 38: ROM13 Short communication NORADRENERGIC STIMULATION OF THE LATERAL HYPOTHALAMUS AS A REINFORCEMENT IN T MAZE LEARNING IN RATS Jerzy CYTAWA and Edyta JURKOWLANIEC Department