Pyridoxine treatment alters embryonic motility in chicks: Implications for the role of proprioception.

Somatosensory feedback is important for the modulation of normal locomotion in adult animals, but we do not have a good understanding of when somatosensory information is first used to modulate motility during embryogenesis or how somatosensation is first used to regulate motor output. We used pyridoxine administration (vitamin B6 ), which is known to mostly kill proprioceptive neurons in adult mammals and embryonic chicks, to explore the role of proprioceptive feedback during early embryonic motility in the chick. Injection of pyridoxine on embryonic day 7 (E7) and E8 reduced the amplitude of leg movements recorded on E9 and the number of large, healthy neurons in the ventral-lateral portion of the DRGs. We conclude that proprioception is initially used during embryogenesis to modulate the strength of motor output, but that it is not incorporated into other aspects of pattern generation until later in development as poly-synaptic pathways develop.