Durable sensitization of hormone receptors during differentiation in regenerating planarians by treatment with homologous or analogous hormone molecules.

Hormonal (dopamine, epinephrine) treatment of planarians during total regeneration (sensitizing treatment) resulted in amplification of the receptors, which accounted for an increased response to later hormone exposure (provocative treatment). While not presensitized specimens showed an identical increase of glucose uptake upon provocative treatment with either hormone, dopamine proved to be more active than epinephrine regardless of homologous or analogous presensitization. The glucose-uptake-enhancing effect of dopamine was independent of the presensitizing dose level, whereas that of epinephrine was not, having increased as the presensitizer concentration was elevated. The experimental observations indicate that the hormone receptors may become modified, i.e. durably amplified, during the differentiation stage and that exposure of the differentiating receptor to a structurally dissimilar, analogous molecule may result not only in deformation, but also in amplification of the receptor.