Reinforcing properties of ethanol in neonatal rats: Involvement of the opioid system.

Toward understanding why infant rats ingest high levels of ethanol without initiation procedures, the authors tested effects of mu and kappa receptor antagonists on ethanol reinforcement in neonatal rats. After an intracisternal injection of CTOP (mu antagonist), nor-Binaltorphimine (kappa antagonist), or saline, newborn (3-hr-old) rats were given conditioning pairings of an odor with intraorally infused ethanol or a surrogate nipple with ethanol administered intraperitoneally (to minimize ethanol's gustatory attributes). In each case, these opioid antagonists reduced or eliminated ethanol's reinforcement effect. The same effects occurred with saccharin as the reinforcer in olfactory conditioning. The results imply that activation of mu and kappa receptors, apparently acting jointly, is necessary for reinforcement or that antagonists of this activity impair basic conditioning. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Hunger enhances the expression of calorie- but not taste-mediated conditioned flavor preferences.

Compared ethanol-mediated flavor preferences to preferences mediated by saccharin, which is sweet but noncaloric, and sucrose, which is both sweet and caloric in 4 experiments, using 74 Long-Evans rats. Ss learned to associate grape or orange flavor conditioned stimulus/stimuli (CS) with (1) ethanol or saccharin solution or (2) either the other unconditioned stimulus/stimuli (UCS) or plain tap water. They were then given 2-bottle choice tests between the flavor CSs apart from the UCSs. Flavors associated with 5% ethanol were preferred over saccharin-paired and water-paired flavors by sated Ss, and food deprivation during the choice test enhanced this preference. Flavors associated with 8% sucrose were preferred over water-paired flavors, and this preference was also enhanced by food deprivation. Flavors associated with 0.028% or 0.25% saccharin were preferred over flavors paired with water. In all cases, calorie-mediated preferences, at their highest levels, were stronger than taste-mediated preferences. (20 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Yoked delivery of cocaine is aversive and protects against the motivation for drug in rats.

In Experiment 1, water-deprived rats had 5-min access to saccharin followed by active or yoked intravenous delivery of saline or cocaine (0.33 mg/infusion). Both cocaine groups avoided intake of the saccharin cue following saccharin–cocaine pairings; however, the rats in the yoked condition exhibited greater avoidance of the taste cue than did the actively administering rats. Experiment 2 evaluated subsequent self-administration behavior on fixed- and progressive-ratio schedules of reinforcement. The results showed that prior yoked exposure to cocaine reduced subsequent drug-taking behavior on a progressive-ratio but not on a fixed-ratio schedule. Finally, Experiment 3 used a choice test to determine the impact of yoked drug delivery on the relative preference for cocaine versus water. The results showed that rats with a history of self-administering cocaine preferred to perform operant behaviors on the side of the chamber previously paired with cocaine, whereas the rats with a history of yoked delivery of cocaine avoided this side. These data show that, in most rats, the unpredictable, uncontrollable delivery of cocaine protects against the subsequent motivation for cocaine through an aversive mechanism. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Tegmental pedunculopontine lesions in rats decrease saccharin's rewarding effects but not its memory-improving effect.

The tegmental pedunculopontine nucleus (TPP) of the brainstem has been identified as a critical substrate for both opiate and food reward in nondeprived rats. In this study of rats, TPP lesions blocked saccharin-conditioned place preferences, in both the presence and the absence of water deprivation. TPP lesions also attenuated the unconditioned intake of saccharin and water over several hours after recovery from food and water deprivation. TPP lesions did not block saccharin preferences over water in short-duration tests. The researchers propose that the absence of a lesion effect may reflect previously conditioned discriminations. TPP lesions had no effect on the ability of posttrial presentations of a 3.2% saccharin solution to improve LiCl-conditioned taste aversions. TPP lesions dissociate 2 behavioral processes elicited by saccharin: one mediates unconditioned-reward-conditioned-reinforcing effects, and another mediates the memory-improving effect. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Behavioral analysis of the saccharin deprivation effect in rats.

The deprivation effect (DE)--an increase in the level of free-choice consumption of alcohol after a period of forced abstinence--may reflect relapselike drinking and be relevant for modeling alcohol abuse. However, the behavioral mechanisms of the DE are unclear. In these experiments, rats had unlimited free-choice access to water and saccharin-containing solutions and underwent repeated episodes of saccharin deprivation. It was found that DE magnitude correlates positively with the deprivation phase duration, expression of the DE is highly context dependent, and the DE can be prevented by extinguishing response to the saccharin-associated stimuli. Thus, DE procedures may be useful for studying the effects of continued exposure to stimuli associated with various primary reinforcers such as drugs of abuse. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Corticosterone Increases Depression-Like Behavior, With Some Effects on Predator Odor-Induced Defensive Behavior, in Male and Female Rats.

This experiment examined the effect of repeated corticosterone injections on anxiety and depression-like behavior in male and female rats. Rats received either corticosterone or vehicle injections for 21 consecutive days prior to behavioral testing in the forced swim, open-field, and predator odor tests. The corticosterone injections significantly increased depression-like behavior in the forced swim test in both male and female rats but had no significant effect on anxiety in the open-field test. In the predator odor test, the corticosterone injections significantly increased a subset of defensive behaviors in the male rats. These results suggest that repeated exposure to corticosterone increases depression-like behavior, with some effects on anxiety, and that male rats may be more affected than female rats by this manipulation. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Alcohol-induced conditioned taste aversions in chemically labyrinthectomized rats

Male rats were chemically labyrinthectomized (n = 22) by intratympanic injections of sodium arsanilate, and control rats (n = 15) received intratympanic injections of isotonic saline. All rats were tested for labyrinthine integrity and then adjusted to a 23 h.d-1 water deprivation schedule. Both labyrinthectomized and control rats were exposed to a conditioned taste aversion (CTA) procedure or a control procedure. The CTA technique involved pairing a novel saccharin taste with subsequent intraperitoneal injection of ethanol (1.5 g.kg-1; 15% solution). The control CTA procedure paired a novel saccharin taste with injections of isotonic saline. Following two conditioning trials and 3 d of water only, saccharin preference ratios were obtained in two-bottle choice tests (saccharin vs. water) over 4 consecutive days. Control rats conditioned with ethanol exhibited a strong CTA (p < 0.01) relative to control rats injected with saline. Labyrinthectomized rats drinking saccharin followed by ethanol injections showed a strong CTA (p < 0.01) if conditioning occurred 29-30 d post-labyrinthectomy. However, CTA's were not apparent in labyrinthectomized rats conditioned with ethanol 19 d post-labyrinthectomy. Thus, ethanol-induced CTA formation varied across the post-labyrinthectomy time period.     

Commitment to social deprivation and verbal conditioning.

Control Ss who experienced high prior deprivation of a reinforcing stimulus (approval) responded more with a reinforced response in a verbal conditioning situation than Ss less deprived. Other Ss committed themselves to undergoing postexperimental deprivation of social reinforcement after the same high prior social deprivation. A model suggested by dissonance theory predicted that such Ss who committed themselves for lower rewards would experience greater dissonance; the greater the dissonance, the more could Ss justify their decisions and reduce dissonance by reducing their motive for social reinforcement, consequently behaving in the conditioning situation as Ss who had low motivation for social reinforcement. As expected, experimental Ss in the High Dissonance condition who committed themselves for low reward ($1.00) responded less to social reinforcement, i.e., they showed a smaller increase in response strength of emission of verbal behavior than Control Ss or Low Dissonance Ss who committed themselves for high reward ($5.00). (19 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Institutionalization and the effectiveness of social reinforcement: A three-year follow-up study.

49 familial retarded children who had been tested on a simple 2-part satiation game 3 years earlier were retested on the same game. The children were divided into high and low preinstitutional social deprivation groups, and 2 reinforcement conditions were employed. On the original testing a positive relationship was found between social deprivation experienced and the effectiveness of social reinforcement (p     

A Functional Approach to the Assessment of Self-Mutilative Behavior.

This study applied a functional approach to the assessment of self-mutilative behavior (SMB) among adolescent psychiatric inpatients. On the basis of past conceptualizations of different forms of self-injurious behavior, the authors hypothesized that SMB is performed because of the automatically reinforcing (i.e., reinforced by oneself; e.g., emotion regulation) and/or socially reinforcing (i.e., reinforced by others; e.g., attention, avoidance-escape) properties associated with such behaviors. Data were collected from 108 adolescent psychiatric inpatients referred for self-injurious thoughts or behaviors. Adolescents reported engaging in SMB frequently, using multiple methods, and having an early age of onset. Moreover, the results supported the structural validity and reliability of the hypothesized functional model of SMB. Most adolescents engaged in SMB for automatic reinforcement, although a sizable portion endorsed social reinforcement functions as well. These findings have direct implications for the understanding, assessment, and treatment of SMB. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of Medial Septal Lesions on Action-Outcome Associations in Rats Under Conditions of Delayed Reinforcement.

In operant tasks, control rats maintain high response rates under positive contingencies, when the probability of reinforcement is greater following a response (contingent reinforcement) than during the absence of that response. However, as contingencies approach zero, response rates decrease. In this experiment, under immediate contingent reinforcement, rats with medial septal lesions reduced their response rates, just like controls, when contingencies were shifted from positive toward zero. However, the septal rats were less sensitive to this contingency shift, compared with controls, when there was a 5-s delay between lever presses and contingent reinforcements. This lesion effect appeared to be due to a failure of voluntary response memory, which impaired sensitivity to operant contingencies when there was a delay between action and outcome. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Disruption of appetite but not hunger or satiety following small lesions in the amygdala of rats.

In 5 experiments, discretely localized lesions were made in the amygdala of adult male albino Sprague Dawley rats to examine how specifically they might alter various measures of feeding behavior. Behavioral tests included spontaneous intake and body weight regulation, reactivity to saccharin and quinine solutions, conditioned taste aversion, the feeding response to food deprivation, the response to glucose gavage, and the response to dietary amino acid imbalance. Lesions in virtually all regions of the amygdala disrupted feeding behavior in some respect, but alterations in specific tasks were associated only with highly circumscribed brain damage. Body weight regulation, spontaneous food and water intake, and the responses to glucose gavage and long-term food deprivation were not altered by lesions in the amygdala. Results provide evidence that in the rat, the amygdala may play a greater role in appetite than in hunger or satiety. In particular, amygdaloid nuclei may participate in maintaining a negative bias in the reactivity to all appetitive stimuli. (64 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Importance of trials versus accumulating time across trials in partially reinforced appetitive conditioning.

Four experiments with rats examined partial reinforcement in appetitive conditioning. In Experiment 1, adding nonreinforced trials to a continuous reinforcement schedule slowed acquisition, whereas deleting reinforcers did not. Trial massing suppressed performance and learning. In Experiment 2, conditioning with a short conditioned stimulus (CS) was rapid, and partial reinforcement with a short CS was as effective as continuous reinforcement with equal accumulated time in the CS. In Experiment 3, conditioning was nevertheless influenced by the probability of reinforcement. In Experiments 3 and 4, conditioning was especially disrupted when nonreinforced trials preceded reinforced trials closely in time. The results underscore the importance of temporal variables in conditioning but are more consistent with trial-based accounts than time-accumulation accounts of conditioning. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The "social deprivation-satiation effect": An outcome of frequency or perceived contingency?

Evaluated the contributions of frequency and contingency of reinforcement to the deprivation-satiation phenomenon. 72 3rd and 4th graders heard the word good either twice (deprivation) or 16 (satiation) times either contingently upon some action on their part, contingently upon some action of the E's, or noncontingently (at random). This was followed by a discrimination test under continuous reinforcement with the word good. All Ss showed high performance except the group exposed to the high frequency of noncontingent reinforcement. A postexperimental interview revealed that all groups except the high-frequency noncontingent group had interpreted the E's approval words as having been contingent on their behavior during treatment. Results support E. Y. Babad's (1972) thesis that the perceived contingency of reinforcement is a more powerful determinant of its subsequent reinforcement effectiveness than is its frequency per se. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Two forms of spatial memory: A double dissociation between the parietal cortex and the hippocampus in the rat.

Two variants of a continuous recognition training procedure were designed in order to query 2 forms of spatial memory. A continuous reinforcement condition (reflecting perceptual memory) and a differential reinforcement condition (reflecting episodic-like memory) were used to test rats on a 12-arm radial maze. After total hippocampal lesions, rats demonstrated intact performance on the continuous reinforcement condition, but impaired performance on the differential reinforcement condition. After parietal lesions, rats demonstrated the reverse pattern of performance: impaired performance on the continuous reinforcement condition and intact performance on the differential reinforcement condition. Thus, a double dissociation appears to exist between parietal cortex and hippocampus for the continuous reinforcement condition (reflecting perceptual memory) versus the differential reinforcement condition (reflecting episodic memory) for spatial location information. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Cocaine-induced suppression of saccharin intake: A model of drug-induced devaluation of natural rewards.

In Experiment 1, water-deprived Sprague-Dawley rats were given 5 min access to saccharin. This tube retracted, an empty tube advanced, and the rats were given 1 hr to lick the empty tube on a fixed-ratio 10 lick contingency to self-administer saline or cocaine (0.33 mg/infusion) via an intravenous catheter. The results showed that rats avoided intake of saccharin after saccharin-cocaine pairings and that greater avoidance of the gustatory cue was associated with greater cocaine self-administration. In Experiment 2, a similar dose-response function was obtained with either the empty tube or a lever as the operant. In Experiment 3, avoidance of the saccharin cue and the propensity to self-administer cocaine were maintained after at least 1 month of abstinence. As such, this paradigm may be useful as a model of cue-induced craving and drug-induced devaluation of natural rewards. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The effects of acquisition training schedule on extinction and reinstatement of cocaine self-administration in male rats.

Partial reinforcement is known to increase resistance to extinction (Rn) relative to training with continuous reinforcement. This phenomenon, referred to as the partial reinforcement extinction effect, is one of the most robust in learning and conditioning studies. Experiment 1 investigated manipulations known to affect the partial reinforcement extinction effect and determined their possible relevance for drug use patterns. Male rats received intravenous cocaine self-administration training under partial reinforcement (FR-10) training or continuous reinforcement (FR-1) conditions with either a low (0.25 mg/kg infusion) or a high cocaine dose (1.00 mg/kg infusion). Animals were placed on an extinction (recurrent nonreward) schedule for 10 days (1-hr sessions) prior to being tested for cue-induced reinstatement (single 2-hr session). Experiment 2 involved acquisition of cocaine self-administration under FR-1 conditions of short training (15 days) or extended training (30 days) with a low dose (0.25 mg/kg infusion) or a medium dose (0.50 mg/kg infusion) of cocaine reward prior to extinction or reinstatement. Experiment 1 showed that rats trained with FR-10-high dose outcomes exhibited greater Rn than the remaining groups. Additionally, FR-10-high dose and FR-10-low dose rats were more likely to return to active drug seeking during the reinstatement test. In Experiment 2, rats trained under FR-1-medium dose conditions were more persistent during extinction following short acquisition training than comparable rats experiencing extended acquisition training. The reinstatement test was conducted following extinction, in which it was observed that overtraining under FR-1-medium dose reward schedules resulted in a decrease in the tendency to return to active drug seeking. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Motivational state regulates the content of learned flavor preferences.

Rats acquired a preference for an aqueous odor (almond) presented in simultaneous compound with sucrose. Separate presentations of saccharin reduced this preference in rats with ad-lib access to food during training or at test, but not in rats that were hungry during both training and test. In contrast, separate presentations of sucrose reduced the preference for the almond irrespective of deprivation state during training and test. We interpret the results to mean that a hungry rat forms odor–taste and odor–calorie associations, and its motivational state on test determines which of these associations controls the preference. In contrast, a rat that is not hungry during training only forms an odor-taste association, and its performance on test is independent of its level of hunger. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Conditioned adrenocortical steroid elevations in the rat

An illness-induced taste aversion paradigm was used to condition an elevation in plasma corticosterone level. Rats were injected with cyclophosphamide 30 min after consuming a novel saccharin drinking solution. Plasma corticosterone levels were measured before conditioning to determine unconditioned steroid levels and 3 and 6 days after training when conditioned and nonconditioned animals were provided with the saccharin solution or plain water, or were left deprived. The pairing of saccharin and cyclophosphamide was effective in inducing a passive avoidance response. There were no differences between the steroid levels of conditioned and nonconditioned animals supplied with plain water or those that remained deprived, although deprivation increased corticosterone levels. Nonconditioned rats presented with saccharin had steroid levels that did not differ from control values. Conditioned animals presented with saccharin showed an elevation in steroid level which was significantly greater than that observed in any other group. Comparable results were obtained when LiCl was used as the unconditioned stimulus.     

Multielemental stimulus control: Effects of saccharin concentration on a discriminated morphine-saccharin taste aversion.

The effects of saccharin concentration on the stimulus control by a compound stimulus consisting of morphine, saccharin (0.01, 0.03, or 0.10%, wt/vol), and a ball bearing drinking nozzle in a discriminated taste aversion (DTA) procedure were examined in rats (Rattus norvegicus). In paired rats injections of lithium followed presentation of this compound stimulus, whereas in unpaired rats saline injections followed this stimulus. DTA acquisition was more rapid at higher saccharin concentrations. In testing with each individual stimulus element, stimulus control was clearly exerted by all 3 stimulus elements. When another stimulus element was presented jointly with saccharin, behavioral control was similar to that of saccharin alone. Behavioral control by saccharin increased with saccharin concentration. However, behavioral control by the 2 other stimulus elements was relatively unaffected when the saliency of the saccharin element was increased. (PsycINFO Database Record (c) 2010 APA, all rights reserved)