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Biomedical subjects

T Rammsayer

Publications and source records attributed to T Rammsayer.

11 recordsLinked to original sources
PubMed1990

Personality related differences in response to 5-HT uptake inhibition.

Conflicting results on clinical effects of serotonergic drugs gave rise to this investigation on the relationship between depression-related personality factors and effects of the 5-HT uptake inhibitor fluoxetine on psychomotor functions and emotional states. In a double-blind, balanced, crossover design, 24 healthy male subjects divided according to scales of "Experiencing of Stress" and "Neuroticism," were tested with a single dose of 60 mg fluoxetine or placebo. Reaction time and feelings of activation and energy of highly neurotic or stressed subjects were deteriorated by fluoxetine while emotionally stable subjects were improved by the drug. The findings were interpreted in terms of personality related differences in 5-HT neurotransmission and receptor sensitivity.

Adult↗
PubMed1990

Temporal discrimination in schizophrenic and affective disorders: evidence for a dopamine-dependent internal clock.

Performance in temporal discrimination of time intervals in the range of milliseconds was compared in 80 healthy subjects, 27 patients with schizophrenic disorders, 33 patients with major depression, 21 patients with dysthymic disorders. For schizophrenic patients as well as for patients with major depression, pronounced deficits in duration discrimination could be demonstrated as compared to the healthy control group (p less than .01). Patients with dysthymic disorders and schizophrenic patients differed significantly from the melancholic group (p less than .01 and p less than .05, respectively). The results are discussed on the basis of the assumption of an internal clock, implying that the clock rate is highest and therefore temporal resolution is best with healthy subjects. With psychiatric patients performance in temporal discrimination was impaired to a slowing down in clock rate and thus decreased temporal resolution. There is strong evidence that changes in clock rate depend on the effective level of dopamine. This leads to the conclusion that temporal discrimination thresholds may be seen as an indicator for deviations from the optimal level of dopaminergic activity in psychiatric patients. In addition, possible effects due to age and medication are discussed.

Analysis of Variance↗
PubMed1990

[Time order error and position effect of a standardized stimulus in discrimination of short time duration].

In comparison judgments of two successively presented time intervals ranging from 30 to 70 msec a time-order error (TOE) as well as a systematic effect depending on the constant position error (CPE) were demonstrated. The effects proved to be independent. Contrary to Vierordt's law, a negative TOE was found. When presenting the standard interval first, an increased hit rate resulting in a positive CPE was established. Furthermore, a test statistic is introduced that allows analysis of experiments utilizing all available information of a subject's psychometric function.

Adult↗
PubMed1989

Dopaminergic and serotoninergic influence on duration discrimination and vigilance.

There is some evidence from animal studies suggesting that dopamine (DA) agonists speed up a hypothesised internal clock, whereas DA antagonists such as haloperidol slow down the clock rate. Furthermore, clinical studies on haloperidol have reported significant deficits in duration discrimination performance (DD). Two double-blind balanced crossover studies with 24 healthy male volunteers each were designed to answer the following questions: 1. Do the DA agonists L-dopa and the DA antagonist haloperidol induce changes in DD? 2. Do the 5-HT uptake inhibitor fluoxetine and the 5-HT receptor antagonist ritanserin induce changes in DD? 3. Can any relationship be demonstrated between changes in DD and changes in vigilance? Haloperidol produced a marked decrease in DD, whereas for the DA agonist no changes could be demonstrated. Performance in DD was slightly improved by the 5-HT agonist and the 5-HT antagonist. Both dopaminergic and serotoninergic changes in DD seemed to be independent of the level of vigilance.

Adult↗
PubMed1989

Is there a common dopaminergic basis of time perception and reaction time?

The effects of 3 mg haloperidol and 125 mg Madopar on duration discrimination (DD) as well as reaction times were tested in a placebo-controlled, double-blind crossover study with 24 healthy male volunteers. Performance in DD was significantly impaired under haloperidol compared to placebo as well as to Madopar. No changes could be demonstrated for Madopar compared to placebo. Similar results were obtained for measures of reaction time. Significant negative correlations between individual changes in DD and measures of reaction time under each drug condition revealed that subjects with drug-induced impairment in DD also show an increase in reaction times. The nearly identical patterns of drug-induced changes in DD and measures of reaction time may be interpreted in terms of a common neural basis.

Adult↗
PubMed1989

Sex differences in time perception.

In an experiment on discrimination of duration of auditory stimuli in the range of milliseconds 16 men and 16 women were tested. Men scored better than women in discrimination of duration as well as in required session time. These results were discussed in terms of the assumption of a neurotransmitter-related internal clock and with respect to sex differences in reaction time.

Adult↗
PubMed1988

Effects of changes in brain 5-HT activity on indicators of cortical arousal.

Clinical studies on fluoxetine have reported occasional symptoms of increased fatigue in depressed patients. On the other hand, experimental studies in healthy subjects have demonstrated evidence for fluoxetine-induced increases in cortical arousal. The present placebo-controlled study with 24 healthy subjects was designed to answer the following questions: Does fluoxetine increase measures of cortical arousal and decrease feelings of alertness, and does the 5HT2 receptor blocker ritanserin produce inverse effects to fluoxetine? Analyses of covariance revealed the following results: Fluoxetine produced a slight increase, ritanserin a marked decrease in critical flicker fusion frequency. Time perception was slightly improved by both drugs. Self-ratings on alertness and energy were significantly reduced by both fluoxetine and ritanserin as compared to placebo. Effects for fatigue were increased accordingly. Possible underlying neurophysiological mechanisms and specificity of the effects for cortical as opposed to limbic arousal will be discussed.

Adult↗
PubMedDate not supplied

Differential effects of a 5-HT2 receptor blocker on alcohol intake in rats selectively bred for high and low catecholamine responses to stress.

The effect of the selective 5-HT2 receptor blocker ritanserin on alcohol consumption was investigated in two strains of rats selectively bred for high and low catecholamine responses to stress. Rats were forced to drink a 5% alcohol solution for 10 days. For the subsequent six days, animals were injected subcutaneously with 2.5 mg/kg/2 ml ritanserin or vehicle only, and both a 5% solution of alcohol and water were presented to the animals. Ritanserin affected neither water nor total fluid intake. Furthermore, no effect of ritanserin on alcohol consumption could be demonstrated in high-responding rats, whereas in low-responding rats a very pronounced ritanserin-induced reduction in alcohol intake was observed. Results are discussed in terms of mediating effects of serotonergic neurons on mesolimbic dopaminergic reward systems related to drug addiction.

Alcohol Drinking↗