[5-hydroxytryptophan decarboxylase (5-HTPD) and monoamine oxidase (MAO) activities in the embryonic pineal organ of Lacerta vivipara J. A qualitative and quantitative microscopic study of the uptake of 3H-5-HTP under experimental conditions and the histochemistry of MAO (author's transl)].

Experiments involving combined injections of a drogue (Ro4-4602 or nialmide) and precursor (3H-5-HTP) allowed to determine the best conditions for performing an experimental study of serotonin (5-HT) synthesis and metabolism in the embryonic pineal organ of Lacerta vivipara. Inhibition of 5-HT synthesis at the decarboxylation step using Ro4-4602 significantly reduces the tritiated indolamine rates in the pineal sensory epithelium of embryos of the stages 37-40. In contrast with the embryos of stages 36 to 40 which received injections of 3H-5-HTP only, the secretory rudimentary photoreceptor cells (SRP) of embryos of the same stages which were pretreated with Ro4-4602 do not show a selective radioautographic labeling. After inhibition of the monoamine oxidases with nialomide, the tritiated indolamine rates are significantly increased in the SRP of embryos of stages 35 to 40. Our radioautographic studies show indirectly the early presence of 5-HTPD and MAO in the SRP (stage 35) during the pineal embryogenesis of Lacerta. In the distal part of the pineal, monoamine oxidase activity is histochemically demonstrated at stage 34. During ontogenesis, the reaction becomes increasingly intensive in the apical part of the epithelial cells while it extends to the epithelium of the proximal part of the pineal organ.