Motor neurons in the vertebrate spinal cord are stereotypically organized along the rostro-caudal axis in discrete columns that specifically innervate peripheral muscle domains. Originating from the same progenitor domain, the generation of spinal motor neurons is orchestrated by a spatially and temporally tightly regulated set of secreted molecules and transcription factors such as retinoic ac...

Identified neurons in the cerebropleural ganglion (brain) of the mollusc Pleurobranchaea were stimulated and recorded from intracellularly while recording the identified motor program from buccal muscles (reduced preparation) or nerves (isolated central nervous system). Neurons studied included the metacerebral giant neurons (MCGs), phasic paracerebral neurons (PCp's), polysynaptic excitors of ...

The identity of motor neurons diverges markedly at different rostrocaudal levels of the spinal cord, but the signals that specify their fate remain poorly defined. We show that retinoid receptor activation in newly generated spinal motor neurons has a crucial role in specifying motor neuron columnar subtypes. Blockade of retinoid receptor signaling in brachial motor neurons inhibits lateral mot...

Spinal muscular atrophy (SMA), characterized by specific degeneration of spinal motor neurons, is caused by mutations in the survival motor neuron 1 (SMN1) gene and subsequent decreased levels of functional SMN. How the deficiency of SMN, a ubiquitously expressed protein, leads to spinal motor neuron-specific degeneration in SMA patients remains unknown. In this study, we examined the role of S...

Spinal muscular atrophy (SMA), characterized by specific degeneration of spinal motor neurons, is caused by mutations in the survival motor neuron 1 (SMN1) gene and subsequent decreased levels of functional SMN. How the deficiency of SMN, a ubiquitously expressed protein, leads to spinal motor neuron-specific degeneration in SMA patients remains unknown. In this study, we examined the role of S...

Acute intermittent hypoxia (AIH) induces a form of spinal motor plasticity known as phrenic long-term facilitation (pLTF); pLTF is a prolonged increase in phrenic motor output after AIH has ended. In anesthetized rats, we demonstrate that pLTF requires activity of the novel PKC isoform, PKCθ, and that the relevant PKCθ is within phrenic motor neurons. Whereas spinal PKCθ inhibitors block pLTF, ...

α-Motor neurons receive synaptic inputs from spinal and supraspinal centers that comprise components either common to the motor neuron pool or independent. The input shared by motor neurons--common input--determines force control. The aim of the study was to investigate the changes in the strength of common synaptic input delivered to motor neurons with changes in force and with fatigue, two co...

We describe synaptic connections through which information essential for encoding efference copies reaches two coordinating neurons in each of the microcircuits that controls limbs on abdominal segments of the crayfish, Pacifastacus leniusculus. In each microcircuit, these coordinating neurons fire bursts of spikes simultaneously with motor neurons. These bursts encode timing, duration, and str...

1 Are motor neurons just passive relayers of the signals they receive? Or, do motor 2 neurons shape the signals before passing them on to the muscles, thereby influencing 3 the timing of motor behavior? Few direct tests of the role of motor neuron intrinsic 4 properties in shaping motor behavior have been carried out, and many questions remain 5 about the role of specific ion channel genes in m...

Motor function depends on the formation of selective connections between sensory and motor neurons and their muscle targets. The molecular basis of the specificity inherent in this sensory-motor circuit remains unclear. We show that motor neuron pools and subsets of muscle sensory afferents can be defined by the expression of ETS genes, notably PEA3 and ER81. There is a matching in PEA3 and ER8...