Bait-shyness acquisition and resistance to extinction as functions of US exposure prior to conditioning

Abstract

Cyclophosphamide-induced aversions to saccharin-flavored tap water were observed in normal control rats, in rats subjected to varying numbers of cyclophosphamide injections prior to conditioning, and in rats similarly subjected to preconditioning saline injections. Both initial magnitude and resistance to extinction of a conditioned flavor aversion were found to be inverse functions of preconditioning familiarity with drug-induced illness. Six preconditioning cyclophosphamide injections markedly reduced both initial aversion magnitude and resistance to extinction. In contrast, three such injections fail ed to affect initial aversion magnitude and resulted in a small acceleration of extinction rate, while one preconditioning cyclophosphamide injection produced no observable effects. These findings depict preconditioning familiarity with illness as one important variable modulating the strength of conditioned flavor aversions and emphasize the importance of viewing resistance to extinction as one indicator of aversion strength.Bait-shyness, the learned avoid ance of a substance whose consum ption is followed by a case of nonlethal poisoning, is conveniently studied in laboratory rats by following the ingestion of a palat abl e flavor with illness induced by to xic injection or ex posure to ionizing radiation (cf, Garcia & Koelling , 1967 ; Revusky & Gar cia, 1970). Flavor familiarity prior to condit ioning is one important variable influencing the strength of these conditioned aversions. Numerous studies have shown th at preconditioning flavo r fam iliarity reduces th e strength of both radiati on and drug -induced flavor aversions (Ahlers & Best , 1971 ;Domjan , 1972 ;Elkins, 1973a; Farley, McLaurin , Scarborough, & Rawlings , 1964; Revu sky & Bedarf, 1967;Vogel & Clody, 1972; Wittlin & Brookshire, 1968). A related problem , which has received less attention , involves famili arity with illness prior to conditioning. Brookshire and Brackbill (1971) reported that 10 pre conditioning injections of apomorphine hydrochloride blocked the development of an apomorphine-induced flavor aversion . Apomorphine hydrochloride induces nausea and vomiting in humans and has been used in aversion therapy for alcoholism. However, Lemere and Voegtlin (1950), who t reated over 4,000 alcoholics with " conditioned reflex therapy," a procedure based on repeated pairings of alcohol ingestion with chemically induced illness , advised against apomorphine as a conditioning agent because their results suggested its effectiveness was to som e extent negated by its sedative action. Similarly, the aversion attenuation reported by Brookshire and Brackbill (1971 ) might be, in part , a funct ion of narc otic effects as *A preliminary revision of this paper was presented at the 1972 meeting of the Southwestern Psychological Association, Oklahoma City. MeadJohnson Laboratories) is, th erefore, indicated. Since functional relationships between bait-shyness and differing amounts of preconditioning toxic illnesses are unknown, this experiment al...

Habituation to illness: Effects of prior experience with the US on the formation of learned taste aversions in rats

“…Further, habituation may not only reduce unconditioned suppression to a stimulus, but rnay also block conditioning to it in a manner similar to preexposure to the CS (Lubow, 1965). Results of Experiment 1, in which a conditioned aversion to saccharin was blocked by three preconditioning LiCl intubations, support similar results by Brookshire and Brackbill (Note 1) and Elkins (1974). In both of these studies, an inverse relation was found between the frequency of the preconditioning exposure to toxie illness and the initial magnitude of the aversion.…”

“…An interesting difference between the results of the present study and that of Elkins (1974) concerns the degree of attenuation of the learned association following preconditioning habituation to the USo Elkins reported that, following six preconditioning cyclophosphamide injections, a learned aversion to saccharin was formed whieh lasted at least 10 days before extinguishing, while the present study revealed no aversion to saccharin following only five preconditioning LiCI intubations. It is probable that these conflicting results are due to differences in the toxins used.…”

“…Although Elkins (1974) and Brookshire and Brackbill (Note I) attempted to account for their data, their results do not clarify the mechanism by whieh preconditioning US exposure weakens subsequent aversions. Results of Experiment 2 indicate that habituation to illness may be a contributing factor, since less attenuation of activity was found on successive poisonings, just as the magnitude of the conditioned aversion to saccharin varied over successive poisonings in Experiment 2.…”

“…Philadelphia. Pennsylvania 19122. chloride as the US, and by Elkins (1974), using cyclophosphamide. Brookshire and Brackbill were further able to show that exposure to the US prior to conditioning can alter the effectiveness of the US at the time of the CS-US pairing, but that exposure after conditioning cannot.…”

The effect of drug habituation before and after taste aversion learning in rats

“…Kremer (1971), Rescorla (1973), andSiegel and Domjan (1971) found that habituation to shock or loud noise attenuated the ability of a stimulus subsequently paired with the shock or noise to suppress barpressing for food. In the experiments of Brackbill (1971, 1976), Cannon, Berman, Baker, and Atkinson (1975), Elkins (1974), and LeBlanc and Cappell (1974), habituation to apomorphine, ethanol, lithium chloride (LiCl), cyclophosphamide, morphine, or amphetamine reduced the subsequent efficacy of these drugs in reinforcing aversions to saccharin.Habituation to the reinforcer after learning, however, mayor may not reduce the conditioned responses shown in a subsequent test. When Rescorla (1973) habituated rats to a loud noise after pairing the noise with a light, the habituation hastened later extinction of conditioned suppression in the light.…”