Journal of Neuroscience, Vol 15, 2123-2140, Copyright © 1995 by Society for Neuroscience
Responses to glossopharyngeal stimulus in the early embryonic chick brainstem: spatiotemporal patterns in three dimensions from repeated multiple-site optical recording of electrical activity
K Sato, Y Momose-Sato, T Sakai, A Hirota and K Kamino
Department of Physiology, Tokyo Medical and Dental University School of Medicine, Japan.
In an effort to assess the spatial patterning of glossopharyngeal responses
in the early embryonic chick brainstem, we used a multiple- site optical
recording system with a 12 x 12 element photodiode array and a
voltage-sensitive merocyanine-rhodanine dye (NK2761) to monitor neural
transmembrane voltage activities. Seven and 8 d old embryonic chick
brainstems were sliced into 1400-1600 microns thick sections with the
glossopharyngeal and vagal nerves attached, and then stained with the dye.
Neural voltage-related optical signals were evoked by a positive brief
(depolarizing) square current pulse applied to the glossopharyngeal nerve
with a microsuction electrode, and then recorded simultaneously from many
loci in the objective two-dimensional image plane of a compound microscope.
In addition to the multiple-site optical recording technique, we tried to
introduce an optical sectioning method by changing the focal plane of the
microscope to obtain three-dimensional information. Thus, we have been able
to assess semiquantitatively the three-dimensional profiles of two
glossopharyngeal response areas corresponding to the nucleus of the
glossopharyngeal nerve (nucleus nervi glossopharyngei) and the nucleus of
the tractus solitarius. Furthermore, glutaminergic excitatory postsynaptic
potentials were determined within the response area corresponding to the
nucleus of the tractus solitarius. In addition, we also compared the
glossopharyngeal and vagal response areas and found that the cores of the
related nuclei are separated in three dimensions.
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