Topographical distribution of the astrocytic lamellae in the hypothalamus.

The distribution of astrocytic lamellae in hamster hypothalamus was studied by electron microscopy. The astrocytic lamellae (AL) are laminar expansions of the larger astrocyte processes devoided of cell organelles. In this paper, we describe the stratified structures of astrocytic lamellae which are found according to the following patterns: surrounding neuronal somata or delimiting one soma from the other, somata from blood vessels or from neuropile. In addition, layers of astrocytic lamellae are found surrounding nervous processes, blood vessels and forming a part of the subpial layer, as well as delineating the synaptic endings. Therefore, the astrocytic lamellae form a network through the hypothalamic components. The functional significance of these structures is discussed in relation to the physiologic studies on astrocytic membranes, as a basis for the understanding of their role in neuron metabolism.