THE SUBMICROSCOPIC STRUCTURE OF THE VENTROLATERAL SUBDIVISION OF THE MIDBRAIN PERIAQUEDUCTAL GRAY OF THE RAT / 解剖学报

ABSTRACT

The transmission electron microscopic technique was used in the present study to observe the normal ultrastructure of the ventrolateral subdivision (VLS) of the rat midbrain periaqueductal gray (PAG). Most of the neurons in the VLS of PAG had medium-sized fusiform neuronal cell body, ellipsoid nucleus and irregular nuclear membrane with deep invaginations or infoldings. The nucleolus was electron dense, large and spheroidal. There were many kinds of organelles in the cytoplasm and the Golgi apparatus in some cells were circular or semicircular. The percentage of axo-somatic synapse in total synapses in VLS was 6% and most of them was of symmetric type (82%). Axo-dendritic synapses counted 94%, of these 66% were symmetric type, 34% were asymmetric. Some special types of axo-dendritic synapse were observed. e. g., axo-spine synapse, parallel synapse, and central dendritic synaptic glomerulus. The synaptic vesicles in the presynaptic bags of the synapses mentioned above were mainly clear spherical in type, and most of the clear spherical vesicle-filled bags contained a few flattened vesicles and granular vesicles. Only a few bags were mainly filled with flattened vesicles.