Relaxation measured by EMG as a function of vibrotactile stimulation

Key pecking of two pigeons was maintained under a multiple schedule of food presentation. In the presence of one keylight stimulus responding produced food according to a fixed-interval 5-min schedule. Additionally, during this component, each 50th response produced electric shock. When a different keylight stimulus was present, key pecking resulted in food delivery under a variable-interval 3-min schedule. Responding was suppressed by shock presentation (punishment) but was still positively accelerated throughout each fixed-interval cycle; steady response rates occurred during the alternate component when only the variable-interval schedule was in effect. Overall rates of punished responding were largely unchanged with d-amphetamine (0.1-3.0 mg/kg); unpunished responding was generally either increased slightly or was decreased. Pentobarbital and chlordiazepoxide (1.0-17.0 mg/kg) administered alone increased both punished and unpunished responding at most doses. Combinations of d-amphetamine with either pentobarbital or chlordiazepoxide produced increases in punished responding that exceeded those obtained with either of these drugs alone. The combined effects of d-amphetamine and either pentobarbital or chlordiazepoxide on unpunished responding depended on the individual dose combinations. Combinations of d-amphetamine with pentobarbital or chlordiazepoxide produced effects on both punished and unpunished responding that differed substantially from those obtained when any of these drugs were administered separately.     

Cleavage experiments with deoxythymidine 3'',5''-bis-(p-nitrophenyl phosphate) suggest that the homing endonuclease I-PpoI follows the same mechanism of phosphodiester bond hydrolysis as the non-specific Serratia nuclease

The present study examined the effects of morphine in pigeons responding under a progressive-ratio 25 schedule of food delivery. Morphine initially reduced response rates and breaking points. With chronic exposure, tolerance developed to these effects. The magnitude of the observed tolerance was not obviously different from that previously reported under a PR 5 schedule of food delivery. In addition, when drug effects were compared under the fixed-ratio 25 and fixed-ratio 100 components comprised by the progressive-ratio schedule, comparable tolerance was observed. Although prior studies using other procedures have shown that ratio size modulates the development of tolerance to morphine and other drugs, the present data suggest that this relation is constrained, and is not easily observed under progressive-ratio schedules.     

Mechanisms underlying the effects of unsignaled delayed reinforcement on key pecking of pigeons under variable-interval schedules

Three experiments were conducted to test an interpretation of the response-rate-reducing effects of unsignaled nonresetting delays to reinforcement in pigeons. According to this interpretation, rates of key pecking decrease under these conditions because key pecks alternate with hopper-observing behavior. In Experiment 1, 4 pigeons pecked a food key that raised the hopper provided that pecks on a different variable-interval-schedule key met the requirements of a variable-interval 60-s schedule. The stimuli associated with the availability of the hopper (i.e., houselight and keylight off, food key illuminated, feedback following food-key pecks) were gradually removed across phases while the dependent relation between hopper availability and variable-interval-schedule key pecks was maintained. Rates of pecking the variable-interval-schedule key decreased to low levels and rates of food-key pecks increased when variable-interval-schedule key pecks did not produce hopper-correlated stimuli. In Experiment 2, pigeons initially pecked a single key under a variable-interval 60-s schedule. Then the dependent relation between hopper presentation and key pecks was eliminated by arranging a variable-time 60-s schedule. When rates of pecking had decreased to low levels, conditions were changed so that pecks during the final 5 s of each interval changed the keylight color from green to amber. When pecking produced these hopper-correlated stimuli, pecking occurred at high rates, despite the absence of a peck-food dependency. When peck-produced changes in keylight color were uncorrelated with food, rates of pecking fell to low levels. In Experiment 3, details (obtained delays, interresponse-time distributions, eating times) of the transition from high to low response rates produced by the introduction of a 3-s unsignaled delay were tracked from session to session in 3 pigeons that had been initially trained to peck under a conventional variable-interval 60-s schedule. Decreases in response rates soon after the transition to delayed reinforcement were accompanied by decreases in eating times and alterations in interresponse-time distributions. As response rates decreased and became stable, eating times increased and their variability decreased. These findings support an interpretation of the effects of delayed reinforcement that emphasizes the importance of hopper-observing behavior.     

Responding under basic schedules of reinforcement in the crow.

Conditioned 5 crows to key-peck for food reinforcement using standard operant-conditioning apparatus and procedures. Responding under fixed-ratio, variable-interval, variable-ratio, and fixed-interval schedules of reinforcement was successfully maintained for each S with substantial schedule requirements. Terminal patterns of response under each of the schedules were similar to those displayed by other species, with the exception that crows paused longer after reinforcement, and responded more slowly under fixed-interval schedules, than pigeons usually do. Functional relationships between measures of performance and schedule requirements were quite consistent with reports on other species. (22 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Response-independent events in the behavior stream

The metaphor of the behavior stream provides a framework for studying the effects of response-independent food presentations intruded into an environment in which operant responding of pigeons was maintained by variable-interval schedules. In the first two experiments, response rates were reduced when response-independent food was intruded during the variable-interval schedule according to a concomitantly present fixed-time schedule. These reductions were not always an orderly function of the percentage of response-dependent food. Negatively accelerated patterns of key pecking across the fixed-time period occurred in Experiment 1 under the concomitant fixed-time variable-interval schedules. In Experiment 2, positively and negatively accelerated and linear response patterns occurred even though the schedules were similar to those used in Experiment 1. The variable findings in the first two experiments led to three subsequent experiments that were designed to further illuminate the controlling variables of the effects of intruded response-independent events. When the fixed and variable schedules were correlated with distinct operanda by employing a concurrent fixed-interval variable-interval schedule (Experiment 3) or with distinct discriminative stimuli (Experiments 4 and 5), negatively accelerated response patterns were obtained. Even in these latter cases, however, the response patterns were a joint function of the physical separation of the two schedules and the ratio of fixed-time or fixed-interval to variable-interval schedule food presentations. The results of the five experiments are discussed in terms of the contributions of both reinforcement variables and discriminative stimuli in determining the effects of intruding response-independent food into a stream of operant behavior.     

Discriminative stimulus effects on enadoline in pigeons

The discriminative stimulus effects of enadoline were characterized in pigeons responding under a fixed-ratio 20 schedule of food presentation and discriminating between intramuscular injections of the kappa opioid agonist enadoline and saline. Cumulative doses of enadoline dose-dependently increased drug-key responding with the training dose of enadoline (0.178 mg/kg) producing > or = 90% drug key responding (% DR). In time course studies, doses of enadoline larger than 0.32 mg/kg produced > or = 90% DR for more than 40 min. Naltrexone antagonized both the discriminative stimulus and the rate-decreasing effects of enadoline (pA2 = 6.79 and 6.73, respectively); in some pigeons, naltrexone produced an unsurmountable antagonism of the enadoline discriminative stimulus. Substitution tests using the kappa agonists U-50,488, spiradoline, U-69,593 and ethylketocyclazocine resulted in > or = 90% DR in most, but not all, pigeons; at larger doses, all compounds markedly decreased response rates. Up to rate-decreasing doses, nalorphine, dynorphin A(1-13) amide (DYN), nalbuphine, butorphanol, morphine and ketamine failed to occasion > or = 90% DR; nalbuphine, nalorphine, butorphanol, but not DYN, antagonized the discriminative stimulus and the rate-decreasing effects of enadoline. This study established stimulus control with enadoline in pigeons and results from substitution studies in these pigeons support the view that the enadoline discriminative stimulus is mediated by kappa opioid receptors; these results further demonstrate that nalbuphine and butorphanol have kappa antagonist actions in pigeons. The negative results obtained with DYN are in contrast to previous demonstrations of kappa agonist effects for DYN and might provide support for the hypothesized importance of nonopioid systems in the effects of this peptide.     

Molecular mechanisms resulting in pathogenic anti-mouse erythrocyte antibodies in New Zealand black mice

A procedure was developed with pigeons to extend the experimental analysis of punished behavior and the effects of anxiolytic drugs. Under this procedure the completion of a fixed-ratio requirement on a changeover key switched between two variable-interval schedules of reinforcement that were programmed on a second response key. Under one schedule, correlated with a green keylight, key pecks produced only food; under the second schedule, correlated with a red keylight, key pecks produced both food and electric shock. Pigeons were switched into the component with shock if they did not enter that component within 5 min. Parameter values of the variable-interval schedules were manipulated systematically and the effects of two clinically active anxiolytic drugs, buspirone and chlordiazepoxide, were examined. Responding was suppressed during the component with shock (punishment) and, under non-drug conditions, pigeons infrequently switched into the punishment component; changeover responses occurred rapidly when switched into the punishment component. Both buspirone (0.1-3.0 mg/kg) and chlordiazepoxide (3.0-30 mg/kg) increased punished responding at doses that had little effect on unpunished responding; d-amphetamine (0.3-5.6 mg/kg), which was studied only under one parameter of the variable-interval schedule, produced greater decreases in rates of punished responding than in unpunished responding.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effects of carbon disulfide and FLA-63 on operant behavior in pigeons

Carbon disulfide (CS2) and FLA-63 [bis(4-methyl-1-homopiperazinylthiocarbonyl)disulfide] were studied in pigeons working on a differential-reinforcement-of low-rates or a multiple fixed-interval fixed-ratio schedule of food reinforcement. Response rate on both schedules decreased after 8-hour exposures to CS2 (2 mg/1) of administration of FLA-63 (40 and 80 mg/kg). The effects of two successive 8-hour exposures to CS2 were cumulative and ten successive 4-hour exposures produced changes in differential-reinforcement-of-low-rates performance resembling those following acute exposure. Fixed-interval performance was disrupted by exposures to CS2 and doses of FLA-63 that left fixed-ratio performance intact.     

Punishment alters the discriminative stimulus effects of midazolam.

Experiment 1 examined the effects of punishment on the discriminative stimulus (DS) effects of midazolam (M) and pentobarbital (P) in 3 pigeons. Sessions began with a fixed-interval (Fl) 3-min schedule of food reinforcement. After 40 min, either saline (S) or 0.56 mg/kg of M was injected. A drug-discrimination (DD) component began 10 min later. Pecking the left key produced grain after S injections, whereas pecking the right key produced grain after M. Dose-response curves for M and P were obtained under these conditions and also when every 30th peck during the Fl was punished by shock. The introduction of punishment increased sensitivity to the DS effects of M and P. Experiment 2 examined whether a punishment history increases sensitivity to the DS effects of M. After DD training and testing, pecking was punished for 10 sessions. This history shifted the M dose-response curve to the left for 3 of 4 pigeons. These results emphasize the contribution of behavioral variables to the DS effects of drugs. Environmental variables appear to play a prominent role in guiding sensitivity to the subjective effects of drugs. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Fluvoxamine effects on concurrent ethanol- and food-maintained behaviors.

In previous studies, the selective serotonin reuptake inhibitor fluvoxamine preferentially reduced responding for ethanol compared with responding for food under conditions in which each was available alone in separate groups or in the same subjects under a multiple schedule in which baseline response rates were matched. The impact of providing concurrent access to food on pharmacological effects on ethanol self-administration remains largely unexplored. In this study, acute doses of fluvoxamine (3.0-17.8 mg/kg) were administered 30 min before the experimental session to Lewis rats responding under a concurrent fixed-ratio, fixed-ratio schedule of ethanol and food presentation. Ratios for food were adjusted for each subject to provide matched rates of food and ethanol reinforcement across the 30-min session. Although the number of ethanol and food deliveries did not significantly differ under baseline conditions, response rates did differ. Following fluvoxamine administration, responding for food was decreased more than responding for ethanol. This differential effect did not appear to be related to response rate or fixed-ratio size. Thus, the selectivity of fluvoxamine on ethanol- versus food-maintained responding depends on the context in which the behavior occurs. Such results may help explain inconsistencies between preclinical results and those in humans, and could provide insight into the behavioral determinants of pharmacological effects on ethanol self-administration. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Behavior maintained by alfentanil or nalbuphine in rhesus monkeys: Fixed-ratio and time-out changes to establish demand curves and relative reinforcing effectiveness.

A fixed-ratio, time-out schedule of intravenous alfentanil or nalbuphine delivery was used to maintain responding in rhesus monkeys (Afacaca mlulatta) during twice-daily 2-hr sessions of unrestricted access. Four doses of each drug were tested under 10 response fixed-ratio and lO-s time-out baseline conditions. Either the fixed ratio or the time-out was periodically increased during single sessions. Alfentanil maintained higher response rates than nalbuphine under conditions in which response rates were limited by the size of the fixed ratio rather than by unconditioned effects. This indicates that alfentanil is a more effective reinforcer than nalbuphine, which is predicted on the basis of the greater intrinsic efficacy of alfentanil relative to nalbuphine at the mu opioid receptor. Unit price analysis of these data demonstrated that a single demand function could be drawn for each drug, indicating that for these opioids in this situation, increasing the dose per injection was equivalent to decreasing the fixed ratio. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The effects of levo-alpha-acetylmethadol and its metabolites on schedule-controlled behavior in the pigeon

The effects of orally administered levo-alpha-acetylmethadol (LAAM) on the schedule-controlled behavior of the pigeon were compared with those of methadone. Both LAAM and methadone decreased rates of responding under a multiple fixed-interval 5-min, fixed-ratio 30-response schedule of food presentation. Although LAAM had a longer duration of action than methadone, both drugs were similar in the onset and potency of their behavioral effects. The chronic administration of either LAAM or methadone produced tolerance to the respective behavioral effects of each drug. In one set of experiments, the behavioral effects of intramuscularly administered LAAM were compared with those of its active metabolites, levo-alpha-noracetylmethadol and levo-alpha-dinoracetylmethadol. All three drugs decreased rates of responding under both components of the multiple schedule. The onset of these rate-decreasing effects was rapid and the order of potency for the production of these rate-decreases was levo-alpha-noracetylmethadol greater than levo-alpha-dinoracetylmethadol greater than or equal to LAAM. The rate-decreasing effects of LAAM and its metabolites were typical narcotic effects as defined by their reversal by naloxone.     

Effects of d-amphetamine on responding of squirrel monkeys maintained under second-order schedules of food presentation, electric shock presentation or stimulus-shock termination

The effects of d-amphetamine (0.01-5.6 mg/kg i.m.) were studied on lever pressing of squirrel monkeys maintained under various second-order schedules by a visual stimulus (S) that, with separate monkeys, was occasionally paired with the presentation of either food, electric shock or with the termination of a stimulus in the presence of which shocks occurred. Under one condition, the first response after 5 min produced a 3-sec stimulus change and the fourth stimulus change was followed immediately by food delivery, electric shock presentation or by the termination of a stimulus in the presence of which shocks occurred [fixed-ratio (FR); fixed-interval (FI) [FR 4 (FI 5-min:S)]. The effects of d-amphetamine were also studied under the food- and shock-presentation schedules when food or shock occurred only once, at the end of each session, after completion of 53n 3-min fixed-intervals all of which ended with a brief stimulus change [FR 10 (FI 3-min : S)]. Under a third condition, each thirtieth response produced the 3-sec brief stimulus (FR 30 : S) and the first FR 30 completed after 5 min elapsed produced the stimulus followed by food or, with separate monkeys, electric shock [FI 5-min (FR 30:S)]. Low to intermediate doses of d-amphetamine (0.03-0.3 mg/kg) generally increased and higher doses (0.56-5.6 mg/kg) decreased responding under all conditions. The effects of d-amphetamine on responding maintained by brief stimuli under different types of second-order schedules are generally similar, regardless of the type of reinforcing event or particular second-order schedule.     

d-Amphetamine, operant history, and variable-interval performance

The effects of d-amphetamine on the bar-pressing of rats maintained under a variable-interval schedule of water reinforcement were examined as a function of the operant history of the subjects. One group of rats initially received 51 sessions of exposure to a fixed-ratio 20 schedule, while a second group received equivalent exposure to an interresponse-time-greater-than-12-sec schedule. Mean group response rate when stable was over ten times as high under the fixed-ratio schedule as under the interresponse-time-greater-than-12-sec schedule. Response rates of the two groups largely converged across 47 sessions of exposure to a variable-interval 60-second schedule, at which time response rates for both groups appeared stable. Acute administration of d-amphetamine sulfate similary affected mean response rates of both groups: A 0.25 mg/kg dose did not obviously affect rate, while doses of 0.5, 1.0, and 2.0 mg/kg produced dose-dependent rate decreases. These results indicate that the efficacy of operant history as a determinant of drug effects may be limited to circumstances where current contingencies do not exercise powerful and direct control over behavior.     

Opioids and rate of positively reinforced behavior: II. Antagonism by β-funaltrexamine.

Lever pressing by rats (Rattus norvegicus) was maintained under a fixed-ratio 20 schedule of food presentation. Response rate-decreasing effects of the opioid compounds fentanyl, U50,488, butorphanol, and nalorphine were examined alone and in combination with the irreversible, μ-selective opioid antagonist β-funaltrexamine (β-FNA) antagonized the rate-decreasingly effects of both fentanyl and butorphanol. β-FNA was more potent and the duration of antagonism was greater, against butorphanol than against fentanyl. β-FNA also antagonized the effects of the higher nalorphine doses: however, lower doses of nalorphine, which were without effect alone, decreased response rates in the presence of β-FNA. The dose–effect curve for U50,488 was shifted leftward in the presence of β-FNA. These data suggest that, β-FNA may be useful in assessing μ-receptor activity related to the effects of opioids on rate of operant behavior and the efficacy with which opioids produce these effects. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Behavioral contrast in pigeons depends upon the operant.

Reinforced 3 male Carneaux pigeons for depressing a foot treadle according to multiple VI/VI schedules. After rates of responding stabilized, the schedule in 1 component was changed to extinction. This manipulation resulted in either no change or a decrease in rate of responding in the unchanged component. The Ss were then reinforced for key pecking under the same procedure. When key pecking was the operant, the experimental manipulation resulted in behavioral contrast. Results are discussed in terms of Pavlovian * Instrumental interactions. (17 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Sensitization to cocaine in pigeons: Interaction with an operant contingency.

A 2-part study with pigeons investigated the role of an explicit operant contingency in determining how cocaine interacts with locomotor activity. In Part 1, pigeons pecked on a fixed-ratio-20 schedule of food presentation. In Part 2, different pigeons were studied without opportunity to peck for food. After determination of cocaine's initial effects, pigeons were exposed to daily administrations of a locomotion-increasing dose of cocaine. Locomotor sensitization was evident in the pigeons of Part 2, and tolerance developed to cocaine's effects on key pecking in the pigeons of Part 1. Locomotor sensitization was generally not evident in the pigeons of Part 1. These results suggest that explicitly conditioned operant behavior may compete with behavior sensitized by prolonged exposure to cocaine. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Key-peck probability and topography in a concurrent variable-interval variable-interval schedule with food and water reinforcers

The relation between variables that modulate the probability and the topography of key pecks was examined using a concurrent variable-interval variable-interval schedule with food and water reinforcers. Measures of response probability (response rates, time allocation) and topography (peck duration, gape amplitude) were obtained in 5 water- and food-deprived pigeons. Key color signaled reinforcer type. During baseline, response rates and time allocations were greater to the food key than to the water key, and food-key pecks had larger gapes and shorter durations. Relative probability measures (for the food key) were increased by prewatering and decreased by prefeeding. Deprivation effects upon topography measures were apparent only when food- and water-key pecks were analyzed separately. Food-key gape amplitudes increased with prewatering and decreased with prefeeding. The clearest effect occurred with prewatering. There were no consistent effects upon water-key gapes. The key color-reinforcer relation was reversed for 3 pigeons to determine how response topography was modulated during the transition from food- to water-key pecks. Reacquisition was faster for the probability than for the topography measures. Analysis of gape-amplitude distributions during reversal indicated that response-form modulation proceeded through the generation of intermediate gape sizes.     

Effects of d-amphetamine and cocaine on strained ratio behavior in a repeated-acquisition task

Pigeons acquired a different four-response chain each session by responding sequentially on three keys in the presence of four colors. When the fixed-ratio requirement for food presentation was five completions of the chain, d-amphetamine and cocaine disrupted the behavior. As the dose of each drug was increased, the overall response rate decreased, the overall accuracy was impaired (i,e., percent errors increased), and there was less within-session error reduction (acquisition). In contrast, when the fixed-ratio requirement was either 20 or 50 completions of the chain, certain doses of both drugs produced large increases in the overall response rate by eliminating the extended pausing (ratio strain) that was characteristic of the control sessions. These rate-increasing effects were accompanied by error-decreasing effects, both during acquisition and after the response chain had been acquired. Taken together, the results show that the effects of d-amphetamine and cocaine on behavior in a repeated-acquisition task can be modulated by manipulating the value of the fixed-ratio schedule maintaining the behavior.     

Motivational influences underlying prolactin-induced feeding in doves (Streptopelia risoria).

Prolactin (Prl) increases food consumption in ring doves (Streptopelia risoria) and may promote the hyperphagia exhibited by parent doves when provisioning young. These experiments tested whether Prl also enhances appetitive aspects of feeding behavior. Prl elevated pecking rates in food-restricted doves on a variable-interval (VI) reinforcement schedule and supported continued responding when doves were returned to ad-lib feeding. Prl-treated doves learned the key-pecking response when food intake was clamped at ad-lib levels exhibited before Prl treatment but not when given free access to food. Median break points on a progressive ratio schedule were 2–3 times greater in food-restricted doves than Prl-treated, food-clamped doves even though response rates were similar on VI schedules. These results indicate that Prl enhances appetitive aspects of feeding, although food restriction at the level imposed in this study was more effective in this regard. (PsycINFO Database Record (c) 2010 APA, all rights reserved)