Histochemical Fluorescence of Raphe Neurons: Selective Enhancement by Tryptophan

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Science  11 Jun 1971:
Vol. 172, Issue 3988, pp. 1159-1161
DOI: 10.1126/science.172.3988.1159


The histochemical fluorescence of those neurons in brainstem raphe nuclei which are presumed to contain serotonin is selectively and stereospecifically enhanced by L-tryptophan at doses that also produce an elevation in the concentration of serotonin. However, contrary to our assumptions, the increase in raphe fluorescence is not prevented by p-chlorophenylalanine, an inhibitor of serotonin synthesis. These results suggest that under some conditions derivatives of tryptophan other than, or in addition to, serotonin may be of significance in raphe neurons.