[Topography and structural characteristics of the synapses of the reticulospinal system in the frog brain].

Distribution and ultrastructure of the synapses formed by axons of the reticular formation cells in the medulla oblongata have been studied in the motoneurons of the frog (Rana ridibunda) spinal cord after a unilateral destruction in the area of the medial and ventral nuclei of the reticular formation. Some synapses with signs of degeneration have been revealed in the motonuclei neuropil, on the perikaryon and proximal areas of the dendrites. Chemical synapses of the axosomatic, axodendritic (axospinous including) and axo-axonal types have been revealed. The axodendritic synapses have connections of the gap junction type. Therefore, it is possible to suppose that the synapses of the reticulo-spinal fibres can ensure a dual mechanism for impulse transmission. When comparing the data obtained at the light optic and electron microscopic investigations, it is evident that the ventro-lateral areas of the spinal motor nuclei make the region where the reticulo-spinal fibres terminate.