Modeling calyx-like synapses on Type I hair cells

[rcalinjageman]

Type I hair cells in the vestibular system have a rather unusual synaptic contact with central afferent fibers. The base of each type I cell is completely enveloped in a large calyx-like post-synaptic terminal. For an example, see this figure: http://neuro.med.harvard.edu/faculty/im ... hslice.jpg


I was wondering if it would be possible to model such a structure using Neuron---I can't think of a way this could be easily decomposed into cylinders.

Any suggestions? Thanks,

Bob Calin-Jageman

[ted]

If a structure has a geometry that diverges significantly from a cylinder, its
detailed electrical properties cannot be represented by a cable; a more general finite
element approach would be needed. But the first thing that comes to my mind is that
it would be sufficient to represent the electrical properties of the presynaptic "blob"
and the postsynaptic "cup" with single compartments.

How to represent chemical signaling in these structures is potentially a more difficult and
interesting problem, and one that would have to be dealt with at the level of NMODL
(as with all "accumulation mechanisms"). A concentric shell geometry with spherical
symmetry might be sufficient, unless there are multiple active zones, significantly
nonuniform distributions of organelles, calcium waves etc..