Role of Primary Afferents in the Developmental Regulation of Motor Axon Synapse Numbers on Renshaw Cells

Motor function in mammalian species depends on the
maturation of spinal circuits formed by a large variety
of interneurons that regulate motoneuron firing and
motor output. Interneuron activity is in turn modulated
by the organization of their synaptic inputs, but the
principles governing the development of specific synap-
tic architectures unique to each premotor interneuron
are unknown. For example, Renshaw cells rec eive, at
least in the neonate, convergent inputs from sensory
afferents (likely Ia) and motor axons, raising the ques-
tion of whether they interact during Renshaw cell devel-
opment. In other well-studied neurons, such as Purkinje
cells, heterosynaptic competition between inputs from
different sources shapes synaptic organization. [Continue Reading]