Abstract
The present study aimed to elucidate the histological, histochemical, and ultrastructural structures of the neonatal stomach in local male hamsters (Mesocricetus auratus), with special emphasis on regional differentiation and the parietal cells development. Twelve healthy neonatal male hamsters were used and divided into two groups: first one was used for histological and histochemical investigations and the other one for ultrastructural examinations using the transmission electron microscope (TEM). The tissue samples were collected from the non-glandular region and from the cardiac, fundic, and pyloric regions of the stomach. The routine histological staining Hematoxylin and Eosin, Masson’s Trichrome and combined Periodic Acid Schiff Alcian Blue (pH 2.5) techniques were employed to assess tissue organization and nature of mucin. The histological findings showed clear differentiation between the non-glandular and the glandular compartments of the neonatal stomach. The non-glandular region was lined by thin keratinized stratified squamous epithelium, consistent with the neonatal dietary requirements. The glandular stomach part exhibited distinct cardiac, fundic, and pyloric regions. The cardiac and pyloric glands were predominantly composed of mucous-secreting cells and sparse parietal cells, while the chief cells were absent or rare. In contrast, the fundic region display a well-developed fundic glands contained abundant chief cells and moderate number of parietal cells, which indicat early functional specialization. The histochemical examinations demonstrated the predominance of the neutral mucins in both surface epithelial cells and gastric pits across all glandular regions. The ultrastructural examination confirmed early functional maturation of the gastric parietal cells, characterized by a large euchromatic nucleus, extensive intracellular canalicular systems lined with microvilli, numerous mitochondria with well-developed cristae, and prominent rough endoplasmic reticulum, reflect the active hydrochloric acid secretion. In conclusion, the neonatal male hamster stomach showed advanced regional and cellular differentiation shortly posts birth. These results provide a comprehensive morphological and ultrastructural baseline for understanding postnatal gastric development and functional maturation in the rodents, supporting the use of Mesocricetus auratus as a valuable experimental model in comparative and developmental gastro-histological studies.

Key words: Hamster, Neonate, Histochemical, Histology, Stomach, Parietal cells, Ultrastructure.