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R M Wylie

Publications and source records attributed to R M Wylie.

15 recordsLinked to original sources
PubMed1998

Effects of the serotonin agonists 8-OH-DPAT, buspirone, and DOI on water maze performance.

We have previously reported that the serotonin 5-HT1A agonist 8-OH-DPAT and the 5-HT2c agonist TFMPP impair performance on a water maze. In the present report we extended those studies by examining a second 5-HT1A agonist, buspirone, to see whether its effects paralleled those of 8-OH-DPAT, and by testing the effects of the 5-HT2 agonist DOI. Unlike the open pool Morris water maze, the maze used in these experiments has alleys and doorways. The maze can be easily reconfigured to present rats with both previously learned or new maze challenges. Performance is assessed by time to reach the maze exit platform and the number of wrong doorways entered (errors). At doses that did not affect performance in a previously learned maze, the 5-HT1A agonists 8-OH-DPAT (0.1 mg/kg) and buspirone (1 mg/kg) slowed acquisition of a new maze configuration as measured by both swim time to the exit platform and errors committed. A higher dose of buspirone (10 mg/kg) completely blocked acquisition of a novel maze. In contrast. DOI slowed performance as assessed by swim time on both a well-learned maze as well as acquisition of a new maze, but did not affect error rate on either task, suggesting that this 5-HT2 agonist impaired performance by depressing motor activity. These experiments demonstrate that serotonin agonists, especially the 5-HT1A subtype, can impair learning.

8-Hydroxy-2-(di-n-propylamino)tetralin↗
PubMed1996

Effects of triazolam and diazepam on learning and memory as assessed using a water maze.

One of the reported adverse side effects of the frequently prescribed benzodiazepines diazepam (Valium) and triazolam (Halcion) is an impairment of anterograde memory in humans. The experiments described in this article compared the effects of triazolam and diazepam on performance in a water maze task that is sensitive to drugs that affect learning and memory. The water maze utilized is a traditional type of maze with alleyways and door choices, unlike the Morris open water maze. Time required to find an out-of-the-water platform and errors committed during the swim are used as performance measures. Rats were tested on a previously learned maze configuration and on the acquisition of new maze configurations. Neither diazepam (0.25, 1.0, or 2.0 mg/kg) nor triazolam (0.05, 0.2, or 0.3 mg/kg) injected 30 min prior to testing on the previously learned maze affected swim time or errors committed. Administration of diazepam (0.5, 1.0, or 2.0 mg/kg, IP) prior to daily training on three different new maze configurations did not affect swim time, but did increase swim errors. Triazolam administered at 0.1, 0.2, or 0.3 mg/kg markedly impaired performance as assessed by either swim time or errors. There were no differences in performance of rats previously treated with triazolam, diazepam, or vehicle in learning another new maze after drug treatment was terminated. These data demonstrate that both diazepam and triazolam affect acquisition but not recall of maze configurations and support similar conclusions reached using other types of tasks in humans and animals.

Animals↗
PubMed1989

Performance of a weight-lifting task by normal and deafferented monkeys.

The role of topographic information from a moving limb in controlling the trajectory of the limb was explored by comparing the ability of 3 normal and 2 unilaterally deafferented monkeys to generate criterion elbow flexions when opposed by different weights. When lifting initially unknown weights, both groups of monkeys reached maximum positions that were inversely related to load. The performance of the deafferented monkeys approached that of the normal monkeys on these first lifts of initially unknown weights. The preceding load had a greater effect on the initial lifts of the deafferented monkeys than on those of the normal monkeys. When allowed to repeatedly lift the same weight, both groups obtained a high density of reinforcement, but the responses of the deafferented monkeys were more dependent on the weight. The results are consistent with the hypothesis that the mechanical properties of muscle make an important contribution to compensation.

Afferent Pathways↗
PubMed1981

Weight-lifting by normal and deafferented monkeys: evidence for compensatory changes in ongoing movements.

When trained in a weight-lifting paradigm, both normal and deafferented monkeys achieved high reinforcement densities at all test weights employed. Recordings of acceleration on the first lift of an unknown weight reveal that at some delay after the start of movement deafferented monkeys can alter the subsequent trajectory by a sudden change in applied torque. Comparison with normal animals indicates that short latency feedback pathways in normal animals contribute to the smoothness of movements made in the face of unknown external loads.

Afferent Pathways↗
PubMed1970

A short-latency labyrinthine input to the vestibular nuclei in the pigeon.

Electrical stimulation of the pigeon labyrinth evokes responses in many second-order vestibular neurons with a latency shorter than the monosynaptic delay. These early responses are probably due to electrically mediated synaptic transmission, or perhaps to antidromic invasion of cells supplying efferent fibers to the labyrinth. In either case the results demonstrate a difference between cat and pigeon with respect to connections between labyrinth and vestibular nuclei.

Animals↗