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U Henschke

Publications and source records attributed to U Henschke.

4 recordsLinked to original sources
PubMed2003

Pharmacological modulation of cortical excitability shifts induced by transcranial direct current stimulation in humans.

Transcranial direct current stimulation (tDCS) of the human motor cortex results in polarity-specific shifts of cortical excitability during and after stimulation. Anodal tDCS enhances and cathodal stimulation reduces excitability. Animal experiments have demonstrated that the effect of anodal tDCS is caused by neuronal depolarisation, while cathodal tDCS hyperpolarises cortical neurones. However, not much is known about the ion channels and receptors involved in these effects. Thus, the impact of the sodium channel blocker carbamazepine, the calcium channel blocker flunarizine and the NMDA receptor antagonist dextromethorphane on tDCS-elicited motor cortical excitability changes of healthy human subjects were tested. tDCS-protocols inducing excitability alterations (1) only during tDCS and (2) eliciting long-lasting after-effects were applied after drug administration. Carbamazepine selectively eliminated the excitability enhancement induced by anodal stimulation during and after tDCS. Flunarizine resulted in similar changes. Antagonising NMDA receptors did not alter current-generated excitability changes during a short stimulation, which elicits no after-effects, but prevented the induction of long-lasting after-effects independent of their direction. These results suggest that, like in other animals, cortical excitability shifts induced during tDCS in humans also depend on membrane polarisation, thus modulating the conductance of sodium and calcium channels. Moreover, they suggest that the after-effects may be NMDA receptor dependent. Since NMDA receptors are involved in neuroplastic changes, the results suggest a possible application of tDCS in the modulation or induction of these processes in a clinical setting. The selective elimination of tDCS-driven excitability enhancements by carbamazepine proposes a role for this drug in focussing the effects of cathodal tDCS, which may have important future clinical applications.

Adult↗
PubMed1981

Is there a genetic basis for the differences in cancer incidence between Afro-Americans and Euro-Americans?

The data of the Third National Cancer Survey show for many cancer types, large differences in cancer incidence between Euro-Americans and Afro-Americans.(1) As in other racial studies, it is difficult to separate environmental and genetic factors. For the cancers which are more frequent among Afro-Americans, environmental factors seem to be primarily responsible. However, among the cancers less frequent in Afro-Americans, there are some for which the racial differences have a genetic basis. This is clearly the case for skin and lip cancers caused by the ultraviolet B of the sun. Genetic factors are probably also responsible for the racial differences in the incidence of malignant melanomas, testis cancers, astrocytomas, and Ewing's sarcomas. Perhaps there is also a genetic basis for some of the racial differences in the incidence of malignant lymphomas and leukemias. For all these cancers, Afro-Americans are less susceptible. The only cancer to which Afro-Americans appear more susceptible on the basis of genetic makeup, is fibrosarcoma. This is in accord with the high frequency of keloids, a benign counterpart of fibrosarcoma in Afro-Americans.

Africa↗