Adenosine Triphosphate (ATP), acting via ionotropic (P2X) and metabotropic (P2Y) receptors, is well established as a neurotransmitter in sensory systems. It is also involved in modulating rhythmic motor behaviors (eg. locomotion, respiration) through actions on central rhythm generating circuits (Dale & Gilday, 1996 Nature 383 p259; Lorier et al, 2002 SFN Abst 173.8 ) and MNs (Miles et al, 2002 J Appl Physiol 92 p1899). To further explore the role of ATP signaling in motor control, we used whole-cell recording techniques to characterize, during postnatal development, the effects of ATP on esophageal MNs of the compact formation of nucleus Ambiguus (cNA), the final output cells for the swallowing central pattern generator. Medullary slices containing the cNA were prepared from neonatal (P0-4) and juvenile (P15-21) rats. In a majority of neonatal cNA MNs (58/78 cells), local application of 1mM ATP produced a large (-180±20 pA), desensitizing (τ=6.2±0.4 ms), PPADS-sensitive (10µM, n=4) inward current that was...