Histological study of the taste buds of the circumvallate papilla in the tongue of male albino rat in different ages

ABSTRACT

Twenty male albino rats were utilized in this study to investigate the histological, and ultrastructural modification in the circumvallate papillae of male albino rat with special attention to the development of taste bud during prenatal, postnatal development and aging. The animals were divided into five groups [four animals each] according to the their age Group A prenatal animals [18-19 day of gestation] group B [0 day old] group C [2 week old, group D [adult 5-7 months] and group E senile [18-24 months]. The animals were anaesthetized using ether inhalation, their tongues were dissected immediately and processed for light and electron microscope examinations. The circumvallate papilla of the prenatal group was dome shaped elevation covered with non keratinized stratified squamous epithelium and surrounded by a closed furrow from both sides, No taste buds were observed. In 0 day old rats the circumvallate papilla was surrounded by a partially obliterated furrow and the papillary wall was lined by immature taste buds, formed of few clusters of dark and light cells without taste pore. Their nuclei were found at the apical and basal poles of the buds, also unmyelinated nerve fibers were detected between these cells. By the age of two weeks the circumvallate papilla was surrounded by an opened furrow which lined by immature taste bud without taste pore. Many light cells and some dark cells were noticed on the apical and basal pole of the buds. In addition unmyelinated nerve fibers were detected between taste cells. In adult group, the circumvallate papilla was surrounded by an opened furrow and its wall was lined by many mature taste buds with taste pores. Each task bud was formed of elongated cells, that converge at the taste pore, their nuclei occupied the basal half of the bud. The taste bud was formed of dark, light, intermediate and basal cells. The dark cells were small irregular in their outline with electron dense cytoplasm and nuclei. They extended cytoplasmic processes that separated and surrounded the other taste cells and intragemmal nerve fibers. The apical part of these cells contained dense secretory granules. The light cells were larger than dark cells and contained large smooth outline oval. They were characterized by electron lucent vesiculated cytoplasm. The intermediate cells were less common type of cells found in the adult rat taste buds. They were found to share characteristic of both light and dark cells and their cytoplasm were moderate in electron density between light and dark cells. In senile group, the circumvallate taste buds were formed from few elongated cells that converge at the taste pore and their nuclei occupied the basal half of the bud. Each taste bud was formed of dark and light cells. The dark cells were the commonest cell type and they were small irregular in outline with electron dense cytoplasm and nuclei. Few light cells with electron lucent cytoplasm and large oval nuclei Unmyelinated nerve fibers were observed between these cells. It become clear that the peripheral gustatory system was maintained histologically over a wide age range. Thus the change in the taste acuity reported in old age may be due to histological or biochemical changes in the taste cells