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R Liljequist

Publications and source records attributed to R Liljequist.

At least 19 recordsLinked to original sources
PubMed1997

Catechol O-methyltransferase inhibitor tolcapone has minor influence on performance in experimental memory models in rats.

Two catechol O-methyltransferase inhibitors, peripherally acting entacapone and also centrally acting tolcapone, were tested regarding their capacity to influence learning and memory in adult intact rats. Tolcapone was also studied in rats treated with scopolamine, in adult rats lesioned in the nuclei basalis magnocellularis, and in aged rats. Spatial working memory performance (radial-arm maze) of intact rats was facilitated following pretraining i.p. administration of tolcapone (10 mg/kg). Entacapone was ineffective at doses of 10 and 30 mg/kg. Senescent poor performers improved their accomplishment in the spatial memory task (linear-arm maze) under the influence of tolcapone. Scopolamine (1 mg/kg) impaired working memory performance. Bilateral lesions in the nucleus basalis magnocellularis reduced choline acetyltransferase activity in the frontal cortex by 26% and retarded the learning rate of spatial place task. Tolcapone was not able to counteract the performance deficits in these models. It is concluded that tolcapone can either slightly improve or impair the memory functions depending on task specific elements and performance factors.

Aging↗
PubMed1993

Subchronic MK-801 treatment to juvenile rats attenuates environmental effects on adult spatial learning.

Treatment with the non-competitive NMDA receptor blocker MK-801 (0.16 mg/kg), given to juvenile rats before and after the exposure to an enriched environment on alternate days for 4 weeks, attenuated the improvements in spatial learning and open field adaptation which resulted from such environmental stimulation. Drug treatment affected the consolidation of experiences as an injection given after exposure to the enriched environment was needed to demonstrate this effect. In addition, MK-801 administration diminished the adverse effect of stimulus deprivation-the slow learning rate normally seen in rats housed in impoverished environment. Radioligand binding studies showed that drug treatment decreased [3H]MK-801 binding sites in cortex. The learning, activity and receptor binding effects were measured 4 months from cessation of the drug treatment and environmental manipulation. The results support the role of NMDA receptors in mediating cognitive changes associated with environmental stimulation.

Animals↗
PubMed1993

Interaction of taurine and related compounds with GABAergic neurones in the nucleus raphe dorsalis.

The effects of GABAA (muscimol) and GABAB (baclofen) receptor agonists on spontaneous motor activity and food consumption of rats were compared to those produced by taurine and related compounds (3-aminopropanesulphonic acid, 5-aminovaleric acid, and guanidinoethanesulphonic acid). Local application of muscimol into the nucleus raphe dorsalis caused a dose-dependent increase in spontaneous motor activity. Muscimol-stimulated motor activity was blocked by picrotoxin. High doses relative to muscimol of 3-aminopropanesulphonic acid, guanidinoethanesulphonic acid, and 5-aminovaleric acid also attenuated the action of muscimol. Taurine by itself was ineffective on locomotion but enhanced the effect of a small dose of muscimol. Baclofen also stimulated activity but to a lesser extent than muscimol. Baclofen's stimulatory action on motor activity was partially blocked by 5-aminovaleric acid, whereas 3-aminopropanesulphonic acid was without effect. Muscimol and baclofen both increased food consumption of rats. Picrotoxin blocked this effect of muscimol, whereas the action of baclofen was blocked by 5-aminovaleric acid. Muscimol, taurine, and guanidinoethanesulphonic acid all reduced 5-hydroxytryptamine (5-HT) concentration in the hypothalamus. In radioligand binding studies, guanidinoethanesulphonic acid at micromolar concentrations displaced [3H]GABA from GABAA receptors. It is concluded that taurine may have a slight direct effect on GABA receptors but is more likely to act as an indirect neuromodulator of GABAergic neurotransmission in the brain.

Animals↗
PubMed1981

Codeine-induced memory changes: nature and relationship to opiate system.

Learning and recall processes were studied in three experiments with 33 subjects, 1 and 3 h after oral administration of codeine phosphate 25 mg, 50 mg and 100 mg. Recall was measured 3 and 24 h after drug administration. Nine subjects received naloxone i.m. with the 50 mg dose of codeine. Learning and memory were assessed by using associative, serial and concept learning tasks. Flicker fusion frequency was measured to assess the general vigilance level of the subjects. Learning performance in the serial learning task was improved 3 h after administration of codeine 100 mg. Recall in the serial learning task was also improved after codeine 25 mg, but only when the material was learnt after 1 hour and was recalled 24 h after drug intake. To demonstrate the enhanced recall both learning and recall had to take place under the same drug condition. The same test showed a tendency to enhanced recall after codeine 50 mg of material learnt 1 hour after drug intake and recalled 24 h later. This effect was counteracted by naloxone. The data are consistent with the hypothesis that codeine may exert its action via opiate receptors and that this system participates in memory functions.

Adult↗
PubMed1979

Acute effects of temazepam and nitrazepam on psychomotor skills and memory.

Twelve pretrained students ingested temazepam, nitrazepam, and placebo, each double blind at one-week intervals in randomized order. Reactive and co-ordinative skills and critical flicker fusion were measured before each drug intake and 1, 2, 3, 6 and 8 hours after it. Short-term memory and paired association learning were measured at 1, 3 and 8 hours. The psychomotor responses to drugs were modified by a sequence effect (not at zero tests) which effect varied depending on the drug and parameter. In multivariance analysis it was included to reveal drug effects. Nitrazepam 10 mg increased reaction and co-ordination errors and also impaired learning and memory. Temazepam 10 mg impaired co-ordinative skills; on a whole it differed from nitrazepam but hardly from placebo. Temazepam 20 mg impaired co-ordination, and learning and memory. Both temazepam 20 mg and nitrazepam were experienced sedative. All drug effects were clearest during the first 3 hours, nitrazepam also impaired learning at 8 hours. Temazepam 20 mg seems suitable as a hypnotic.

Adult↗
PubMed1979

Effects on learning and memory of 2-week treatments with chlordiazepoxide lactam, N-desmethyldiazepam, oxazepam and methyloxazepam, alone or in combination with alcohol.

A double-blind study with 40 healthy students was done in order to measure the effects of a 2-week treatment with chloridiazepoxide lactam (5 mg), nordiazepam (10 mg), oxazepam (15 mg) and methyloxazepam (20 mg) on immediate memory and associative learning. The drugs were administered t.i.d. and the tests were done after the very last capsule was given. It was ingested with a placebo drink and 0.5 g alcohol/kg body weight. Oxazepam and methyloxazepam alone behaved similar to the placebo. Immediate memory was significantly impaired following the treatment with nordiazepam, chlordiazepoxide lactam, alcohol, and after the simultaneous administration of nordiazepam and chlordiazepoxide lactam with alcohol. Chlordiazepoxide lactam was the only drug which alone impaired associative learning. Also alcohol alone, and all the drugs in combination with alcohol retarded learning acquisition.

Adult↗
PubMed1979

Effect of physostigmine and scopolamine on the memory functions of chess players.

Six young trained chess players received 10 consecutive tasks comprising problematic play position at chess. Each subject was tested four times with drug orders balanced across subjects. Compared with saline placebo, physostigmine (20 microgram/kg i.v.) in the presence of peripheral muscarinic blockade (methylscopolamine 6 microgram/kg i.v.) impaired the performance of good players, but the amount of correct solutions was increased when the initial performance level was low. Scopolamine (6 microgram/kg i.v.) impaired the performance of all subjects, and saline placebo proved inactive. The effect of scopolamine together with physostigmine was about the average of the separate effects of these drugs. The subjects talked less, when mildly sedated, and felt nauseated after the physostigmine treatment. Antimuscarinics with and without physostigmine caused cycloplegia in all subjects.

Adult↗
PubMed1978

Effect of diazepam and chlorpromazine on memory functions in man.

The effect of a single oral dose of diazepam 10 mg or chlorpromazine 25 mg on memory in man was examined in a double-blind study, each drug being crossed-over against placebo, with 20 subjects for each drug. Kahn's Test for Symbol Arrangement and a paired association-learning task were used for assessment of acquisition, storage and retrieval, and state-dependency effects. A flicker-fusion test, two coordination tests, and a choice reaction task were used to evaluate alertness in the subjects. Diazepam significantly impaired acquisition, but slightly facilitated recall. Reaction time was shortened after acute diazepam treatment and coordination was impaired after two weeks treatment with diazepam. Acute treatment with chlorpromazine did not change memory or psychomotor performance.

Adult↗
PubMed1978

Amitriptyline- and mianserin-induced changes in acquisition of paired-association learning-task.

1 The double-blind study on twenty healthy students was an attempt at assessing the effects of 2-week's treatment with amitriptyline (25 mg three times a day) and mianserin (10 mg three times a day), each alone or separatively inbibed with alcohol (0.5 g/kg) on the immediate memory and on the acquisition of a paired-association learning-task. 2 Amitriptyline impaired both the short-term memory-span and acquisition, and alcohol potentiated these effects. The action of mianserin did not deviate significantly from that of the placebo, and it also failed to interact with alcohol. 3 It is concluded that the decrement in learning capacity, that occurs after the 2-week's treatment with therapeutic doses of amitriptyline, reflects changes in both the intrinsic and the regulatory mechanisms of learning.

Adult↗
PubMed1978

Effects of amitriptyline and mianserin on psychomotor skills and memory in man.

1. Twenty volunteers were treated with amitriptyline 25 mg, mianserin 10 mg, and placebo, three times daily for 2 weeks each, in a double-blind cross-over study. Tests of psychomotor function and of learning and memory, were carried out after consumption of alcohol or a placebo drink at intervals during each treatment period. 2. Coordinative and reactive skills were affected by mianserin on the first day only, but by amitriptyline up to day 7 in most of the tests. Both drugs seemed to interact additively with alcohol. 3. Amitriptyline impaired short-term memory span and acquisition, and alcohol enhanced these effects. Mianserin did not affect learning and memory, and did not interact with alcohol in this respect. 4. The differing effects of amitripyline and mianserin are considered in relation to anticholinergic properties.

Adult↗
PubMed1977

Effect of alcohol and benzodiazepines on performance as related to personality characteristics. Personality characteristics among healthy "placebo reactors" and nonreactors.

For 2 weeks 40 volunteers received either 5 mg diazepam, t.i.d., or 10 mg chlordiazepoxide, t.i.d., and placebo. A choice reaction test, two coordination tests, and an attention test were administered to the subjects on the 14th day of each treatment. Thirty minutes before the tests, the subjects ingested either alcohol., 5g/kg or a placebo drink, incombination with the last capsule. After the test the subjects rated the quality of their treatment as placebo, tranquilizer, or stimulant. The psychological tests taken before the treatments were Eysenck's EPIC-NESI, Taylor's Manifest Anxiety Scale (MAS), and Cattell's 16 PF inventory. A multiple regression analysis was computed. Personality factor scores found to be associated with a strong effect of the benzodiazepines were 16 PF's A, C, L, N, and Q, and EPIC's E. The effect of alcohol was associated with a high score of 16 PFs B factor. Personality factors associated with "placebo reactors" and nonreactors were investigated, as well. Those subjects on placebo indicating their treatment to be active were classified as "placebo reactors". A discriminant analysis revealed that 16PF's O and I factors discriminated effectively "placebo reactors" from nonreactors, and EPIC's SE and 16 PF's L factor nonreactors from "reactors".

Adult↗
PubMed1977

Correlations between serum ami- and nortriptyline concentrations and psychomotor performance.

Correlations of serum nortriptyline (NT) and amitriptyline (AT) levels with psychomotor performance choice reaction performance, eye-hand coordination, and divided attention was studied in two experiments each with 20 healthy subjects. In the first experiment serum NT level was measured with an isotope derivative method after treatment for 14 days with NT. In the second trial plasma AT and NT concentrations were measured with gas-chromatography after treatment for 14 days with AT. No linear correlations between the levels of the antidepressants and performance variables were found. Low levels of NT (less than 50 ng/ml) tended to shorten reaction time, and intermediate levels (50--80 ng/ml) to prolong it, when compared with the reaction times during placebo. The correlation between serum NT levels and the increase of the tyramine dose in the tyramine pressor test was not significant. A new assay method for AT and NT is presented.

Adult↗