DIFFERENTIAL DISTRIBUTION OF 6 CALCIUM-BINDING PROTEINS IN THE RAT OLFACTORY EPITHELIUM DURING POSTNATAL-DEVELOPMENT AND ADULTHOOD

Odorant stimulation of receptor cells results in a calcium influx that activates the transduction pathway. Ca2+ accepters, such as calmoduli n, may mediate between the change in intracellular calcium and the con ductance mechanism underlying the initial electrical event. Ca2+ accep ters also may participate in subsequent processing of olfactory inform ation. The identification and characterization of these molecules, the refore, should provide important information about the complex signal transduction pathway involving calcium in olfaction as well as other s ensory systems. The present study describes the distribution of six ca lcium-binding proteins in the rat main olfactory epithelium during pos tnatal development to determine when different Ca2+ accepters can be d etected and whether they segregate into different layers or portions o f the epithelium. Calmodulin, calretinin, calbindin-D28k, neurocalcin, and recoverin were detected immunohistochemically in olfactory recept ors but not in basal cells. S-100 immunoreactivity was restricted to g lial cells primarily around the cribriform plate. During postnatal dev elopment (from P1 to P20), calmodulin, calretinin, calbindin-D28k, and neurocalcin formed a gradient of immunoreactivity descending from the central to the lateral areas in the nasal cavity, whereas recoverin w as expressed only in sporadic, mature receptors in the proximal region of the mucosa. At P20, the immunoreactivity pattern for each calcium- binding protein was identical to the adult profile, indicating that th e olfactory epithelium had reached maturity by this stage. Olfactory n erve fiber bundles displayed a differential staining pattern from P1 u ntil adulthood for calbindin-D28k and calretinin (internal portions of bundles). Differential calmodulin immuno-reactivity of olfactory nerv es (large external portions of bundles) appeared at P10. The immunorea ctivity of the nerve fiber bundles may reflect a further degree of org anization relevant to odor discrimination. (C) 1995 Wiley-Liss, Inc.