The Journal of Neuroscience, February 15, 1998, 18(4):1345-1362
Optical Mapping of Neural Responses in the Embryonic Rat
Brainstem with Reference to the Early Functional Organization of Vagal
Nuclei
Katsushige
Sato,
Yoko
Momose-Sato,
Akihiko
Hirota,
Tetsuro
Sakai and
Kohtaro
Kamino
Department of Physiology, Tokyo Medical and Dental University
School of Medicine, Bunkyo-ku, Tokyo 113, Japan
We examined the functional organization of the vagal nuclei of the
rat embryo during morphogenesis, using multiple-site optical recording
with a voltage-sensitive dye. Slice preparations with vagus nerve
fibers were dissected from 13- to 16-d-old embryonic (E13-E16) rat
brainstems, and they were stained with the dye. Electrical activity in
response to vagal stimulation was recorded optically from many sites.
In the E13-E14 preparations, two types of spike-like optical signals
were recorded: one was a narrow signal (type I), and the other was a
broader signal (type II). Comparison with the morphology revealed by
DiI labeling suggests that the type I signal response area corresponds
to the nucleus of the tractus solitarius, and the type II signal
response area corresponds to the dorsal motor nucleus of the vagus
nerve. In the E15-E16 preparations, type I signals were followed by a
slow signal related to glutamate-mediated excitatory postsynaptic
potentials, suggesting that synaptic function is organized in the
nucleus of the tractus solitarius by the 15-d-old embryonic stage. In the E14 preparation, a small, slow signal was evoked only in
Mg2+-free solution, implying that postsynaptic
function related to NMDA receptors emerges, in latent form, at the
14-d-old embryonic stage. In the E15 and E16 preparations, although the
nucleus ambiguus is identified morphologically, no neural
response-related optical signal was observed there, indicating that the
embryonic organization of morphology and physiological function is not
necessarily temporally coincident. We have mapped the dynamic
spatiotemporal patterns of the evoked optical signals and have outlined
the early phase of the functional organization of the cranial nuclei
related to the vagus.
Key words:
optical mapping; brainstem; vagal nuclei; development; synaptic activity; voltage-sensitive dye
Copyright © 1998 Society for Neuroscience 0270-6474/98/1841345-18$05.00/0
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