Demonstration of dopamine in electron-dense synaptic vesicles in the pars intermedia of Xenopus laevis,by freeze substitution and postembedding immunogold electron microscopy |
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Authors: | F. J. C. van Strien E. P. C. T. de Rijk P. S. H. Heymen T. G. M. Hafmans E. W. Roubos |
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Affiliation: | (1) Department of Animal Physiology, Faculty of Science, University of Nijmegen, Toernooiveld, NL-6525 ED Nijmegen, The Netherlands;(2) Department of Anatomy and Embryology, University of Nijmegen, The Netherlands |
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Abstract: | Summary The presence of dopamine in the pituitary of the clawed toad Xenopus laevis was studied by light and electron microscope immunocytochemistry, using pre- and postembedding techniques. Light microscopy showed the presence of an intricate, anti-dopamine-positive fibre network throughout the pars intermedia. In preembedded stained material, dopamine appeared to occur in varicosities which make synaptic contacts with both folliculo-stellate cells and melanotrope cells. Postembedding immunogold staining of freeze-substituted material permitted the localization of anti-dopamine reactivity in electron-dense vesicles in these varicosities. This finding supports the hypothesis that dopamine is involved in the (inhibitory) control of melanotrope cell activity in X. laevis. |
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