Ultrastructural studies on calcitonin gene-related peptide-, tachykinins- and somatostatin-immunoreactive neurones in rat dorsal root ganglia: Evidence for the colocalization of different peptides in single secretory granules |
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Authors: | Adalberto Merighi Professor Julia M Polak Sally J Gibson Sergio Gulbenkian Karen L Valentino Saverio M Peirone |
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Institution: | (1) Department of Histochemistry, Royal Postgraduate Medical School, Hammersmith Hospital, London, UK;(2) Istituto di Anatomia Veterinaria Sistematica e Comparata, Torino, Italy;(3) Department of Psychiatry and Behavioral Sciences, R-321 Stanford University School of Medicine, Stanford, California, USA;(4) Department of Histochemistry, Royal Postgraduate Medical School, Du Cane Road, W12 OHS London, UK |
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Abstract: | Summary Calcitonin gene-related peptide (CGRP)-, tachykinins- and somatostatin-immunoreactive neurones in rat dorsal root ganglia have been studied by means of single and double immunogold labelling techniques. Peptide-immunoreactive neurones are generally B- or C-type cells of small size, with well developed rough endoplasmic reticulum and scanty neurofilaments. In neurones classifiable as A2-type cells, i.e. larger neurones with a lighter cytoplasm due to the presence of poorly developed Nissl bodies and numerous neurofilaments, only CGRP immunoreactivity was detected. Immunolabelled structures were identified as large (60–100 nm diameter), electron-dense, membranebounded p-type granules. They were observed only in neuronal cell bodies or in the intraganglionic portions of the axons. No granules immunoreactive to the antisera applied in this study were observed in non-neuronal cells. Immunostaining experiments with different combinations of the antisera revealed, in some cells, the presence of double immunolabelled granules; in particular localization of CGRP and tachykinins, CGRP and somatostatin, and tachykinins and somatostatin to single secretory granules was demonstrated. The finding that more than one peptide is localized to the same secretory granule supports the postulate that peptides are co-released upon nerve stimulation providing morphological support for physiological and pharmacological data demonstrating an interaction between different peptides in the modulation of synaptic activity. |
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Keywords: | Primary sensory neurones Immunogold Neuropeptide colocalization Tachykinins Somatostatin Calcitonin gene-related peptide Rat (Wistar) |
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