الفهرس 
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Abstract
The mammillary region occupies the caudal one third of the hypothalamus. This region is occupied by the mammillary complex which consists of the lateral and medial mammillary nuclei (mammillary body), supramamillary nuclei-together with the premammillary nuclei (dorsal and ventral) and the posterior hypothalamic area.
The mammillary nuclei are considered one of the major nuclear groups of the limbic system which are located in the caudal part of the hypothalamus. These nuclei attracted considerable attention because of their apparent involvement in a variety of associative and memory processes.
The mammillary nuclei are considered to play the role of correlation center between the limbic forebrain and midbrain structures. The complex organization of the connections of the mammillary nuclei may provide anatomical substrates for the various functions of these nuclei.
The mammillary nuclei have been involved in a wide variety of diverse functions. These functions include learning and memory, sexual behavior and defensive behavior.
The aim of the present work was to study the postnatal developmental changes of the mammillary nuclei. It also includes the study of the effects of aging on the features of their component neurons.
A total number of 70 albino rats ”wester strain” were used in this study. The age groups of the animals included newborn, ten days, fifteen days, one month, two months and two years old rats. Several histologyical techniques were used in this study. Gallocyanin-chrom alum staining method was used to demonstrate Nissl’s granules, nuclei and nucleoli. Golgi-cox method was used to demonstrate the nerve cells with their processes. Ultrastructural study for the mammillary neurons and their synaptic organization in order to provide an anatomical framework for a better understanding of their functional role by the use of transmission electron microscopic technique was done at the ages of 2 months and 2 years.
Five rats in each age group were processed for Gallocyanin- chrom alum stain and another five were processed in each of the age groups (15 days, one month, 2 months and 2 years) studied by Golgi-cox method. For ultrastructural study of the mammillary nuclei at 2 months and 2 years old animals, ten animals were used in each age group.
By Gallocyanin stain, various mammillary nuclei could be differentiated from each other through their anatomical position and variations in cellular sizes, shapes and staining characteristics. The cellular size and content of Nissl’s granules were increased gradually towards the adult age. By the age of two years, there was a reduction in the amount of Nissl’s granules.
With Golgi stain, the impregnated cells in the mammillary body are characterized by dendritic swellings or varicosities along their dendrites. Some of the dendrites in the lateral mammillary nucleus were markedly beaded compared to those in the medial mammillary nucleus. Also varicosities were noticed on the dendrites of the supramammillary neurons. Dendrites of the lateral mammillary nucleus are relatively aspiny in contrast to other mammillary nuclei which are characterized by somatic and dendritic spines. With advanced age, the mammillary nuclei showed obvious increase in thickness, extension and branching of their dendrites. Also, there is relative increase in dendritic varicosities, somatic and dendritic spines. By the age of two years, the neurons in the mammillary nuclei revealed decrease in the varicosities, thickness and extension of their dendrites with decrease in somatic and dendritic spines relative to the adult age.
The ultrastructural study of the mammillary nuclei in the adult stage demonstrated the presence of small and medium sized cells. The cells are characterized by eccentrically located nuclei with invaginated nuclear envelope and close apposition of the cell membranes of adjacent cells The cytoplasm of medium-sized cells showed large amounts of cytoplasmic orgnelles such as ribosomes, rough endoplasmic reticulum and mitochondria while the small cells showed small amounts of cytoplasmic organelles. There are various types of axosomatic synaptic terminals. The ultrastructure of cells by the age of two years showed evident manifestation of aging in the form of marked invagination of the nuclear membrane as compared with the adult age. Organelles and cytoplasmic vaculation with accumulation of lipofuscin pigment were also detected. No detectable change in the amount of secretory vesicles per terminal as compared with the adult stage.
It was concluded that during the postnatal development of the mammillary nuclei dynamic maturational changes could be detected. These changes are manifested by increase in their cellular content of Nissl substance. Their constituent neurons show progressive increase in dendritic thickness and extension with increase in somatic and dendritic spines. These changes can lead to structural and functional consequences in the mammillary nuclei.
The wide variety of synaptic terminals in the mammillary neurons indicating the presence of several sources that denote the complex organization of the projections to the mammillary nuclei and represent anatomical substrates for different functions.
By the progress of age, there were some degenerative changes in the cells that could lead to impairment of functional activities.