Biomedical subjects

G R Wenger

Publications and source records attributed to G R Wenger.

At least 19 recordsLinked to original sources

PubMed2003

Effects of drugs of abuse and signal predictability in two models of sustained attention in pigeons.

The acute effects of ethanol, pentobarbital, D-amphetamine and nicotine were determined in two animal models of attention. This study examined if changing the predictability of the stimulus presentation modifies drug effects under two attention tasks, in male White Carneau pigeons. The first task was a continuous-trial sustained attention task. For seven pigeons, the frequency of signal presentation was constant and predictable, once every 60 s [a fixed-interval 60 s (FI-60) signal presentation]. For seven additional pigeons, the frequency of signal presentation averaged once every 60 s, but the interval between presentations was random and variable [a variable-interval 60 s (VI-60) signal presentation]. Following ethanol (0.3-3 g/kg) and pentobarbital (0.3-13 mg/kg), decreases in p(hit) and large increases in p(false alarm) occurred at doses that did not impair response rates. Following D-amphetamine (0.03-5.6 mg/kg) and nicotine (0.03-3 mg/kg), a significant decrease in p(hit) and increase in p(miss) occurred at doses that did not impair response rates. The second task was a discrete-trial attention task, under which eight pigeons were presented a constant and predictable signal and eight were presented a random and unpredictable signal. Following ethanol (0.3-3 g/kg) and pentobarbital (0.3-13 mg/kg), drug effects on accuracy occurred at doses that suppressed responding. The schedule of signal presentation did not alter the effects of ethanol or pentobarbital. Following D-amphetamine (0.03-5.6 mg/kg) and nicotine (0.03-3 mg/kg), a significant decrease in p(hit) and increase in p(error of omission) occurred at doses that did not impair response latencies, but there were no differences between pigeons responding under the predictable (FI-60) or variable (VI-60) signal presentations. The observation of differential drug effects [e.g. p(false alarms)] on performance under the continuous-trial procedure supports the validity of the procedure for measuring drug effects on attention. However, changes in signal predictability had little effect on control or drug conditions under this continuous-trial sustained attention procedure.

Animals↗

PubMed2001

Effects of repeated exposure to JP-8 jet fuel vapor on learning of simple and difficult operant tasks by rats.

Groups of 16 Sprague-Dawley rats each were exposed by whole-body inhalation methods to JP-8 jet fuel at the highest vapor concentration without formation of aerosol (1,000 +/- 10% mg/m3); to 50% of this concentration (500 +/- 10% mg/m3); or to treated room air (70 +/- 81 L/min) for 6 h/d, 5 d/wk, for 6 wk (180 h). Although two subjects died of apparent kidney complications during the study, no other change in the health status of exposed rats was observed, including rate of weight gain. Following a 65-d period of rest, rats were evaluated for their capacity to learn and perform a series of operant tasks. These tasks ranged in difficulty from learning of a simple food-reinforced lever pressing response, to learning a task in which subjects were required to emit up to four-response chains of pressing three different levers (e.g., press levers C, R, L, then C). It was shown that repeated exposure to 1,000 mg/m3 JP-8 vapor induced significant deficits in acquisition or performance of moderately difficult or difficult tasks, but not simple learning tasks, as compared to those animals exposed to 500 mg/m3. Learning/performance of complex tasks by the 500-mg/m3 exposure group generally exceeded the performance of control animals, while learning by the 1,000-mg/m3 group was nearly always inferior to controls, indicating possible "neurobehavioral" hormesis. These findings appear consistent with some previously reported data for operant performance following acute exposure to certain hydrocarbon constituents of JP-8 (i.e., toluene, xylenes). There has, however, been little previously published research demonstrating long-term learning effects for repeated hydrocarbon fuel exposures. Examination of regional brain tissues from vapor-exposed rats indicated significant changes in levels of dopamine in the cerebral cortex and DOPAC in the brainstem, measured as long as 180 d postexposure, as compared to controls.

Administration, Inhalation↗

PubMed2001

Effects of drugs of abuse on response accuracy and bias under a delayed matching-to-sample procedure in squirrel monkeys.

The effects on memory of drugs of abuse from several pharmacological classes were examined in four adult male squirrel monkeys responding under a delayed matching-to-sample schedule of food presentation. Subjects were required to emit 20 responses on a sample key transilluminated by either a constant white or a flashing blue light. The twentieth response initiated a 3-second delay followed by presentation of two comparison stimuli. If a response was made to the key that matched the sample stimulus (correct match), a single food pellet (97 mg) was delivered. Pentobarbital (0.32-10 mg/kg), diazepam (0.1-5.6 mg/kg), phencyclidine (0.01-0.32 mg/kg) and cocaine (0.1-3.2 mg/kg) dose-dependently reduced accuracy of matching performance towards chance levels. Amphetamine (0.01-1.0 mg/kg) resulted in a small, but statistically significant, reduction in accuracy at a dose of 0.56 mg/kg, while 1.0 mg/kg completely suppressed responding. Analyses indicated that pentobarbital, diazepam and cocaine produced either position or color biases in responding, and in some cases these biases in responding were associated with decreases in accuracy. No such response biases were observed with phencyclidine or D-amphetamine. These results suggest that drug effects on working memory performance can, in some cases, be the result of non-mnemonic processes. Thus, they illustrate the importance of examining behavioral endpoints in addition to task accuracy when interpreting drug effects on working memory in laboratory animals.

Animals↗

PubMed2000

Pharmacophore/receptor models for GABA(A)/BzR subtypes (alpha1beta3gamma2, alpha5beta3gamma2, and alpha6beta3gamma2) via a comprehensive ligand-mapping approach.

Pharmacophore/receptor models for three recombinant GABA(A)/BzR subtypes (alpha1beta3gamma2, alpha5beta3gamma2, and alpha6beta3gamma2) have been established via an SAR ligand-mapping approach. This study was based on the affinities of 151 BzR ligands at five distinct (alpha1-3,5,6beta3gamma2) recombinant GABA(A)/BzR receptor subtypes from at least nine different structural families. Examination of the included volumes of the alpha1-, alpha5-, and alpha6-containing subtypes indicated that region L(2) for the alpha5-containing subtype appeared to be larger in size than the analogous region of the other receptor subtypes. Region L(Di), in contrast, appeared to be larger in the alpha1 subtype than in the other two subtypes. Moreover, region L(3) in the alpha6 subtype is either very small or nonexistent in this diazepam-insensitive subtype (see Figure 16 for details) as compared to the other subtypes. Use of the pharmacophore/receptor models for these subtypes has resulted in the design of novel BzR ligands (see 27) selective for the alpha5beta3gamma2 receptor subtype. alpha5-Selective ligand 27 when injected directly into the hippocampus did enhance memory in one paradigm (Bailey et al., unpublished observations); however, systemic administration of either 9 or 27 into animals did not provide an observable enhancement. This result is in complete agreement with the observation of Liu (1996). It has been shown (Liu, 1996; Wisden et al., 1992) that in the central nervous system of the rat (as well as monkeys and pigeons) there are several native subtypes of the GABA(A) receptor which exhibit different functions, regional distributions, and neuronal locations. Although 27 binds more potently at alpha5beta3gamma2 receptor subtypes and is clearly an inverse agonist (Liu et al., 1996; Liu, 1996), it is possible that this ligand acts as an agonist at one or more subtypes. Liu (1996) clearly showed that a number of imidazobenzodiazepines were negative modulators at one subtype and agonists at another. Therefore, selectivity for a particular subtype at this point is not sufficient to rule out some physiological effect at other GABA(A)/BzR subtypes. The inability of 27 to potentiate memory when given systemically is again in support of this hypothesis, especially since alpha1beta2gamma2 subtypes are distributed throughout the brain (Wisden et al., 1992). A drug delivered systemically is far more likely to interact with all subtypes than one delivered to a specific brain region. This observation (systemic vs intrahippocampal) provides further support for the design of more subtype-specific ligands at the BzR to accurately define their pharmacology, one key to the design of new drugs with fewer side effects.

Animals↗

PubMed2000

Effects of ethanol on working memory and attention in pigeons.

To determine whether the effects of ethanol on working memory are mediated by a secondary effect on attention, dose-response curves for ethanol were determined in eight pigeons trained under a titrating matching-to-sample (TMTS) procedure, in eight pigeons trained under a discrete-trial measure of attention, and in eight pigeons trained under a continuous-trial measure of attention. Ethanol decreased accuracy under the TMTS procedure following the three highest doses (1, 1.8, and 3 g/kg). Only the highest dose (3 mg/kg) decreased rates of responding. Attention, as measured under the discrete-trial procedure, was affected only by the two highest doses (1.8 and 3 g/kg). The 3-g/kg dose caused significant decreases in the probability of a hit and probability of a correct rejection, as well as significant increases in the probability of an error of omission and response latencies. Sensitivity to the signal decreased following 1.8 and 3 g/kg ethanol. Under the continuous-trial procedure, ethanol caused a peak in false alarms after the 1.8-g/kg dose, decreased the probability of a hit following the 1.8- and 3-g/kg doses, and increased probability of a miss at all doses. Sensitivity to the signal was not affected. A comparison of the dose-response curves for the TMTS procedure and the two measures of attention revealed that working memory (TMTS) was decreased by a lower dose than that affecting attention. This suggests that the effects of ethanol on working memory are not mediated by the subject's ability to pay attention to stimulus changes in the environment.

Algorithms↗

PubMed1998

Effects of drugs of abuse and scopolamine on memory in rats: delayed spatial alternation and matching to position.

Drugs of abuse produce amnestic effects in humans and laboratory animals in a variety of tasks. Generally, only a few compounds have been examined in any particular procedure. It was the goal of the present studies to examine drugs of abuse of different pharmacological classes in rats responding under two behavioral schedules historically employed as experimental models of memory: spatial alternation and matching to position. One group of rats responded under a single-response spatial-alternation baseline with a 10-s delay and another group responded under a matching-to-position baseline with delay values of 3, 10 and 30 s. Performance under the spatial-alternation baseline was characterized by low variability and >90% accuracy. Under the matching-to-position baseline, saline control percent accuracy was >95% at 3 s, >85% at 10 s and >70% at 30 s. Under spatial alternation cocaine, d-amphetamine, pentobarbital, diazepam, phencyclidine, scopolamine and methscopolamine produced significant (P<0.05) effects on accuracy, whereas only cocaine, d-amphetamine, pentobarbital and phencyclidine disrupted accuracy under the matching-to-position baseline. These results suggest that spatial alternation may be a more sensitive baseline for determining drug effects on working memory in the rat.

Animals↗

PubMed1997

Effects of drugs on response duration differentiation. V: differential effects under temporal response differentiation schedules.

The effects of methamphetamine, phencyclidine and delta9-tetrahydrocannabinol on responding under temporal response differentiation schedules were studied under three different time requirements. Under the schedules studied, Sprague-Dawley rats were required to make a continuous response for at least a minimum time duration, but not more than a maximum. Baseline performance under a temporal differentiation schedule usually produces a normal frequency distribution of response durations with the peak at or near the minimum duration required for delivery of the reinforcer. These frequencies were summed to calculate cumulative frequencies that were plotted as sigmoidal curves. Under the temporal differentiation 1-1.3 sec schedule, methamphetamine increased the frequency of short response durations at low doses, whereas high doses produced both long and short response durations, flattening the relative frequency distribution. Under the temporal differentiation 4-5.2 sec and 10-13 sec schedules, methamphetamine produced only short response durations, which shifted the relative frequency and cumulative frequency distribution of response durations leftward. delta9-Tetrahydrocannabinol had little effect under the temporal differentiation 1-1.3 sec and 4-5.2 sec schedules, but it greatly increased the relative frequency of short response durations under the 10-13 sec schedule. Phencyclidine produced a similar effect under all temporal differentiation schedules, increasing the relative frequency of short response durations. Thus the effect of drugs on timing behavior under these temporal differentiation schedules not only depended on the drug, but also depended on the dose and the time parameters of the schedule. These data suggest that drugs produce multiple effects on timing behaviors that depend on complex interactions among several factors.

Animals↗

PubMed1995

Linopirdine does not improve matching performance in the titrating matching-to-sample paradigm.

Linopirdine (DUP 996), a proposed cognitive enhancing agent, was studied in four squirrel monkeys (Saimiri sciureus) and six White Carneau pigeons responding under a titrating matching-to-sample paradigm (TMTS). Briefly, under this titration schedule, each trial began with the presentation of a sample stimulus on the center key of a three-key pigeon or squirrel monkey chamber. Completion of a fixed-ratio on the center key resulted in the termination of the stimulus presentation and the initiation of a delay period. The length of the delay changed as a function of the subject's performance. During the first five trials of each session, the delay was fixed at 3 s in length. On the sixth and all subsequent trials, the length of the delay increased, did not change, or decreased such that accuracy was maintained at approximately 80%. Following the delay, two of the three response keys were transilluminated with different colored lights. A single response on the key transilluminated with the same stimulus as the sample stimulus resulted in the presentation of food. A response on the key transilluminated with the stimulus that did not match the sample stimulus resulted in a timeout. Linopridine was administered in the pigeon (0.001-5.6 mg/kg) and squirrel monkey (0.01-1.0 mg/kg) 15 min before testing. Matching performance was not affected as measured by changes in mean delay values or percent accuracy even at doses that decreased rate of responding. These results suggest that the enhancement in cognitive function previously reported after administration of linopiridine may be limited to specific situations.

Animals↗

PubMed1994

Effects of drugs on response duration differentiation. III. Acute variation of reinforced duration.

Rats trained to hold a lever down for at least 1.0 s but less than 1.3 s could differentiate the reinforced response duration on about 50% of the trials. The response duration frequency distribution was a normal distribution with a peak near the minimum reinforced response duration. Dose-effect curves were determined for the effects of phencyclidine (PCP) and methamphetamine. Subsequently, rats continued to be trained for 3 days a week with responses between 1.0 and 1.3 s reinforced, but on days when injections were given either the maximum reinforced duration was increased to 2.3 s, or the minimum reinforced duration was lowered to 0.5. When the maximum duration was increased to 2.3 s, the percentage of reinforced responses increased to 60% and when the minimum reinforced duration was decreased to 0.5 s, the percentage of reinforced responses increased to 89%. Despite the increased percentage of reinforced responses when the time window was widened, the effects of PCP and methamphetamine were not changed. These data suggest that the effects of drugs on response duration differentiation are not greatly influenced by transient changes in reinforcement frequency.

Animals↗

PubMed1993

Titrating matching-to-sample performance in pigeons: effects of diazepam, morphine, and cholinergic agents.

Five adult, male White Carneau pigeons were trained to respond under a titrating matching-to-sample schedule of reinforcement. Under this titration schedule, each trial began with the presentation of a sample stimulus (red or green light) on the center key of a three-key pigeon chamber. Completion of 15 responses on the center key resulted in the termination of the stimulus presentation and the initiation of a delay period. The length of the delay changed as a function of the pigeon's performance. During the first five trials of each session, the delay was fixed at 3 s in length. On the sixth and all subsequent trials, the length of the delay was either increased, did not change, or decreased such that accuracy was maintained at approximately 80%. Following the delay, two of the three pigeon keys were transilluminated with different colored lights (red or green). A single response upon the key transilluminated with the same stimulus color as the sample stimulus resulted in the presentation of food. A response on the key transilluminated with the stimulus color that did not match the sample stimulus resulted in a time-out period. Using this procedure, the effects of two drugs of abuse, diazepam (0.03-3 mg/kg) and morphine (0.03-10 mg/kg), a muscarinic antagonist, scopolamine (0.003-0.3 mg/kg), the quaternary derivative of scopolamine, methylscopolamine (0.003-0.3 mg/kg), a cholinesterase inhibitor, physostigmine (0.003-0.1 mg/kg), and the quaternary derivative of physostigmine, neostigmine (0.003-0.1 mg/kg), were determined. Diazepam decreased matching accuracy such that a decrease in the mean delay value for the session was observed.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1993

Effects of drugs of abuse and cholinergic agents on delayed matching-to-sample responding in the squirrel monkey.

To study how drugs may disrupt short-term memory function, squirrel monkeys were trained to respond under a titrating delayed matching-to-sample schedule of reinforcement. Monkeys could respond on each of three keys in an operant chamber. At the start of each trial, the 30th response on the center key illuminated each of the side keys, one of which matched the stimulus presented on the center key (simultaneous matching). A response to the correct (matching) side key turned off all stimuli and initiated a delay, the length of which varied as a function of ongoing performance. After the delay, stimuli were randomly presented on two of the three keys. A response to the key which matched the color on the center key before the delay resulted in delivery of a food pellet (delayed matching). Incorrect simultaneous or delayed matching responses initiated a timeout. Under this procedure, diazepam and scopolamine decreased delayed matching accuracy at one or more doses that did not significantly decrease mean delay values, but only scopolamine decreased matching accuracy at a dose that did not significantly decrease response rates. Cocaine decreased mean delay values after the highest dose without affecting matching accuracy. Pentobarbital and methylscopolamine decreased matching accuracy and mean and maximum delay values after the highest doses. Nicotine and phencyclidine produced small decreases in delayed matching accuracy without affecting mean and maximum delay values. Caffeine, morphine, physostigmine and neostigmine did not alter matching performance even after doses that markedly decreased rates of responding.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1992

Effects of drugs of abuse on acquisition of behavioral chains in squirrel monkeys.

The acute effects of various drugs of abuse on the acquisition of chains of behavior were assessed in squirrel monkeys trained to respond on three keys for food. Each new session the monkeys acquired a different four-response chain by responding sequentially on three keys in the presence of four different stimuli. Incorrect responses inactivated the keys and darkened the chamber for 10 s (time-out). Dose-effect curves were obtained by administering the drugs intramuscularly before the session and recording their effects on the rate and accuracy of responding. Cocaine, d-amphetamine, and delta 9-tetrahydrocannabinol all decreased the accuracy and rate of responding within the dose range of 0.56-3 mg/kg. The highest dose of morphine tested (3 mg/kg) produced parallel decreases in the accuracy and rate of responding in some monkeys but had no effect at lower doses. These drugs decreased within-session accuracy though clearly acquisition did occur, but high doses of caffeine (30 and 56 mg/kg) prevented acquisition and recovery of performance and, furthermore, at 30 mg/kg these effects were observed in the absence of decreases in the rate of responding. The drugs of abuse tested all produced dose-related decreases in both the accuracy and rate of responding, and the decreases in accuracy were primarily observed only at doses that also decreased response rates. Therefore, based on these results from nonhuman primates each of these drugs has the potential to alter learning particularly when doses that disrupt other behaviors are administered.

Animals↗

PubMed1992

Titrating matching-to-sample performance: effects of drugs of abuse and intertrial interval.

Previous reports have shown that increasing the length of the intertrial interval (ITI) in a matching-to-sample schedule of reinforcement results in increased matching accuracy. This has traditionally been interpreted in the context of proactive inhibition, the disruption of memory for a stimulus as a consequence of events that occurred prior to the presentation of the stimulus. In an effort to more fully characterize a titrating matching-to-sample baseline, the effect of ITI ranging from 0-30 s was determined in pigeons trained to respond under the titrating matching-to-sample procedure. In addition, the effect of ITI length on the dose-response curve for pentobarbital, phencyclidine, D-amphetamine, and cocaine were determined. Surprisingly, performance under the titrating matching-to-sample was not altered as a function of ITI length, nor did the effects of the four drugs of abuse change as a function of ITI length. These results suggest that performance under the titrating matching-to-sample is under a different control than matching-to-sample using fixed delays.

Amphetamine↗

PubMed1990

Behavioral effects of cocaine and its interaction with d-amphetamine and morphine in rats.

Drugs of abuse are commonly co-abused, and frequently these combinations produce effects which cannot be predicted by studying the effects of the individual drugs. To investigate the behavioral interactions which occur following combinations of cocaine plus amphetamine or cocaine plus morphine, rats were trained to respond under a differential reinforcement of low rates (DRL) schedule (10-14 sec). Cocaine (0.1-10 mg/kg) and d-amphetamine (0.1-3 mg/kg) decreased the percentage of reinforced responses (efficiency) at doses which had no effect on overall rate of responding. Following moderate doses of either drug, the interresponse time (IRT) distribution showed an increase in the percentage of shorter (less than 10 sec) IRT's. Morphine (0.1-10 mg/kg) also decreased efficiency, but the decrease which occurred was only observed at doses which also decreased overall response rates. As might be expected, the IRT distribution for morphine showed a dose-related increase in the percentage of long IRT's (greater than 14 sec). When doses of morphine which had no significant effect when administered alone (1 or 3 mg/kg) were combined with cocaine, the cocaine dose-response curve for efficiency was shifted down and to the left and response rates were increased. Analysis of the IRT distribution showed that the combination of an ineffective dose of cocaine, 1 mg/kg, plus 3 mg/kg morphine produced a shift in the IRT distribution to the left (an increase in the percentage of short IRT's). When cocaine was combined with 0.3 mg/kg d-amphetamine, a dose which had no effect when given alone, no significant interactions were observed on efficiency or overall rate of responding.(ABSTRACT TRUNCATED AT 250 WORDS)

Amphetamines↗

PubMed1990

The acute effects of caffeine, cocaine and d-amphetamine on the repeated acquisition responding of pigeons.

The acute effects of caffeine, cocaine and d-amphetamine on the repeated acquisition of a four-response chain were investigated in pigeons. Subjects responded on three response keys under different predetermined sequences. Food was presented upon the completion of the four-response sequence under a fixed-ratio schedule. Incorrect responses resulted in a five-second timeout. No consistent increases in within session percent correct were observed following caffeine or d-amphetamine administration. However, cocaine (1.0 mg/kg) did produce consistent increases in within session percent correct. At higher doses of cocaine, d-amphetamine and caffeine the effects observed were similar in that there was a decrease in response rate and percent correct. The drugs did differ in the dose (potency) which decreased response rate and percent correct. Following all three drugs if percent correct was decreased there was a concurrent decrease in response rate.

Amphetamine↗

PubMed1990

The effects of cocaine in combination with other drugs of abuse on schedule-controlled behavior in the pigeon.

The present experiment sought to provide information regarding the consequences of combining cocaine with other drugs of abuse. The effects of cocaine alone and in combination with d-amphetamine, caffeine, morphine or delta-9-tetrahydrocannabinol were determined in five male white Carneaux pigeons responding under a multiple fixed-ratio 30, fixed-interval 600 schedule (mult FR FI). Drug interactions were studied by redetermining the cocaine dose-response curve in the presence of various fixed doses of the other drugs. Under the mult FR FI schedule, when cocaine (1 to 10 mg/kg) was combined with inactive doses of d-amphetamine (0.1, 0.3, 1.0, and 1.8 mg/kg), caffeine (10, 30, and 100 mg/kg), morphine (0.3, and 1.0 mg/kg), and delta-9-tetrahydrocannabinol (0.1 mg/kg), the FR and FI response rate dose-response curves were not shifted relative to the cocaine-alone curves. When cocaine was combined with an active dose of a drug which decreased response rate when given alone (0.3 mg/kg delta-9-tetrahydrocannabinol and 3 mg/kg morphine), the position of the response rate dose-response curves shifted compared to the cocaine-alone curves. The most frequent and consistent outcome of these interactions can be described as less than or approximately equal to an effect-additive interaction. Thus, these data indicate that the potential consequences of coabusing cocaine with the drugs tested in the present experiment can most often be predicted from the effects of each drug when taken alone.

Animals↗

PubMed1990

Disruption of performance under a titrating matching-to-sample schedule of reinforcement by drugs of abuse.

Five adult, male White Carneaux pigeons were trained to respond under a titrating delayed matching-to-sample schedule of reinforcement. Under this schedule, the length of the delay was changed as a function of the pigeons' performances in a manner that resulted in approximately 80% accuracy in matching performance. During the first five trials of each session, the delay value was fixed at either 3 sec or 30 sec (starting delay). On the 6th and all subsequent trials, the length of the delay value was increased by a fixed amount (the titration step), did not change or was decreased by an amount equal to the titration step. Initially, the starting delay and the titration step were set at 3 sec. These values were then systematically changed to a starting delay of 30 and a titration step of 3, and finally, a starting delay of 3 and a titration step of 1. Using this procedure, the effects of pentobarbital (0.3-10 mg/kg), cocaine (0.01-10 mg/kg), d-amphetamine (0.003-3 mg/kg) and phencyclidine (0.03-3 mg/kg) were determined under the different titration parameters. Pentobarbital was shown to decrease matching performance at doses (3, 5.6 and 10 mg/kg) that did not decrease response rates. Phencyclidine produced a similar effect at a dose of 1 mg/kg under two of the three phases of the experiment. No such specific effects were observed with cocaine or d-amphetamine. Thus, of the four drugs studied, pentobarbital showed the most pronounced effect on matching performance. Whether this represents merely a loss of stimulus control or a specific effect on memory is yet to be determined. In addition, the results of these experiments clearly show that when the delay value is allowed to change as a function of the pigeons' performance, pigeons are able to perform at or above 80% accuracy at longer delay values than those generally reported using fixed-delay values.

Animals↗

PubMed1989

The role of control activity levels in the reported strain differences to the behavioral effects of drugs in mice.

The effect of d-amphetamine (3-100 mumoles/kg), scopolamine (0.3-100 mumoles/kg) and morphine (3-1000 mumoles/kg) were studied on the spontaneous motor activity (SMA) of four strains of mice: CF-1, DBA/2, C57BL/6 and CD-1. All three drugs increased the SMA of the CF-1, C57BL/6, and CD-1 strains at low to moderate doses and decreased SMA at higher doses. In the DBA/2 strain, d-amphetamine and scopolamine increased SMA at low doses and decreased SMA at high doses; only decreases in SMA were observed with morphine. When the drug effect was expressed relative to control levels of SMA, large apparent strain differences were shown to exist for all three drugs. In general, these strain differences were shown to exist for all three drugs. However, the majority of these strain differences could be attributed to the large differences which existed in the control level of SMA among the four strains. One important exception to this statement was shown to exist. The DBA strain responded differently (only decreases in SMA were observed) to morphine than did the other three strains. This decrease was not related to the control SMA level and could not be antagonized by naloxone (3 mumoles/kg, IP).

Animals↗