title: Dedifferentiation of intrinsic response properties of motoneurons in organotypic cultures of the spinal cord of the adult turtle.
abstract: Explant cultures from the spinal cord of adult turtles were established and used to study the sensitivity of the intrinsic response properties of motoneurons to the changes in connectivity and milieu imposed by isolation in culture. Transverse sections 700 microm thick were explanted on cover slips and maintained in roller-tube cultures in medium containing serum and the growth factors brain-derived neurotrophin factor (BDNF), neurotrophin-3 (NT3), glial cell line-derived neurotrophic factor (GDNF) and ciliary neurotrophic factor (CNTF). The gross morphology of acute sections was maintained after 4 weeks in culture. Cell bodies of motoneurons remained stainable in fixed cultures with an antibody against choline acetyltransferase (ChAT) throughout the culture period. During culture, motoneurons maintained stable resting membrane potentials and were contacted by functional synapses. The ability to generate action potentials was also preserved as was delayed inward rectification and generation of calcium spikes in the presence of tetra-ethyl ammonium (TEA). In response to depolarization, however, motoneurons presented strong outward rectification, and only 41% of the cells recorded from maintained the ability to fire repetitively. By the second week in culture, a fraction of motoneurons displayed fast and slow transient outward rectification and low-threshold calcium spikes, features not seen in turtle motoneurons in acute slices. On the other hand, properties mediated by L-type Ca2+ channels disappeared during the first few days in culture. Our observations show that the phenotypical intrinsic response properties of mature spinal motoneurons are modified in explant cultures. The properties acquired resemble the properties in juvenile motoneurons in several species of terrestrial vertebrates.
authors.affiliation: Department of Medical Physiology, Panum Institute, University of Copenhagen, Denmark.
authors.forename: J F
authors.initials: JF
authors.lastname: Perrier
authors.forename: J
authors.initials: J
authors.lastname: Noraberg
authors.forename: M
authors.initials: M
authors.lastname: Simon
authors.forename: J
authors.initials: J
authors.lastname: Hounsgaard
mesh_terms: D000200:Action Potentials / Q000187:drug effects / Q000502:physiology; D000367:Age Factors; D000818:Animals; D019208:Brain-Derived Neurotrophic Factor / Q000494:pharmacology; D002454:Cell Differentiation / Q000187:drug effects / Q000502:physiology; D002586:Cesium / Q000494:pharmacology; D002712:Chlorides / Q000494:pharmacology; D020934:Ciliary Neurotrophic Factor / Q000494:pharmacology; D003515:Cycloleucine / Q000031:analogs & derivatives / Q000494:pharmacology; D004594:Electrophysiology; D051100:Glial Cell Line-Derived Neurotrophic Factor; D009046:Motor Neurons / Q000166:cytology* / Q000502:physiology*; D009414:Nerve Growth Factors; D009419:Nerve Tissue Proteins / Q000494:pharmacology; D018696:Neuroprotective Agents / Q000494:pharmacology; D020933:Neurotrophin 3 / Q000494:pharmacology; D009924:Organ Culture Techniques; D013116:Spinal Cord / Q000166:cytology* / Q000502:physiology*; D013569:Synapses / Q000502:physiology; D019789:Tetraethylammonium / Q000494:pharmacology; D013779:Tetrodotoxin / Q000494:pharmacology; D014426:Turtles
chemical_list: D019208:Brain-Derived Neurotrophic Factor; D002712:Chlorides; D020934:Ciliary Neurotrophic Factor; D051100:Glial Cell Line-Derived Neurotrophic Factor; D009414:Nerve Growth Factors; D009419:Nerve Tissue Proteins; D018696:Neuroprotective Agents; D020933:Neurotrophin 3; D003515:Cycloleucine; C036361:1-amino-1,3-dicarboxycyclopentane; D002586:Cesium; D013779:Tetrodotoxin; D019789:Tetraethylammonium; C028019:cesium chloride