Psychopharmacology(1991) 104:515-521 0033315891001558 Psychopharmacology © Springer-Verlag 1991 Haloperidol and nucleus accumbens dopamine depletion suppress lever pressing for food but increase free food consumption in a novel food choice procedure J.D. Salamone, R.E. Steinpreis, L.D. McCullough, P. Smith, D. Grebel, and K. Mahan Department of Psychology,Universityof Connecticut, Storrs, CT 06269-1020, USA Received July 1, 1990 / Final version January 22, 1991 Abstract. An important aspect of motivated behavior is that organisms will perform complex instrumental be- haviors to gain access to stimuli such as food. In the present study, food-deprived rats were tested in an op- erant chamber in which the animals had a choice between pressing a lever to obtain a more-preferred food (Bioserve pellets), or free feeding on a less-preferred food (lab chow). Typically, rats pressed the lever to obtain the preferred food pellets, and ate little of the less-preferred food even though it was freely available. Pre-fed rats showed suppression of both lever pressing and feeding. Systemic administration of 0.1 mg/kg hatoperidol (HP) led to a dramatic shift in the behavior of these rats, such that the number of lever presses was substantially re- duced, but the amount of less-preferred food consumed showed a significant increase. This result occurred if the rats pressed a lever on either a CRF or FR5 schedule. Injection of 3.5-7.0 gg HP directly into the nucleus ac- cumbens, or intra-accumbens injections of 6-hydroxy- dopamine, also decreased lever presssing for food and increased feeding on laboratory chow. Thus, interference with brain dopamine suppressed a highly active instru- mental response for food, although the behavior of the animal was still directed towards food acquisition and consumption. Key words: Dopamine Nucleus accumbens Motiva- tion Motor function - Operant - Foraging Interference with brain dopamine (DA) has been shown to suppress a wide variety of behaviors. Administration of DA antagonists decreases the frequency of "spon- taneous" activities as well as appetitive and aversively motivated behaviors (Janssen et al. 1965; Rolls et al. 1974; Fibiger et al. 1976). Depletion of DA from striat- um results in severe motor and sensorimotor dysfun- ctions (Ungerstedt 1971; Marshall et al. 1974; Stricker Off'print requests to: J.D. Salamone and Zigmond 1976). Nucleus accumbens DA depletion has been shown to reduce spontaneous and ampheta- mine-induced locomotor activity (Kelly et al. 1975; Koob et al. 1978). Because appetitive instrumental beha- viors are suppressed potently by DA antagonists, it has been hypothesized that these drugs reduce the "reward- ing impact" of stimuli such as food, water and electrical brain stimulation (Wise 1982; Wise et al. 1978a, b). Early evidence in favor of this view came from studies showing that DA antagonists cause operant responding to decline over time in a way that is similar to extinction on some schedules of reinforcement (Wise et at. 1978a, b). The question of whether or not interference with DA systems blunts the rewarding impact of reinforcers has remained a controversial one (Tombaugh et al. 1980, 1983; Wise 1981, 1985; Stellar et al. 1983; Salamone 1987; Berridge et al. 1989; Horvitz and Ettenberg 1989). DA antagonism and extinction do not produce similar effects across a broad range of conditions (Mason et al. 1980; Tombaugh et al. 1980; Faustman and Fowler 1981, 1982; Evenden and Robbins 1983; Asin and Fi- biger 1984; Salamone 1986, 1987, 1988; Willner et al. 1988). Wise has more recently emphasized the involve- ment of brain DA in incentive-motivation processes (e.g. Wise 1985, 1988). Considerable evidence indicates that brain DA, par- ticularly in nucleus accumbens and striatum, is involved in aspects of motivation (see reviews by Iversen 1977; Mogenson et al. 1980; Robbins and Everitt 1982; Benin- ger 1983; Salamone 1987, 1988, 1991). Release and meta- bolism of DA in nucleus accumbens or striatum is in- creased during lever pressing for food, and during food- induced motor activity (Church et al. 1987; Salamone et al. 1989; McCullough et al. 1990). However, it is clear that interference with DA transmission does not alter all aspects of motivated behavior in a uniform manner. Moderate doses of DA antagonists that markedly sup- press instrumental responses for food, such as lever pressing, do not suppress food consumption (Rolls et al. 1974; Fibiger et al. 1976) or simple approach responses (Salamone 1986). A dose of pimozide that suppressed