Conditioned ethanol aversion in rats induced by voluntary wheel running,forced swimming,and electric shock: An implication for aversion therapy of alcoholism

This study was planned to demonstrate rats’ acquisition of aversion to ethanol solution consumed before voluntary running, forced swimming, or electric shock delivery. Wistar rats under water deprivation were allotted to four groups of eight rats each, and all rats were allowed to drink 5% ethanol solution for 15 min. Immediately after the ethanol drinking, rats of Group Run were put into the individual running wheels for 15 min, those of Group Swim were put into the individual swimming pools for 15 min, those of Group Shock received electric shocks for 15 min (15 0.45-mA shocks of 0.7s with the intershock interval of 1 min) in the individual small chambers, and those of Group Control were directly returned back to the home cages. This procedure was repeated for six days, followed by a two-day choice test of ethanol aversion where a bottle containing 5% ethanol solution and a bottle of tap water were simultaneously presented for 15 min. In the test, Groups Run, Swim, and Shock drank ethanol solution significantly less than tap water, while Group Control drank both fluids equally. The effects of running, swimming, and shock were equivalent. The successful demonstration of acquired ethanol aversion induced by exercise (running and swimming) or shock in rats suggests an avenue for clinical application of exercise and shock treatments for human alcoholics, though there are many issues to be resolved before the practical use.     

Analysis of discriminative control by social behavioral stimuli

Visual discriminative control of the behavior of one rat by the behavior of another was studied in a two-compartment chamber. Each rat's compartment had a food cup and two response keys arranged vertically next to the clear partition that separated the two rats. Illumination of the leader's key lights signaled a “search” period when a response by the leader on the unsignaled and randomly selected correct key for that trial illuminated the follower's keys. Then, a response by the follower on the corresponding key was reinforced, or a response on the incorrect key terminated the trial without reinforcement. Accuracy of following the leader increased to 85% within 15 sessions. Blocking the view of the leader reduced accuracy but not to chance levels. Apparent control by visual behavioral stimuli was also affected by auditory stimuli and a correction procedure. When white noise eliminated auditory cues, social learning was not acquired as fast nor as completely. A reductionistic position holds that behavioral stimuli are the same as nonsocial stimuli; however, that does not mean that they do not require any separate treatment. Behavioral stimuli are usually more variable than nonsocial stimuli, and further study is required to disentangle behavioral and nonsocial contributions to the stimulus control of social interactions.     

Lick-trading by rats: on the substitutability of dry, water, and saccharin tubes.

Thirsty rats licked two metal tubes: a water tube paired with another water tube, with saccharin, or with a dry tube. For each pair, a multipoint baseline function was measured by offering free access to one tube throughout each session, and free or restricted access to the other. The three resulting baseline functions showed the members of each pair to be mutual substitutes: When access to either tube was restricted, the rats made more licks at the other. A linear function identified the two water tubes as perfect substitutes. Convex functions identified the members of the saccharin-water and the dry-water pair as imperfect substitutes. Each pair was also tested under several reciprocal fixed-ratio schedules that required instrumental licking of either tube for contingent access to the other. The resulting schedule functions showed the members of each pair to be perfect substitutes: Water licks decreased linearly as licks at the other water tube, the saccharin, or the dry tube increased, in agreement with a conservation model of instrumental performance. Baseline and schedule functions, indistinguishable in the water-water pair, indicated a schedule facilitation of dry-tube licking in the dry-water pair and of water-tube licking in the saccharin-water pair.     

Some parameters of behavioral contrast and allocation of interim behavior in rats

Two experiments examined the effects of baseline reinforcement rate and component duration on behavioral contrast and on re-allocation of interim behavior in rats. Positive behavioral contrast occurred during multiple variable-interval 10-second extinction (VI 10 EXT) after a multiple VI 10 VI 10 baseline condition, but not during multiple VI 60 EXT following multiple VI 60 VI 60 baseline. Component duration had no significant effect on contrast. These results differed from those found in studies of pigeons' key pecking. Contrast was accompanied by an increased rate of drinking in the changed component, but drinking in the constant component did not decrease. These results are not consistent with the competition theory of contrast, but are consistent with the predictions based on the matching law. However, no current theory seems to account for all instances of behavioral contrast.     

Substitutability between conditioned and primary reinforcers in discrimination acquisition.

Rats and pigeons were trained on a series of reversals of a conditional simultaneous discrimination. The percentage of reinforcement for correct trials was varied across reversals. When nonreinforced correct trials produced the same feedback as incorrect trials, the number of errors to reach an acquisition criterion was greater for smaller percentages of reinforcement, but the number of reinforcers required was either approximately constant or smaller for the smaller percentages. When a stimulus paired with food (the conditioned reinforcer) was added on nonreinforced correct trials, both measures were substantially decreased. When the same stimulus was presented, but without a history of food pairing, learning rate was similar to when no stimulus was presented on nonreinforced trials. The results provide direct evidence that conditioned reinforcers may substitute, although imperfectly, for a primary reinforcer, and that pairing with the primary reinforcer is a necessary condition for such substitutability to occur.     

Response specificity in animal timing.

The stimuli that control responding in the peak procedure were investigated by training rats, in separate sessions, to make two different responses for food reinforcement. During one type of session, lever pressing was normally reinforced 32 s after the onset of a light. During the other type of session, chain pulling was normally reinforced either 8 s after the onset of one auditory cue or 128 s after the onset of a different auditory cue. For both types of sessions, only the appropriate manipulandum was available, and 20% of the trials lasted 240 s and involved no response-contingent consequences. Rats were then tested with the auditory cues in the presence of the lever and the light in the presence of the chain. If the time of reinforcement associated with each stimulus was learned, response rates should peak at these times during transfer testing. However, if a specific response pattern was learned for each stimulus, little transfer should occur. The results did not clearly support either prediction, leading to the conclusion that both a representation of the time of reinforcement and the rat's own behavior may control responding in this situation.     

医学研究生动物实验伦理认知考察：以雄性连体鼠受孕为例

动物实验是医学研究与教育中不可或缺的环节,也是培养其科研伦理意识的实践途径。对410名医学研究生的研究结果显示：56.8%的人称不应开展雄性连体鼠受孕实验,58.1%的人称此实验违背了3R原则,76.3%的人称此类研究需要接受伦理委员会的伦理审批。被调查医学研究生的动物实验伦理认知情况尚好。因此建议医学院校和科研院所要加强动物实验伦理教育,提高医学研究生和科研人员的伦理意识和伦理决策能力,健全伦理审查制度,优化医学科技伦理治理环境。     

An eight-alternative concurrent schedule: foraging in a radial maze.

In two experiments conducted in an eight-arm radial maze, food pellets were delivered when a photocell beam was broken at the end of each arm via a nose poke, according to either fixed-interval or random-interval schedules of reinforcement, with each arm providing a different frequency of reinforcement. The behavior of rats exposed to these procedures was well described by the generalized matching law; that is, the relationships between log behavior ratios and log pellet ratios were approximated by linear functions. The slopes of these log-log functions, an index of sensitivity to reinforcement frequency, were greatest for nose pokes, intermediate for time spent in an arm, and least for arm entries. Similar results were obtained with both fixed-interval and random-interval schedules. Addition of a 10-s changeover delay in both experiments eliminated the slope differentials between nose pokes and time spent in an arm by reducing the slopes of the nose-poke functions. These results suggest that different aspects of foraging may be differentially sensitive to reinforcement frequency. With concurrent fixed-interval schedules, the degree of temporal control exerted by individual fixed-interval schedules was directly related to reinforcement frequency.     

Preference for signaled over unsignaled shock schedules: Ruling out asymmetry and response fixation as factors

Experiment 1 tested whether a “symmetrical” choice procedure yields results different from those previously reported using the “unidirectional” standard changeover procedure (e.g., Badia & Culbertson, 1972). Subjects could change at any time from unsignaled to signaled shock by pressing a lever and from signaled to unsignaled shock by pressing a second lever. Results were identical to those of the standard procedure and showed that the standard procedure is fully adequate. Experiment 2 tested whether choice of high density signaled shock over low-density unsignaled shock (Badia, Coker, & Harsh, 1973) resulted from initial training with equal-density schedules. Subjects were trained and tested with signaled shock twice as dense as unsignaled shock. Three of four subjects strongly preferred the signaled condition, thus ruling out carry-over and “response fixation” as alternative explanations.     

Signal modality and choice between signaled and unsignaled food

Choice between signaled and unsignaled response-independent food schedules was assessed in three experiments using a commitment procedure. In Experiment 1, subjects tested with a 5-s visual signal consistently changed from the signaled to the unsignaled schedule. Changing from the unsignaled to the signaled schedule was observed only occasionally and only at low levels. The same outcome was observed in Experiment 2 with different types of visual signals and with different stimulus combinations identifying the signal period, the signal-absent period, and the unsignaled schedule. In Experiment 3 the visual signal was replaced with an auditory signal for four of the subjects tested in Experiment 2. The subjects then changed from the unsignaled to the signaled schedule or showed a substantial reduction in choice for the unsignaled schedule. The data were assessed using a conditioned-reinforcement interpretation of choice.