Effects of bicuculline application on the somatosensory responses of secondary vestibular neurons

C. Grasso, G. Li Volsi, E. Cataldo, D. Manzoni, M. Barresi
Neuroscience. 2016-10-01; 335: 122-133
DOI: 10.1016/j.neuroscience.2016.08.035

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Grasso C(1), Li Volsi G(1), Cataldo E(2), Manzoni D(3), Barresi M(4).

Author information:
(1)Department of Biomedical and Biotechnological Sciences – Section of Physiology, University of Catania, I-95125 Catania, Italy.
(2)Department of Physics, University of Pisa, I-56127 Pisa, Italy.
(3)Department of Translational Research and New Technologies in Medicine and Surgery, University of Pisa, I-56127 Pisa, Italy.
(4)Department of Drug Sciences, University of Catania, I-95125 Catania, Italy.

Limb somatosensory signals modify the discharge of vestibular neurons and elicit
postural reflexes, which stabilize the body position. The aim of this study was
to investigate the contribution of the γ-amino-butyric-acid (GABA) to the
responsiveness of vestibular neurons to somatosensory inputs. The activity of 128
vestibular units was recorded in anesthetized rats in resting conditions and
during sinusoidal foreleg rotation around the elbow or shoulder joints
(0.026-0.625Hz, 45° peak amplitude). None of the recorded units was influenced by
elbow rotation, while 40% of them responded to shoulder rotation. The selective
GABAA antagonist receptor, bicuculline methiodine (BIC), was applied by
microiontophoresis on single vestibular neurons and the changes in their activity
at rest and during somatosensory stimulation was studied. In about half of cells
the resting activity increased after the BIC application: 75% of these neurons
showed also an increased response to somatosensory inputs whereas 17% exhibited a
decrease. Changes in responsiveness in both directions were detected also in the
units whose resting activity was not influenced by BIC. These data suggest that
the responses of vestibular neurons to somatosensory inputs are modulated by GABA
through a tonic release, which modifies the membrane response to the synaptic
current. It is also possible that a phasic release of GABA occurs during foreleg
rotation, shaping the stimulus-elicited current passing through the membrane. If
this is the case, the changes in the relative position of body segments would
modify the GABA release inducing changes in the vestibular reflexes and in
learning processes that modify their spatio-temporal development.

Copyright © 2016 IBRO. Published by Elsevier Ltd. All rights reserved.

DOI: 10.1016/j.neuroscience.2016.08.035
PMID: 27579770 [Indexed for MEDLINE]

Auteurs Bordeaux Neurocampus