title: Respiratory function after selective respiratory motor neuron death from intrapleural CTB-saporin injections.
abstract: Amyotrophic lateral sclerosis (ALS) causes progressive motor neuron degeneration, paralysis and death by ventilatory failure. In rodent ALS models: 1) breathing capacity is preserved until late in disease progression despite major respiratory motor neuron death, suggesting unknown forms of compensatory respiratory plasticity; and 2) spinal microglia become activated in association with motor neuron cell death. Here, we report a novel experimental model to study the impact of respiratory motor neuron death on compensatory responses without many complications attendant to spontaneous motor neuron disease. In specific, we used intrapleural injections of cholera toxin B fragment conjugated to saporin (CTB-SAP) to selectively kill motor neurons with access to the pleural space. Motor neuron survival, CD11b labeling (microglia), ventilatory capacity and phrenic motor output were assessed in rats 3-28days after intrapleural injections of: 1) CTB-SAP (25 and 50μg), or 2) unconjugated CTB and SAP (i.e. control; (CTB+SAP). CTB-SAP elicited dose-dependent phrenic and intercostal motor neuron death; 7days post-25μg CTB-SAP, motor neuron survival approximated that in end-stage ALS rats (phrenic: 36±7%; intercostal: 56±10% of controls; n=9; p<0.05). CTB-SAP caused minimal cell death in other brainstem or spinal cord regions.
  1) increased CD11b fractional area in the phrenic motor nucleus, indicating microglial activation; 2) decreased breathing during maximal chemoreceptor stimulation; and 3) diminished phrenic motor output in anesthetized rats (7days post-25μg,
  0.3±0.07V; CTB+SAP: 1.5±0.3; n=9; p<0.05). Intrapleural CTB-SAP represents a novel, inducible model of respiratory motor neuron death and provides an opportunity to study compensation for respiratory motor neuron loss.
authors.affiliation: Department of Comparative Biosciences, University of Wisconsin, 2015 Linden Dr., Madison, WI 53706, USA.
authors.forename: Nicole L
authors.initials: NL
authors.lastname: Nichols
authors.affiliation: Department of Comparative Biosciences, University of Wisconsin, 2015 Linden Dr., Madison, WI 53706, USA.
authors.forename: Stéphane
authors.initials: S
authors.lastname: Vinit
authors.affiliation: Department of Comparative Biosciences, University of Wisconsin, 2015 Linden Dr., Madison, WI 53706, USA.
authors.forename: Lorene
authors.initials: L
authors.lastname: Bauernschmidt
authors.affiliation: Department of Comparative Biosciences, University of Wisconsin, 2015 Linden Dr., Madison, WI 53706, USA. Electronic address: mitchell@svm.vetmed.wisc.edu.
authors.forename: Gordon S
authors.initials: GS
authors.lastname: Mitchell
mesh_terms: D000690:Amyotrophic Lateral Sclerosis / Q000139:chemically induced* / Q000150:complications*; D000818:Animals; D039481:CD11b Antigen / Q000378:metabolism; D002452:Cell Count / Q000379:methods; D016923:Cell Death / Q000187:drug effects; D002772:Cholera Toxin / Q000633:toxicity*; D004195:Disease Models, Animal; D004305:Dose-Response Relationship, Drug; D008297:Male; D009046:Motor Neurons / Q000187:drug effects / Q000502:physiology*; D010791:Phrenic Nerve / Q000503:physiopathology; D010991:Plethysmography; D035422:Pleural Cavity / Q000187:drug effects; D012123:Pulmonary Ventilation; D051381:Rats; D017207:Rats, Sprague-Dawley; D012120:Respiration Disorders / Q000209:etiology*; D012125:Respiratory Center / Q000473:pathology*; D054789:Ribosome Inactivating Proteins, Type 1 / Q000633:toxicity*; D000076985:Saporins; D013997:Time Factors
chemical_list: D039481:CD11b Antigen; D054789:Ribosome Inactivating Proteins, Type 1; C420112:cholera toxin B-saporin conjugate; D002772:Cholera Toxin; D000076985:Saporins
keywords: Breathing; Intercostal; Motor neuron death; Neurodegenerative disease; Phrenic; Spinal cord