Home > Program Faculty > Stephen Johnson Laboratory
- Our laboratory investigates cellular mechanisms underlying neuroplasticity in the spinal cord using in vitro brainstem/spinal cord preparations from young mice and adult turtles that spontaneously produce respiratory motor output. Our working hypothesis is that descending synaptic inputs to respiratory-related spinal motoneurons express short-term (seconds to minutes) and long-term (minutes to hours) changes in synaptic efficacy following different patterns of activity, respiratory insufficiency, or activation of specific spinal receptors.
- A second area of investigation is directed at understanding how respiratory rhythm is generated and modulated in vertebrates using isolated in vitro brainstems from adult turtles. Our working hypothesis is that turtle respiratory rhythm generation requires neurons with intrinsic pacemaker properties. Also, we are studying recently developed models of long-lasting frequency plasticity whereby activation of 5-HT3 or a1-adrenergic receptors in the brainstem causes respiratory frequency to remain increased for several hours.
Mitchell GS, Johnson SM. Invited Review: Neuroplasticity in respiratory motor control. J Appl Physiol 94: 358-374, 2003. [Abstract]
Fuller DD, Johnson SM, Olson EB, Mitchell GS. Synaptic pathways to phrenic motoneurons are enhanced by chronic intermittent hypoxia following cervical spinal cord injury. J Neurosci 23: 2993-3000, 2003. [Abstract]
Johnson SM, Wilkerson JER, Wenninger MR, Henderson DR, Mitchell GS. Role of synaptic inhibition in turtle respiratory rhythm generation. J Physiol (Lond) 544: 253-265, 2002. [Abstract]
Johnson SM, Wilkerson JER, Henderson DR, Wenninger MR, Mitchell GS. Serotonin elicits long-lasting enhancement of rhythmic respiratory activity in turtle brainstems in vitro. J Appl Physiol 91: 2703-2712, 2001. [Abstract]
Johnson SM, Mitchell GS. Activity-dependent plasticity of descending synaptic inputs to spinal respiratory motoneurons in an in vitro turtle brainstem-spinal cord preparation. J Neurosci 20: 3487-3495, 2000. [Abstract]