My research is aimed at understanding the regulation of synapse number, location, and strength, primarily using the frog neuromuscular junction as a
model system. Current interest is centered on developing synapses in a Xenopus nerve-muscle cell culture system, where we use endogenous Ca2+-dependent
K+ (BK) channels as reporters to characterize the �Ca2+ domains� that exist transiently at active zones during presynaptic activity, and correlate the
magnitude and time course of release with local [Ca2+]. We are also studying the changes that occur in the release properties of motor nerve terminals
during development. A second major interest is in the mechanism of robust mechanical modulation of neurotransmitter release from frog motor nerve
terminals by muscle stretch, and the role played by integrins and the presynaptic cytoskeleton. I am collaborating with other faculty in a study of
the effects of overexpression of sarcospan, a component of the dystroglycan complex, on muscle physiology, both in the context of rescuing muscle
structure and function in the mdx mouse model of muscular dystrophy and in the context of changes in structure and function of wildtype mouse muscles.
Finally, I have a long-time interest in the neural adaptations associated with echolocation in different species of bats.
Synapse in Xenopus Nerve-muscle cell culture
Freeze-etch of frog nmj
Sun XP, Chen BM, Sand O, Kidokoro Y, Grinnell AD (2010) Depolarization-induced Ca2+ entry preferentially evokes release of large quanta in the developing Xenopus neuromuscular junction. J Neurophysiol. 104(5):2730-40.
Sun, V.-P., Yazejian, B, and Grinnell, A.D. (2004) Electrophysiological properties of BK channels in Xenopus motor nerve terminals. J. Physiol. 557:207-228
Yazejian, B.M., Sun, X.-P., and Grinnell, A.D. (2000) Tracking presynaptic Ca2+ dynamics during neurotransmitter release with Ca2+-activated K+ channels. Nature Neurosci. 3:566-571.