Vertebrate motor control networks initially assemble before movements begin and continue to develop until mature motor behaviour is in place. The underlying mechanisms of motor control have been investigated at different stages of development and using many animal model systems, e.g. mouse, lamprey, zebrafish and frog tadpole. Compared to mammalian spinal neural circuitry, the network controlling swimming in Xenopus tadpoles is a much simpler and experimentally more amenable model system. At the time of hatching (stage 37/38) Xenopus tadpoles are only able to generate a stereotyped swimming activity, and the underlying mechanisms mediating this simple swimming pattern have been extensively explored. Just 24 hours later, at stage 42, a much more flexible swimming behaviour appears, but tadpoles still mainly lie dormant. By stage 44, they join the water column and become free swimming. During this developmental period, a suite of anatomical and physiological changes occur. Using patch clamp recordings the developmental changes of central pattern generator (CPG) neurons in the spinal cord can be characterised, and the regulation of these neurons by neurotransmitters and neuromodulators can be investigated. Results from simple systems like the Xenopus tadpole, and indeed other aquatic vertebrates such as zebrafish, are fundamental to our understanding of more mature and / or complex motor systems. I plan to investigate how the expression and kinetics of ion channels and pumps determine CPG neuron activity, and furthermore how CPG networks are affected by spinal cord injury, and network recovery during regeneration.
For further information, please also see: http://www.cnr.ed.ac.uk/Research/hongyan.html
Zhang HY., Sillar KT. (2012) Short-term memory of motor network performance via activity-dependent potentiation of Na+/K+ pump function. Curr. Biol., 22 (6) : 526-31.
Zhang HY., Issberner J., Sillar KT. (2011) The development of a locomotor rheostat. Proc. Natl. Acad. Sci. U S A, 108 (28) : 11674-9.
Zhang HY., Li WC., Heitler WJ., Sillar KT. (2009) Electrical coupling synchronises spinal motoneuron activity during swimming in hatchling Xenopus tadpoles. J Physiol., 587 (Pt 18): 4455-66.
Zhang HY., Langeslag M., Breukels V., Jenks BG., Roubos EW., Scheenen WJJM. (2008) Calcium channel kinetics of melanotrope cells in Xenopus laevis depend on environmental stimulation. Gen. Comp. Endocrinol., 156 (1) : 104-12.
2013 Chancellor´s Fellowship, University of Edinburgh, UK