[The structural organization of the synaptic connections of the motor neurons in the mammalian spinal cord].

Peculiarities of the synaptic organization of the motor neurons of the spinal cord of the rodents (rats), predators (cats), primates (Macaca rhesus monkeys) were studied in the early stages of the postnatal ontogenesis and in the adult animals. The motor nucleus region of the lumbar thickening was studied both in normal animals and after the experimental destruction of cerebral nuclei. A new view on the structural-spatial organization of the motor neuron dendrites, the branches of which are highly specialized in the perception of the efferent inputs, is gained. By means of light and electron microscope, the types of synapses, composed of the terminations of the fibers of three major supraspinal systems of the motor control (reticulo-, vestibulo- and rubro-spinal) were studied. Lower mammals are found to have electrotonic and mixed electro-chemical synapses, along with the chemical ones. The fundamental regularities of the distribution of the synaptic inputs of different modality on the somato-dendritic membranes of the motor neurons, specifically the grouping of the chemical synapses and definitive regions of the membrane and those of electrical ones in one microzone were stated. The functional significance of the different types of synapses is discussed with the reference to modern neurology data.