Biomedical subjects
Publications and source records attributed to T Rammsayer.
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.
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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.
In a previous study (Rammsayer & Vogel, 1991), rats selectively bred for high and low catecholamine responses to stress showed a selective response to the 5-HT2 receptor blocker ritanserin. However, it remained unclear whether selective breeding resulted in a decrease in 5-HT responsivity, as suggested by the lack of an effect in high stress responding rats, or in an increase in 5-HT responsivity, as suggested by ritanserin-induced reduction in alcohol intake in low-responding rats. To answer this question, nonselectively bred 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 neither affected alcohol nor total fluid intake suggesting that in the general population of N/NIH (Hansen) rats as well as in rats of the same strain selectively bred for high catecholamine responses, mesolimbic dopaminergic activity is not effectively modulated by specific blockade of 5-HT2 receptors. However, a very pronounced ritanserin induced difference in daily water intake between nonbred male and female rats became evident.
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.