title: Short-term plasticity of descending synaptic input to phrenic motoneurons in rats.
abstract: Respiratory afferent stimulation can elicit increases in respiratory motor output that outlast the period of stimulation by seconds to minutes [short-term potentiation (STP)]. This study examined the potential contribution of spinal mechanisms to STP in anesthetized, vagotomized, paralyzed rats. After C(1) spinal cord transection, stimulus trains (100 Hz, 5-60 s) of the C(1)-C(2) lateral funiculus elicited STP of phrenic nerve activity that peaked several seconds poststimulation. Intracellular recording revealed that individual phrenic motoneurons exhibited one of three different responses to stimulation: 1) depolarization that peaked several seconds poststimulation, 2) depolarization during stimulation and then exponential repolarization after stimulation, and 3) bistable behavior in which motoneurons depolarized to a new, relatively stable level that was maintained after stimulus termination. During the STP, excitatory postsynaptic potentials elicited by single-stimulus pulses were larger and longer. In conclusion, repetitive activation of the descending inputs to phrenic motoneurons causes a short-lasting depolarization of phrenic motoneurons, and augmentation of excitatory postsynaptic potentials, consistent with a contribution to STP.
authors.affiliation: Department of Physiology and Institute for Neuroscience, Feinberg School of Medicine, Northwestern University, Chicago, Illinois 60611-3008, USA.
authors.forename: F
authors.initials: F
authors.lastname: Hayashi
authors.forename: C F L
authors.initials: CF
authors.lastname: Hinrichsen
authors.forename: D R
authors.initials: DR
authors.lastname: McCrimmon
mesh_terms: D000818:Animals; D003655:Decerebrate State; D004525:Efferent Pathways / Q000502:physiology; D004558:Electric Stimulation / Q000379:methods; D007395:Interneurons / Q000502:physiology; D008297:Male; D009046:Motor Neurons / Q000502:physiology*; D009473:Neuronal Plasticity; D010791:Phrenic Nerve / Q000502:physiology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D013116:Spinal Cord / Q000502:physiology; D013569:Synapses / Q000502:physiology*; D009435:Synaptic Transmission / Q000502:physiology*; D013997:Time Factors