Access Scheduling Research Articles

The meal pattern of rats shifts from postprandial regulation to preprandial regulation when only five meals per day are scheduled

In order to investigate whether an observed difference in the meal patterns of rats and humans may be due to constraints that humans have on the timing of meals and their large but infrequent meal pattern, rats had similar constraints imposed on their meal intake. Fifteen male Long-Evans rats were monitored in five individual enclosed chambers equipped with pellet sensing eatometers for three fourteen-day data collection periods. Both groups were monitored in a baseline ad lib condition, then one group (n=7) was allowed access to food only once every two hours, while the second group (n=8) was allowed to access only five times per day. Both groups were then monitored for a second ad lib baseline period. The imposition of both schedules reduced meal frequencies and estimated premeal stomach contents, and increased meal sizes and estimated postmeal stomach contents. The imposition of the five meal per day, but not the twelve meal per day schedule of meal access, eliminated the significant relationships between meal size and the postmeal interval evident during baseline conditions and produced significant relationships between meal size and the premeal interval and estimated premeal stomach content, not seen during baseline conditions. The rats under the five meal per day access schedule showed a preprandial pattern of intake very similar to that previously observed in humans eating ad lib. It was concluded that the preprandial pattern, typical of humans, is characteristic of intake involving large infrequent meals which produce stomach filling to an upper limiting threshold. The postprandial pattern, typical of rats, is characteristic of intake involving small frequent meals that are initiated when the stomach empties to a lower threshold. A peripheral, stomach capacity, model then, can be used to explain both the preprandial and the postprandial patterns. Which pattern is used depends upon environmental conditions.

Tolerance and cross-tolerance to theophylline-induced stimulation of locomotor activity in rats

Rats treated chronically with caffeine become tolerant to caffeine-induced stimulation of locomotor activity and cross-tolerant to theophylline. This study was performed to determine if the cross-tolerance between these two methylxanthine drugs is symmetrical. Symmetrical cross-tolerance produced by two different drugs implies a common underlying mechanism of action. Separate groups of rats were given scheduled access to drinking bottles containing either drug-free tap water or 1.0mg/ml theophylline solution. Daily theophylline control and theophylline-treated groups for 5 drugs: the methylxanthines theophylline and caffeine, a nonxanthine psychomotor stimulant, d -amphetamine, and the adenosine analogs R(-)-N 6-2-(phenylisopropyl) adenosine and 5′-(N-ethyl) carboxamidoadenosine. All drugs were injected i.p. and locomotor activity was measured for 30 min beginning 35 min later. Rats that were maintained chronically on theophylline were completely tolerant to the locomotor activity stimulant effects of acutely administered theophylline and cross-tolerant to caffeine-induced stimulation of locomotor activity. In contrast, both control and treated groups were fully responsive to the stimulant effects of d -amphetamine. Low doses of the adenosine analogs produced stimulation of locomotor activity in both groups of rats. Higher doses produced a dose-dependent depression of locomotor activity in control rats; curves for the theophylline-treated rats were shifted to the right of the control curves. Thus, adenosine antagonist activity of theophylline remained evident at a time of complete tolerance to the stimulant effect of the drug on locomotor activity.

Alcohol preference in rats lacking gustatory neocortex

Ingestion of alcohol solutions (in concentrations from 0.5 to 12% v/v) was examined in three experiments where rats lacking gustatory neocortex (GN) were compared with intact and control lesion rats. Two experiments tested alcohol consumption during a restricted schedule of fluid access with one or two bottle tests. The last experiment involved testing with continuous access to water and alcohol solutions in two bottle tests. Subgroups of rats in each experiment were presented with either an ascending or descending order of concentrations. In all experiments, GN rats consumed less total fluid during testing (relative to control rats). In general, GN rats exhibited similar patterns of alcohol consumption as that found in control rats. Where differences between GN rats and control rats were found, GN rats consumed more alcohol than control rats during tests with restricted fluid access. During continuous fluid access, however, no significant differences between GN rats and control rats were found.

Effects of scheduled access on ethanol intake by the alcohol-preferring (P) line of rats

The effects of scheduling the availability of ethanol on its voluntary consumption by the selectively bred alcohol-preferring P rats were examined under three conditions: unrestricted 24 hr/day access (Condition A), access limited to a continuous 4 hr/day (Condition B), and access limited to 1 hr every 3 hr, 4 times/day (Condition C). Food and water were always available. Daily alcohol intakes (mean±SEM) with Conditions A, B and C were 6.9±0.2, 2.1±0.2 and 4.4±0.2 g/kg, respectively, while the intake per hour of availability increased from 0.3±0.03 under Condition A to 1.1±0.4 g/kg under condition C. The amount of ethanol consumed per drinking episode under Conditions A, B and C were 1.1±0.1, 2.1±0.2 and 1.1±0.03 g/kg, respectively. Mean blood alcohol concentrations (BACs), determined periodically during the dark cycle of Condition A and five minutes after drinking episodes under Conditions B and C, were 59±10, 61±7 and 62±7 mg%, respectively. When unlimited access was reinstated after Condition C, daily alcohol consumption returned to a level similar to that under the initial Condition A (7.2±0.5 g/kg). When the ethanol concentration was increased from 5 to 20% (v/v) under Condition C, the amount of ethanol consumed per episode at 5% was significantly less than at the 10, 15 and 20% concentrations, and the volume consumed was significantly lower at the 20% concentration than at the 5, 10 and 15% concentrations. However, mean BAC measured five minutes after cessation of drinking did not differ across the four concentrations (rnage: 50±7 to 62±7 mg%). The findings indicate that BAC is a major factor that limits ethanol intake in P rats Scheduling the availability of ethanol to one episode per day for four hours enhances alcohol intake when calculated per drinking episode but not per day. Scheduling also does not increase intake during subsequent unrestricted access in the P rats.

Voluntary ethanol consumption in rats: an examination of blood/brain ethanol levels and behavior.

The temporal pattern of food, water, and ethanol consumption was examined in rats maintained on a 24-hr ethanol access schedule. These data demonstrated that rats consume ethanol in discrete, short bouts mainly during the lights-out cycle. Simulation of a single ethanol drinking bout was carried out by limiting ethanol access to a short time period each day. Detectable levels of blood and brain ethanol were observed following these individual drinking bouts. Behavioral evidence is provided indicating that rats drink ethanol in quantities sufficient to produce pharmacological effects.

Circadian wheel-running activity of rats under schedules of limited daily access to salt.

Schedules of limited daily access to food result in 'anticipatory' activity preceding each daily feeding. It is well-established that such food-anticipatory activity depends on a food-entrainable circadian timing mechanism. In the present study, we sought to extend the generality of these results by maintaining rats in running wheels under schedules which provided access to salt solutions or to salty food for 2 hr each day. The animals were subjected to dietary, pharmacological and surgical treatments that promote salt appetite. However, we found no evidence for daily salt-anticipatory wheel running activity in any condition.

Dataflow Resource Managers and Their Synthesis from Open Path Expressions

The control of concurrent access to shared resources is an important feature of both centralized and distributed operating systems. In conventional systems, exclusive access is the rule while concurrent access is the exception. Dataflow computer systems, along with an applicative style of programming, provide an execution environment in which this philosophy is reversed. In these latter systems, it is necessary to reexamine the manner in which synchronization of access to shared resources is specified and implemented. A basic design for a dataflow resource manager is reviewed, illustrating the clear separation between access mechanism and scheduling policy. The semantics of the access mechanism is based solely on the principle of data dependency. Specifications are presented for a general scheduler to further constrain or order accesses to the resource. Using ``open path expressions'' as a very high-level specification language for synchronization, it is shown how to automatically synthesize a scheduler as a distributed network of communicating modules.

Control of behavior by intravenous nicotine injections in human subjects

Results are summarized from a series of studies in which procedures used to assess the reinforcing and aversive properties of drugs in animals, were extended to a human paradigm. Human volunteers were tested using drug self-administration and avoidance procedures, whereby pressing a lever under a fixed-ratio schedule resulted either in the IV injection of nicotine or in the avoidance of programmed IV injections of nicotine, respectively. Nicotine was found to maintain responding that produced its injection under certain conditions, and to maintain responding that avoided its injection under other conditions. Nicotine produced the same constellation of stimulus properties whether functioning as a positively or negatively reinforcing event. These functional properties of nicotine may be determined by schedule of access to nicotine, dose of nicotine, and past history of the subject.

Symmetrical effect of pre-exposure between alcohol and morphine on conditioned taste aversion

It has previously been reported that pre-exposure to a psychoactive drug can block the conditioned taste aversion associated with that drug. This study was an attempt to investigate alcohol-morphine interactions using this pre-exposure paradigm. After two weeks of adaptation to a schedule of daily 30-minute access to water, rats were pre-exposed to morphine, ethanol, or the respective vehicle control every second day for three days before (Days 1,3,5) and after the first conditioning day (Days 8,10,12). On conditioning days (Days 7,14), animals were first presented with a saccharin solution for 30 minutes following which animals that were pre-exposed to morphine were injected with ethanol while those pre-exposed to ethanol were administered with morphine. Saccharin was again presented on three more occasions (Days 21,28,35) without drug injection. Using the percent change in saccharin consumed from the first presentation as a measure of aversion, it was found that pre-exposure to morphine blocked ethanol conditioned taste aversion. Similarly, animals pre-exposed to ethanol showed less aversion to the saccharin paired with morphine. This is the first demonstration of a symmetrical relationship between alcohol and the opiates.

Complete, reversible, drug-specific tolerance to stimulation of locomotor activity by caffeine

The development of tolerance to caffeine-induced stimulation of locomotor activity was evaluated in rats maintained chronically on average daily doses of 160 mg/kg or more of caffeine by the method of scheduled access to drinking water containing the drug. Dose-response curves were determined for caffeine (6.25–100 mg/kg) and d -amphetamine (0.39–6.4 mg/kg) during chronic drug treatment. In addition, the caffeine curve was redetermined 2–3 weeks after removal of the drug from the drinking water. A control group that had scheduled access to drug-free tap water was also tested. Caffeine produced dose-related increases in the locomotor activity of the controls but failed to modify locomotor activity of the chronic caffeine group. In contrast, d -amphetamine increased locomotor activity of both groups comparably. Spontaneous locomotor of the chronic caffeine group was reduced significantly for 4 days after drug-free tap water was substituted for the caffeine solution. The return of spontaneous locomotor activity to baseline values was associated with restored sensitivity to caffeine-induced stimulation of locomotor activity. Thus, chronic administration of caffeine to rats results in the development of tolerance to caffeine-induced stimulation of locomotor activity that is virtually complete, pharmacologically specific, and fully reversible when drug treatment is stopped. Decreases in spontaneous locomotor activity after abrupt termination of chronic caffeine administration follow a time course consistent with a drug withdrawal syndrome.

The effects of β-phenylethylamine and phenylethanolamine on water intake in rats: A temporal analysis

1. 1. Hale Wistar rats were adapted to a restricted access schedule of water intake. 2. 2. For each animal overall water intake (m1) and number of licks per minute were measured over the period of access to water. 3. 3. The effects of various doses of β-phenylethylamine and of phenylethanolamine were assessed in separate groups of animals. 4. 4. In terms of effects on overall consumption the two amines were equipotent in suppressing water intake. The local analysis revealed, however, that β-phenylethylamine was more potent, but had a much shorter duration of action than phenylethanolamine.

Schedule of Events

Journal of AndrologyVolume 3, Issue 1 p. 2-4 Free Access Schedule of Events First published: January‐February 1982 https://doi.org/10.1002/j.1939-4640.1982.tb00642.xAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat Volume3, Issue1January‐February 1982Pages 2-4 RelatedInformation

Locomotor activity in morphine-dependent and post-dependent rats

The effects of morphine and naloxone were compared on the locomotor activity of nondependent, morphine-dependent, and post-dependent rats. Dependence was induced and maintained for 30 weeks by scheduled access to 0.05% morphine solution for 10 min every 6 hr. Locomotor activity in nondependent and dependent animals was increased by low doses of morphine and reduced by higher doses. Both components were antagonized by naloxone. Chronic morphine treatment produced marked tolerance to the depressant effect of high morphine doses, but not to the stimulant effect of low doses. Post-dependent animals remained tolerant to the depressant effect of high doses of morphine. The development of tolerance to the depressant but not to the stimulant effect of morphine in dependent and post-dependent animals suggests that different neuronal substrates mediate morphine-induced stimulation and depression of locomotor activity. Abrupt or naloxone-precipitated withdrawal generally disrupted locomotor activity in dependent rats. Naloxone alone also decreased activity in post-dependent animals. Thus, chronic morphine administration produces long-lasting changes in the sensitivity of dependent and post-dependent rats to the effects of morphine and naloxone on locomotor activity.

Taste reactivity in rats following lesions of the zona incerta or amygdala

Rats with amygdala lesions (n=12) and rats with zona incerta lesions (n=12) were compared to normal rats (n=12) in their response to various taste stimuli. Five concentrations each of sucrose, sodium chloride, quinine hydrochooride, and hydrochloric acid were presented to all animals in single bottle tests during a schedule of restricted fluid access. Results indicated that both groups of rats with lesions had significantly lower baseline water consumption than normal rats. Using taste consumption measures expressed as a percent of water baseline, it was found that zona incerta lesions did not significantly alter normal taste reactivity. Animals with zona incerta lesions did fail to show normal habituation to a 0.0001 M quinine solution over repeated presentations. Lesions of the amygdala resulted in an increase in consumption of the acid solutions; consumption of sucrose, quinine, and sodium chloride was normal across concentrations. Amygdala damaged rats failed to show normal neophobia when first presented with the 0.0001 M quinine solution. It was concluded that taste response functions of rats with lesions of the zona incerta or amygdala remain essentially normal following surgery but that subtle changes in reactivity do occur, particularly with regard to neophobia.

Schedule-controlled behavior in the morphine-dependent and post-dependent rat

Chronic morphine treatment has been reported to induce long-lasting changes in the responses of animals to the subsequent administration of morphine or narcotic antagonists. However, there have been few systematic studies in which the effects of morphine or narcotic antagonists have been compared in the same group of animals before, during, and after chronic morphine administration. Rats were trained to press a lever on a variable interval (1 min) schedule of food presentation and dose-response curves were determined for morphine (0.3--30 mg/kg) and naloxone (0.003--10 mg/kg) in the same group of animals prior to, during, and following morphine dependence. Dependence was induced and maintained by scheduled access to 0.05% morphine drinking solution for 10 min every 6 h. Response rates and fluid intake remained constant over the 9 month study. The dose-response curves for morphine and naloxone in predependent and dependent animals were similar to those previously reported in studies using other schedules of reinforcement and different techniques for establishing morphine dependence: chronic morphine treatment produced a threefold decrease in the effect of morphine and a dramatic increase in the effectiveness of naloxone in decreasing response rate. The altered sensitivity of dependent rats to morphine and naloxone was completely reversed in the post-dependent animals, within 4 weeks after the withdrawal of morphine. Scheduled access to a morphine solution affords a simple means of maintaining morphine-tolerant and dependent animals for long-term behavioral studies.

Narcotic-reinforced responding: A rapid evaluation procedure

Rhesus monkeys were conditioned to lever press for intravenous injections of codeine. The self-injection behavior was brought under the control of a schedule of drug delivery and access to the codeine schedule was made available twice each day. Subsequently, a variety of doses of codeine and saline were compared to the dose used to condition and maintain self-injection responding. Each change in drug condition was maintained for only a single experimental session. The procedure is recommended for rapid evaluation of drugs for their capacity to reinforce self-injection behavior.

Aftereffects of lithium-conditioned stimuli on consummatory behavior in the presence or absence of the drug.

Drinking is increased by prior exposure to lithium-conditioned stimuli. Experiment 1 showed that this phenomenon is not an artifact of testing subjects with a novel, palatable drinking fluid and also showed that lithium-conditioned olfactory stimuli produce a biphasic change in drinking, with drinking suppressed at the start of exposure to the conditioned stimulus (CS) and enhanced a long time after CS onset or exposure. Experiment 2 showed that the increased drinking aftereffect of lithium-conditioned stimuli is not a result of the instrumental reinforcement of the drinking response by the scheduling of water access following drug injections during conditioning, and Experiments 3, 4, and 5 showed that the increased drinking effect occurs even if subjects are injected with lithium prior to the test session. The results of Experiments 3 and 5 alos showed that lithium administration and exposure to lithium-conditioned stimuli have independent and opposite aftereffects: Lithium disrupts drinking, whereas prior exposure to lithium-conditioned stimuli increases consumption. The relevance of conditioned opponent and compensatory processes to the findings is discussed.

Systematic patrolling and orderly behaviour of rats during recovery from deprivation

Two experiments examined the behaviour of rats during recovery from food or water deprivation. Both in their home cages and in a residential environment (plus-maze), rats systematically reexplored their familiar surroundings, particularly after they had partly satisfied their deficits and before they settled again to rest. Partial recovery from deprivation apparently ‘disinhibited’ exploration. The pattern of such patrolling in the plus-maze was, at least, a second-order process; the identity of an arm visited was influenced by the identity of the previous two arms visited within the same activity bout. Adaptation to the schedule of restricted access to food and water was accompanied by changes in the parameters of activity bouts and in the sequences of movements about the mazes, but not by an increase in total time spent ‘active’. Although rats directed their initial behaviour more to remedying their immediate deficits, the level of patrolling was nevertheless maintained.

Adjunctive behavior and smoking induced by a maze solving schedule in humans

Adjunctive behavior has been reported as occurring in a variety of species and has been described primarily as a phenomenon of excessive drinking in the rat (schedule induced polydipsia). In an earlier study [9] it was shown that adjunctive behavior occurs in adult human subjects with an FI 60 schedule controlling game playing on a poker machine. In the present study 20 subjects, all University personnel or students, were paid to participate in an experiment where they were required to solve a maze under conditions of scheduled access (8 sec maze drawing). Four subjects were tested with 8, 60, 120 and 300 sec intervals, and 4 with FI 120 on all test sessions. An additional 12 subjects, who were all habitual smokers, were tested with FI 60 sec intervals on all test sessions. A comparison with baseline conditions, consisting of either listening to a tape recording or continuous problem solving, showed an increase in the amount of subjects' motor activity under schedule conditions. There was a significant increase in movement scores with an increase in schedule length, but no increase with repeated scheduled trials of equal duration. The amount of smoking during test sessions was significantly greater than during smoking baseline sessions. Allowing the subject to smoke or not to smoke on maze schedule sessions made no difference to the movement scores. Eight of the subjects were also given instructions to keep still. These instructions had no effect in reducing the amount of activity. These data show that the scheduling of cognitive tasks can also lead to adjunctive behavior.

Feeding patterns in rats on restricted access schedules: Palatability, bulk, and other determinants of intake

Rats were adapted to 2 h or 4 h restricted daily feeding schedules. The feeding patterns were continuously recorded using a strain gauge. Different groups received different powdered foods, and some groups were switched to different diets at a late stage of adaptation to the original diet. Feeding behavior became continuous throughout a 4-h access when a cellulose diluted diet was presented. In contrast, calorically denser diets were taken in two or three discrete meals during the session. Bitter foods were eaten slowly. The results show that a consideration of different momentary feeding patterns can give more useful insights than a simple measure of the total amount ingested during the session. It is suggested that oral satiety factors or mechanical constraints may pose an upper limit when feeding calorically diluted diets, while postingestive events may limit the intake of denser diets. Liquid diets may be subject to still different constraints.