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Biomedical subjects

J R Hyde

Publications and source records attributed to J R Hyde.

8 recordsLinked to original sources
PubMed1979

Piracetam impairs the overshadowing of background stimuli by an informative CS.

The effects of Piracetam (100 mg/kg) on passive avoidance learning was investigated in a situation in which rats received multiple conditioning trials. The test was based on the untrained preference of rats for a dark, rather than a brightly lit compartment. After the initial black-white preference was tested, rats were restricted to the black compartment for conditioning. Different groups received different percentages of tone-shock pairings. After the conditioning trials the black-white preference was again tested. The saline-injected rats showed overshadowing of the background stimulus by the tone, in the group that had received 100% tone-shock pairings; and an acquired aversion to the background stimuli in the group that had received 0% tone-shock pairings. In the rats injected with 100 mg/kg Piracetam associative strength was partitioned indiscriminately between the tone and the background stimuli, regardless of the tone-shock pairings that had been received during conditioning.

Animals↗
PubMed1979

A test of anxiety that distinguishes between the actions of benzodiazepines and those of other minor tranquilisers and of stimulants.

The effects of minor tranquilisers and of stimulant drugs were studied in the Social Interaction test of anxiety in which the illuminance and unfamiliarity of the test arena are manipulated. Acute administration of sodium phenobarbitone (25 mg/kg) was without effect. Acute administration of sodium phenobarbitone (35 mg/kg) and of meprobamate (60 mg/kg) produced sedation: both locomotor activity and social interaction were reduced. On the other hand, amphetamine sulphate (2 mg/kg) and caffeine citrate (20 mg/kg) reduced social interaction, but increased locomotor activity. Chronic administration dissociated the pattern of results produced by sodium phenobarbitone (35 mg/kg) from that produced by flurazepam (0.5 mg/kg). With chronic treatment (5 days) neither drug reduced motor activity, but whereas phenobarbitone increased social interaction regardless of the test illuminance and unfamiliarity, the increase produced by flurazepam was limited to the more stressful test conditions, i.e., when the arena was unfamiliar or brightly lit.

Amphetamine↗
PubMed1979

Ascending 5-HT pathways and behavioural habituation.

Microinjections of 5,7 -dihydroxytryptamine into both the dorsal and median raphe nuclei resulted in 70-85% depletions in striatal and hippocampal 5-HT concentrations but did not affect habituation of orienting in the lick-distraction test, habituation of activity in an open-field or habituation of exploration in the holeboard test. Lesioned animals were hypoactive in the latter two tests and defaecated more than control rats in the open-field suggesting an increase in emotionality or fear. Rats with selective 5,7 -dihydroxtryptamine lesions of either the dorsal or the median raphe nucleus also showed no impairment of habituation of orienting or exploration. However, median raphe lesioned animals were hyperactive at some stages of the holeboard test. In contrast to previous studies, the results suggest intact ascending 5-HT pathways are not necessary for behavioural habituation of orienting, activity or exploration. Rather, 5-HT neurones may be involved in modulation of activity or responsiveness to aversive environments.

Acoustic Stimulation↗
PubMed1979

Evidence that piracetam has an anxiolytic action.

In the social interaction test of anxiety Piracetam (100 mg/kg) had an anxiolytic profile very similar to that seen after 5 days of administration of chlordiazepoxide (5 mg/kg). Piracetam (50-300 mg/kg) produced no signs of sedation and it was therefore suggested that it might be a non-sedative anxiolytic drug. Piracetam (100 mg/kg) produced significantly higher cortical concentrations of 5-hydroxytryptamine and lower concentrations of 5-hydroxyindoleacetic acid, indicating a reduced 5-HT turnover. There were no drug-induced changes in noradrenaline or dopamine in any brain region, either with or without pretreatment with alpha-methylparatyrosine. The cortical concentrations of 7 amino acids were measured and were unchanged by treatment with Piracetam.

Amino Acids↗
PubMed1979

5,7-dihydroxytryptamine lesions of dorsal and median raphé nuclei and performance in the social interaction test of anxiety and in a home-cage aggression test.

Micro-injections of the neurotoxin 5,7-dihydroxytryptamine into the dorsal raphe nucleus produced a behavioural profile in the social interaction test of anxiety similar to that seen in rats treated chronically with benzodiazepines. Neurotoxin injections into the median raphé nucleus did not produce a profile significantly different from that of the controls. In the control rats and in the rats with lesions of the median raphé nucleus, ACTH1-24 (corticotrophin) significantly reduced active social interactions, whereas it was without effect on the rats with lesions of the dorsal raphé nucleus. In the home-cage intruder test, the median raphé-lesioned rats submitted less to the intruder and stood and jumped on him more often than did the controls. The dorsal raphé-lesioned rats showed significantly fewer interactions of all kinds, compared with control rats when an intruder was placed in their home cages.

5,7-Dihydroxytryptamine↗
PubMed1977

The effects of p-chlorophenylalanine and ethanolamine-O-sulphate in an animal test of anxiety.

p-Chlorophenylalanine, which produces a depletion of brain 5-HT concentration, had effects qualitatively similar to those previously found with chronic chlordiazepoxide and with acute ethanol in the social interaction test of anxiety. This result is compatible with the idea that a reduced turnover of 5-HT is important in anxiety reduction. On the same test, ethanolamine-O-sulphate, which raises brain gamma-aminobutyric acid, was without effect, suggesting raised concentrations of this acid are not essential for anxiety reduction.

Animals↗