Peripheral chemoreceptors: postnatal development and cytochemical findings in Sudden Infant Death Syndrome
Andrea Porzionato1, Veronica Macchi1, Anna Parenti2, Luigi Matturri3 and Raffaele De Caro1
1Section of Anatomy, Department of Human Anatomy and Physiology, 2Section of Pathologic Anatomy, Department of Medical Diagnostic Sciences and Special Therapies, University of Padova, Italy and 3Institute of Pathology, University of Milan, Milan, Italy.
Offprint requests to: Raffaele De Caro, M.D. Section of Anatomy, Department of Human Anatomy and Physiology, University of Padua, Via A. Gabelli 65, 35121 Padova, Italy. e-mail: email@example.com
Summary. The aim of the present study is to give a review of the postnatal development of peripheral chemoreceptors - carotid body, paraganglia, and pulmonary neuroendocrine cells (PNEC) - with implications in Sudden Infant Death Syndrome (SIDS). In the postnatal period, the hypoxic chemosensitivity of the carotid body gradually develops. Changes include proliferation of type I and II cells, increased numbers of dense core vesicles and K+ channels, and modifications of neurotransmitter/neuromodulator and receptor expression. Chromaffin paraganglia show increased expression of nitric oxide synthase and neuropeptides, and increased innervation. Innervation of PNEC develops fully only in the first postnatal period, after which their density falls. The neuropeptides produced by PNEC also changes, with increased expression of calcitonin gene-related peptide and neuropeptide YY and reduced expression of calcitonin and gastrin-releasing peptide.
Most of the findings in the carotid body of SIDS victims, i.e., decrease in type I cells and dense cytoplasmic granules, and increase in progenitor cells, indicates immaturity of the carotid body, which may play a role in SIDS in the form of underlying biologic vulnerability. Aorticopulmonary paraganglia hyperplasia and increase of PNEC are also found in SIDS, and may be epiphenomena of alterations of the respiratory function with a pathogenetical role in SIDS. A comprehensive view of the pathogenesis of SIDS should also arise from the integration of peripheral chemoreceptors findings with neuro- and cardiopathologic ones. Histol Histopathol 23, 351-365 (2008)
Key words: Carotid body, Paraganglia, Pulmonary neuroendocrine cells, Sudden infant death syndrome, Autonomic nervous system