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D M Grilly

Publications and source records attributed to D M Grilly.

At least 19 recordsLinked to original sources
PubMed1994

Differential effects of d-amphetamine on vigilance in younger and older male rats.

After training to comparable levels of performance on a two-choice, discrete-trial vigilance task, younger (9 mo) and older (26 mo) male F344xBN rats were tested after SC injections of d-amphetamine (0.125, 0.25, 0.50, and 1.0 mg/kg). Relative to their saline treatment performance levels, both groups exhibited decreases in choice latencies under the lower doses of amphetamine and an increase in food retrieval latencies after 1.0 mg/kg amphetamine. The percentage of correct responses in the older animals was lower than in the younger animals at all doses of amphetamine, and the groups differed significantly at the 0.25 and 0.50 mg/kg doses. There were no significant differences between the groups in either of the latency measures at any of the doses of amphetamine. These results suggest, as has been demonstrated with cocaine, that the alertness-altering properties of amphetamine are qualitatively different in older and younger adult organisms.

Aging↗
PubMed1992

Aging changes the effects of cocaine on vigilance task performance of rats.

To investigate age-related behavioral changes with the administration of cocaine, young (6-10 mo), middle-aged (12-18 mo), young-old (21-24 mo), and old (25-36 mo) rats that had been trained on a 2-choice, discrete trial vigilance task were tested under different doses of cocaine. The young and middle-aged rats exhibited significantly increased accuracy and decreased choice latencies following 2.5 mg/kg cocaine. A 15.0 mg/kg dose increased variability in these measures and increased food retrieval latencies. The young-old and old rats exhibited no significant changes in accuracy or choice latency to 1.25, 2.5, and 5.0 mg/kg cocaine; however, a dose of 15.0 mg/kg significantly reduced accuracy in both these groups and increased choice latencies in the old animals. Also, doses of 5.0 and 15.0 mg/kg tended to increase food retrieval latencies more in the two older groups than in the two younger groups. These results indicate that, rather than a simple increase or decrease in sensitivity, there is a qualitative change in cocaine's behavioral effects as rats age. These findings may reconcile long-standing discrepancies in the literature regarding age-related changes in the behavioral effects of amphetamine, with actions and effects very similar to those of cocaine.

Aging↗
PubMed1990

Cocaine and level of arousal: effects on vigilance task performance of rats.

Rats were food-reinforced for pressing one of two levers in an operant chamber, with the correct lever being indicated by the position of a briefly illuminated light. After stable accuracy levels were achieved, the rats were tested after an injection of either saline or cocaine (2.5 mg/kg) under two conditions. In the "low arousal" condition, animals were tested during the light phase of a 12-hr light-dark cycle and were fed approximately 5 hr prior to testing. In the "high arousal" condition, animals were tested during the dark phase after approximately 28-hr food deprivation. As expected, accuracy was higher and median choice and food retrieval latencies were shorter under the high arousal condition. Contrary to predictions, cocaine enhanced accuracy under both conditions. These results indicate that cocaine-enhanced performance in some tasks is not necessarily dependent on the animal performing at suboptimal arousal levels.

Animals↗
PubMed1990

Cocaine and vigilance task performance of rats: effects of delay of reinforcement.

In two experiments rats were food-reinforced for pressing one of two levers in an operant chamber, with the correct lever being indicated by the position of a briefly illuminated light. In Experiment 1 the levers were always in the chamber, whereas in Experiment 2 the levers were inserted into the chamber immediately after cue light termination and withdrawn immediately after a choice response. The rats were tested under four conditions: after an injection (SC) of saline or 2.5 mg/kg cocaine and with delay of reinforcement (DOR) of either 0 or 8 s. In both experiments, cocaine enhanced accuracy under the 0-s DOR condition. However, in neither experiment was there evidence of facilitation with cocaine under 8-s DOR, which by itself increased choice latencies and decreased accuracy when choice latencies exceeded 0.5 s. These results indicate that cocaine may only enhance performance in vigilance tasks under constrained conditions, e.g., those that require minimal levels of information processing.

Animals↗
PubMed1989

Effects of cocaine and d-amphetamine on sustained and selective attention in rats.

The effects of cocaine and d-amphetamine were compared in two attention-loading tasks. Cued by the position of a light, rats were food-reinforced for pressing one of two levers in a 2-choice, discrete-trial procedure. In the "sustained attention" task, the cue light was illuminated for a brief period (1.8 sec or less) at the beginning of each trial. In the "selective attention" task, the cue light remained on until a level press, while a blinking light over the incorrect lever served as a distractor. In the sustained attention task, low doses of d-amphetamine (0.25 mg/kg SC) and cocaine (2.5 mg/kg SC) enhanced accuracy; some doses of d-amphetamine (0.75 mg/kg SC) and cocaine (1.25 and 2.5 mg/kg SC) also reduced choice latencies. In the selective attention task, the lower doses of these drugs had no effect on accuracy, the highest dose of d-amphetamine (1.25 mg/kg SC) disrupted accuracy, and all doses of the drugs reduced choice latencies. The time to retrieve food was increased in a dose-dependent fashion by both drugs in both tasks. These results indicate that, other than differences in potency, cocaine and d-amphetamine induce similar behavioral effects in attention-loading tasks, with improvement or interference with performance dependent on the dose and the type of attention demanded of the task.

Animals↗
PubMed1988

Effects of naltrexone, and d-amphetamine, and their interaction on the stimulus control of choice behavior of rats.

The hypothesis that endogenous opioid peptides modulate attentional processes was tested. The effects of the opioid antagonist naltrexone (NALT), d-amphetamine (AMP), and their interaction were investigated in rats trained in a two-choice task in which the position of a short-duration light served as a cue for food-reinforced responses. NALT (0.25, 1.0, 5.0, and 10.0 mg/kg) produced no significant changes in performance (accuracy, choice latency, and food retrieval time). As predicted, AMP induced dose-dependent biphasic effects. Low doses of AMP (0.25 and 0.5 mg/kg) significantly enhanced accuracy, decreased choice latency, and lengthened food retrieval time; 1.25 mg/kg AMP disrupted accuracy, increased choice latency, and further lengthened food retrieval time. The combination of NALT (0.25, 1.0, and 10.0 mg/kg) and subthreshold doses of AMP (0.07 and 0.1 mg/kg) had no effect on performance except for an increase in food retrieval time with 10.0 mg/kg NALT, whereas the combination of NALT and moderate doses of AMP (0.5 and 1.0 mg/kg) disrupted accuracy, increased choice latencies, and lengthened food retrieval time. These results do not support the hypothesis that endogenous opioid peptides play a vital role in attentional processes or that opioid antagonists may be useful in the treatment of attentional deficit disorders.

Animals↗
PubMed1986

Acute morphine dependence: effects observed in shock and light discrimination tasks.

Alterations in shock discrimination accuracy in the rat, indicative of hyperalgesia, have been noted 1-3 days following a single injection of morphine. To establish the extent to which these "withdrawal-like" effects were specific to the shock discrimination paradigm, rats were trained in two separate discrimination tasks. The discriminative stimuli (SD,s) for correct lever presses were mild electric shocks of different intensities in one task and were short duration lights over the levers in the other. After achieving comparable accuracy levels in the two tasks, the animals were injected SC with 30 mg/kg morphine sulfate and performance levels assessed 1, 2, 3, and 7 days later. Shock discrimination accuracy was significantly enhanced on post-morphine day 2, while accuracy in the light position task was not significantly affected on any of the post-morphine test days. The results indicated that increased pain sensitivity, as well as other signs of dependence, can occur following acute exposure to morphine.

Animals↗
PubMed1986

Comparison of the effects of morphine and immobilization stress on discrimination performance of rats.

The effects of morphine and those of immobilization stress (IMS) on performance of rats in discrete-trial, two-choice discrimination tasks were compared. In Experiments 1 and 2, two shocks of different intensities were discriminative stimuli (SD) for choices in a T-maze. In Experiments 3 and 4, responses were right and left lever presses in an operant chamber, where correct responses were signaled by either shocks of different intensities (shock discrimination task) or by the position of a brief light flash (light discrimination task). In Experiment 1, both 70-min IMS and 5 mg/kg morphine induced greater disruptions in trials in which the higher shock was the SD, and there were no significant differences between treatments. However, in Experiment 2, only the effects of morphine were blocked by 10 mg/kg naltrexone. In Experiment 3, the effects of IMS and morphine were not selective with respect to SD shock level in the shock discrimination task, nor were they task (shock vs. light) selective. Also, the effect of morphine was significantly greater than the effect of IMS in both tasks. The results of Experiment 4 indicated that effects induced by actual alterations in the intensities of the SD shocks did not mimic those induced by either morphine or IMS but that abrupt decreases in the duration of the SD lights induced effects similar to those of morphine. These studies indicate that different mechanisms mediate the effects of IMS and morphine and much of their behavioral effects in shock discrimination tasks are due to dissociative processes rather than alterations in perceived shock intensity.

Animals↗
PubMed1984

How do tranquilizing agents selectively inhibit conditioned avoidance responding?

A number of tranquilizing agents have been shown to inhibit conditioned avoidance responses (CAR) at doses that do not interfere with escape responses (ER). To test the hypothesis that this selective action may be due to differential response strengths of the two responses, rats were trained to press retractable levers in an operant chamber either to avoid a 0.5 mA shock during a 5.0-s warning period or to escape from a low-intensity shock within 5.0 s. The intensity of the latter shock was adjusted for each animal so that CAR and ER were comparable in terms of probability of occurrence and latency. While doses of chlorpromazine, clonidine, diazepam, and morphine that reduced CAR by 30%-50% did not significantly affect high-shock ER, i.e., ER on CAR trials where no CAR occurred, they interfered with low-shock ER to the same degree as CAR. These and other results suggest that the selective blockade of the CAR by these drugs in the CAR paradigm is primarily due to differential strengths of the CAR and ER. They also support studies concluding that tranquilizing drugs reduce avoidance because of a deficit in the ability to initiate motor responses, rather than interfering with associative processes or reducing situation-induced emotional reactions. However, the finding of a small differential effect, at least with chlorpromazine, on CAR and low-shock ER across trials within sessions indicated that different mechanisms may be involved in the suppression of these two responses.

Animals↗
PubMed1982

Effects of immobilization stress on shock discrimination performance in rats.

It has been suggested that acute stress induces analgesia in rats and mice. However, stress can have a myriad of debilitating effects on organisms, and it is not clear whether stress decreases the perceived intensity of the painful stimulus (i.e., a change in sensitivity) or decreases the willingness or ability of the organism to carry out the appropriate bodily movement (i.e., a change in responsivity). Since traditional animal analgesia tests confound sensitivity with responsivity, we assessed the effects of immobilization stress on rats trained on a two-choice, two-shock discrimination task, in which the dependent measures are presumably less reflective of alterations in pain responsivity. Immobilization stress significantly disrupted shock discrimination performance, with the disruption occurring primarily in choice performance signalled by the higher intensity shock discriminative stimulus. These effects completely dissipated with successive daily exposures to stress. The data suggest that immobilization stress has a specific effect on pain sensitivity which is separate from its possible effects on pain responsivity.

Animals↗
PubMed1981

Morphine dependence in rats assessed in a shock discrimination task.

The effects of chronic morphine sulfate (5 mg/kg/day for 14 days) on shock discrimination performance of rats was assessed in Experiment 1. Significant tolerance developed to the disruptive effects of morphine on performance. A significant increase in discrimination performance was found 48 h after the last injection in tests conducted without the injection environment cues present. Ten days after the chronic drug regimen, tests conducted 30 min after exposure to the injection-environment cues revealed no differences between animals previously administered morphine and control animals administered saline. In Experiment II, shock discrimination performance was assessed in a separate group of rats after exposure to a single injection of morphine sulfate (30 mg/kg), which eliminated associative processes, e.g., Pavlovian or instrumental conditioning, as factors in the subsequent behavioral tests for hyperalgesia. Significant changes in discrimination performance (primarily enhanced percent correct to the high shock stimulus) indicative of increased pain sensitivity were obtained in tests conducted 1, 2, and 3, but not 9 days after the injection. These experiments indicate that increased pain sensitivity, as opposed to hyperresponsivity operationally measured in traditional analgesia tests (e.g., hot plate, jump-flinch, and tail flick), is a component of morphine withdrawal of a nonassociative origin.

Animals↗
PubMed1980

Effects of morphine, d-amphetamine, and pentobarbital on shock and light discrimination performance in rats.

The effects of 2 and 4 mg/kg morphine sulfate, 0.5 and 1 mg/kg d-amphetamine sulfate, and 6 and 12 mg/kg pentobaribital sodium were tested in rats in two different discrete-trial two-choice discrimination tasks. The discriminative stimuli for one task were high and low intensity shocks. In the other, correct choices were signaled by the position of a brief light flash. Morphine (4 mg/kg) significantly disrupted performance of both tasks, with more reliable disturbance occurring in the shock discrimination animals. Pentobarbital (12 mg/kg), while exerting noticeable effects on gross motor behavior, had little effect on discrimination performance; d-amphetamine (1 mg/kg) was disruptive of discrimination performance in only some animals. The results indicate that much of the effect of relatively low doses of morphine on the shock discrimination performance of rats may be due not to its putative specific antinociceptive properties, but to alterations in conceptual-judgmental processes or decreases in motivation (e.g., hunger) unrelated to pain.

Animals↗
PubMed1975

Effects of prior experience on differential learning under amphetamine.

Differential learning of operant behavior under non-drug and amphetamine states was explained with a "drug-behavior-reinforcement interaction" process. When a drug affects the relationship between ongoing behavior and existing reinforcement contingencies, the sets of behavioral patterns subjected to the process of reinforcement or non-reinforcement under a drug may differ from the patterns under non-drug conditions. If, following sufficient training, the drug conditions are then changed, persistence of these behavioral patterns may result in a difference from those patterns produced if acquisition occurs solely under non-drug conditions. To investigate this process, groups of rats were given varying amounts of non-drug acquisition training on a response-duration differentiation task before being given extended training under 0.75 mg/kg d-amphetamine. All groups were then tested under non-drug conditions. Amphetamine significantly enhanced performance, and this enhancement transferred to subsequent non-drug conditions. However, if non-drug training occurred before drug training, this enhancement was greatly attenuated. Furthermore, only those behavioral components under which amphetamine led to an increase in reinforcement rate showed enhancement in the non-drug state. The results, which supported the present position, were discussed in relation to a "stimulus generalization decrement" explanation of differential learning under amphetamine.

Animals↗