Reticulospinal neurons, locomotor control and the development of tailswimming in Xenopus.
The development of early swimming in Xenopus occurs early during the embryonic period and within a few hours. Between stages 25 and 33 the central nervous system reaches a state of 'critical mass' at which the for swimming necessary body structures have partly developed, thus enabling the embryo to move through the water. The pattern of undulatory body movements is formed within the pattern generators in the central nervous system (CNS) involving different types of neurons in the spinal cord and brainstem. Tailswimming in Xenopus embryos can be evoked by tactile stimuli, light or vibrations. Here the development of brainstem-spinal connections and their possible role in swimming caused by external stimuli will be discussed. It is now clear that reticulospinal neurons are among the first neurons that differentiate within the CNS, their axons enter the spinal cord when the first swimming movements occur, that they are active in a motoneuron-like fashion, during--and involved in the control of early tailswimming. Among the reticulospinal neurons only the Mauthner cell seems to serve a command function.
van Mier
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Department of Medical Physics and Biophysics, University of Nijmegen, The Netherlands.
D000818:Animals; D007814:Larva; D008124:Locomotion; D009474:Neurons / Q000502:physiology*; D012154:Reticular Formation / Q000502:physiology*; D013550:Swimming; D014981:Xenopus / Q000254:growth & development*