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Glial hyperpolarization upon nerve root stimulation in the leech Hirudo medicinalis
Author(s) -
Schmidt Joachim,
Prinz Petra,
Deitmer Joachim W.
Publication year - 1999
Publication title -
glia
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.954
H-Index - 164
eISSN - 1098-1136
pISSN - 0894-1491
DOI - 10.1002/(sici)1098-1136(199907)27:1<32::aid-glia4>3.0.co;2-9
Subject(s) - hyperpolarization (physics) , cnqx , biology , neuroscience , stimulation , depolarization , membrane potential , neuropil , neuromodulation , glutamate receptor , biophysics , chemistry , ampa receptor , central nervous system , biochemistry , receptor , organic chemistry , nuclear magnetic resonance spectroscopy
Hyperpolarizing responses in neuropil glial cells evoked by nerve root stimulation were studied in the central nervous system of the leech Hirudo medicinalis using intracellular recording and extracellular stimulation techniques. From a mean resting potential of −60.5 ± 1.0, the glial membrane was hyperpolarized by −8.6 ± 0.8 mV, via stimulation of the dorsal posterior nerve root in an isolated ganglion. Nerve root stimulation evoked biphasic or depolarizing responses in glial cells with resting potentials around −70 mV (Rose CR, Deitmer JW. J. Neurophysiol. 73:125–131, 1995). The hyperpolarizing response was reduced by the ionotropic glutamate receptor antagonist CNQX (50 μM) to 58% of its initial amplitude. In 15 mM Ca 2+ /15 mM Mg 2+ ‐saline the hyperpolarization was reduced by 44%. The hyperpolarization that persisted in high‐divalent cation saline was not affected by CNQX. Bath‐applied glutamate (500 μM) and kainate (2 μM) elicited glial hyperpolarizations that were sensitive to CNQX and 10 mM Mg 2+ /1 mM Ca 2+ ‐saline. The 5‐HT‐antagonist methysergide did not affect the hyperpolarizations evoked by nerve root stimulation. The results show that in the leech glial membrane responses to neuronal activity include not only depolarizations, as shown previously, but also hyperpolarizations, which are mediated by direct and indirect neuron–glial communication pathways. In the indirect pathway, glutamate is a transmitter between neurons. GLIA 27:32–38, 1999. © 1999 Wiley‐Liss, Inc.