Central synapses of spinal motoneurons innervating the trunk swimming muscles of Xenopus laevis embryos.
Our aim was to investigate the presence and nature of central motoneuron synapses within the Xenopus embryo spinal cord. Motoneurons in the rostral trunk were back-filled by applying HRP to the segmented axial swimming muscles on one side of the body. After fixation and DAB processing 4 embryos were selected where many motoneurons were filled and the level of staining was suitable for transmission electron microscopy. Thin transverse sections of the spinal cord showed that central HRP-filled motoneuron processes formed the presynaptic element of chemical synaptic junctions and also made gap junctions with other axons. We discuss the possible role of these synapses in mediating positive feedback excitation to sustain swimming after brief sensory stimulation.
Roberts
A
A
School of Biological Sciences, University of Bristol, UK.
Walford
A
A
D000818:Animals; D001369:Axons / Q000648:ultrastructure; D005246:Feedback; D017629:Gap Junctions / Q000502:physiology / Q000648:ultrastructure; D006735:Horseradish Peroxidase; D008854:Microscopy, Electron; D009046:Motor Neurons / Q000502:physiology / Q000648:ultrastructure*; D018482:Muscle, Skeletal / Q000196:embryology / Q000294:innervation / Q000502:physiology; D013116:Spinal Cord / Q000196:embryology* / Q000502:physiology / Q000648:ultrastructure; D013550:Swimming / Q000502:physiology; D013569:Synapses / Q000502:physiology / Q000648:ultrastructure*; D014982:Xenopus laevis / Q000033:anatomy & histology / Q000196:embryology* / Q000502:physiology
D006735:Horseradish Peroxidase