Light- and electron microscopic characteristics of the vegetative centers in the guinea pig sacral spinal cord intermediate zone.
A dense AChE-negative and NA fluorescent network was visualized by light microscopy in the sacral spinal cord intermediate zone of grown-up guinea pigs of both sexes. This network connects in horizontal and vertical direction the preganglionic vegetative nuclei (n. intermediolateralis pars principalis (ILp), n. intermediolateralis pars funicularis (ILf), n. intercalatus spinalis (IC), n. intercalatus pars paraependimalis (ICpe), (Petras and Cummings 1972) along 2--4 segments of the spinal cord. Electron microscopy demonstrated dense core ves icles (40--100 nm) in the cytoplasm of the ILp cells. The surface of the ILp neurons is covered with synaptic boutons which have clear and dense core vesicles (40--100 nm). The bundles of fibres connecting the vegetative nuclei are built of parallel myelinated fibres and myelinfree axons and dendrites. On their course the axons form varicosites. In the latter and in the synaptic enlargements there are clear and dense core (40--100 nm) vesicles. The probable origin of the vegetative fibres of guinea pig sacral spinal cord is discussed.