The Journal of Neuroscience, April 1, 2003, 23(7):2932
Contribution of Excitatory Chloride Conductance in the
Determination of the Direction of Traveling Waves in an Olfactory
Center
Satoshi
Watanabe,
Tsuyoshi
Inoue, and
Yutaka
Kirino
Laboratory of Neurobiophysics, Graduate School of Pharmaceutical
Sciences, The University of Tokyo, Bunkyo-ku, Tokyo 113-0033, Japan
Traveling waves have been found in the CNS of vertebrates
and invertebrates. In the olfactory center [procerebrum (PC)] of the
terrestrial slug Limax, periodic waves travel from the
apex to the base with a frequency of ~0.7 Hz. The oscillation and
propagation of waves have been thought to be mediated by the mutual
connections of bursting neurons in the PC. The direction of the wave is
Cl
dependent, because lowering the
Cl concentration in the medium reverses the
direction. The bursting neurons have a Cl
channel-coupled glutamate receptor (GluClR), and, using a calcium imaging technique, the receptor was found to be excitatory. Activation of the GluClR with its selective agonist ibotenate resulted in an
increased frequency of the oscillatory neural activity recorded as a
periodic local field potential. Depletion of cytoplasmic Cl with Cl-free saline
abolished all of the ibotenate-induced effects. Perforated-patch-clamp recording in single PC neurons revealed a spatial difference in the
Cl-dependent periodic depolarizations in the
bursting neurons, with a higher amplitude in the apical region. These
results suggest the involvement of excitatory GluClRs in the
unidirectional propagation of waves in the PC.
Key words:
neural oscillation; wave propagation; olfaction; mollusk; procerebrum; glutamate; ibotenate; perforated patch recording; fluorescent Ca2+ indicator
Copyright © 2003 Society for Neuroscience 0270-6474/03/2372932-07$05.00/0
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