Activity-dependent plasticity in descending synaptic inputs to respiratory spinal motoneurons.
This review focuses on recent evidence for short- and long-term activity-dependent plasticity in descending synaptic inputs to respiratory spinal motoneurons. In anesthetized rats, application of high frequency (100 Hz) conditioning stimulation to descending inputs to phrenic motoneurons elicits short-term potentiation of spontaneous inspiratory bursts. In turtle brainstem-spinal cords in vitro, 10-100 Hz conditioning stimulation elicits short-term potentiation in descending inputs to inspiratory-related serratus motoneurons; 100 Hz stimulation also elicits long-term potentiation in some preparations. In contrast, 1-10 Hz stimulation of descending synaptic inputs to expiratory-related pectoralis motoneurons elicits depression during conditioning stimulation (temporal depression), and long-term depression following stimulation. We hypothesize that inspiratory descending pathways to spinal motoneurons express short-term potentiation, with little evidence for long-term activity-dependent plasticity; other forms of long-lasting plasticity (e.g. serotonin-dependent long-term facilitation) may predominate in these pathways. In contrast, expiratory descending pathways appear biased towards activity-dependent depression possibly to conserve resources during passive expiration.
Johnson
Stephen M
SM
Department of Comparative Biosciences, School of Veterinary Medicine, University of Wisconsin, 2015 Linden Drive, Madison, WI 53706, USA. johnsons@svm.vetmed.wisc.edu
Mitchell
Gordon S
GS
D000818:Animals; D006801:Humans; D009043:Motor Activity / Q000502:physiology*; D009046:Motor Neurons / Q000502:physiology*; D009473:Neuronal Plasticity / Q000502:physiology*; D011712:Pyramidal Tracts / Q000166:cytology / Q000502:physiology; D015656:Respiratory Mechanics / Q000502:physiology*; D013569:Synapses / Q000502:physiology*