The development of swimming was investigated in zebrafish aged 1.5 to 5 days postfertilization by examining both the swimming behavior and its generation by the nervous system. Upon hatching (at day 2), swimming is undirected and occurs in sustained bursts of high frequency (mean = 67 Hz) tail undulations. By 4 days, the swimming pattern matures to a more directed, less erratic, beat-and-glide pattern where slower (mean = 35 Hz) tail undulations, lasting ∼200 ms, alternate with longer gliding rest periods. Swimming is powered by two classes of embryonic muscles (embryonic red, ER and white, EW) that are electrically coupled within (but not between) classes and have physiological properties similar to vertebrate tonic and twitch muscle, respectively. ER fibers have a lower chloride ion permeability than EW fibers and do not have sodium dependent action potentials. In paralyzed preparations, motoneurons and muscle fibers received coordinated excitatory synaptic activity (with left to right alternation and head to tail propagation) corresponding to either burst or beat-and-glide swimming. ER muscle was de-recruited at the fastest swimming rates and EW fibers dropped out at the slowest swimming rates. Rhythmic motoneuron output was generated by a phasic glutamatergic and a largely tonic glycinergic synaptic drive. Glutamatergic synapses had either or both AMPA/kainate and NMDA receptors and the kinetics of these synaptic currents were fixed throughout the developmental period examined. When depolarized, motoneurons fired high frequency (up to 800 Hz) bursts of action potentials that rapidly accommodated (within ∼20 ms) due to voltage and calcium dependent outwardly rectifying conductances. These intrinsic motoneuron properties are hypothesized to interact with the rhythmic synaptic drive to pattern motor output (at ∼25--75 Hz) to locomotor muscles. The neural generation of swimming in developing zebrafish is thus fundamentally similar to locomotion in adu
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:QMM.38468 |
| Date | January 2002 |
| Creators | Buss, Robert R. |
| Contributors | Drapeau, Pierre (advisor) |
| Publisher | McGill University |
| Source Sets | Library and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada |
| Language | English |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Format | application/pdf |
| Coverage | Doctor of Philosophy (Department of Biology.) |
| Rights | All items in eScholarship@McGill are protected by copyright with all rights reserved unless otherwise indicated. |
| Relation | alephsysno: 001954120, proquestno: NQ85689, Theses scanned by UMI/ProQuest. |
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