Physiological and Morphological Correlates of Presynaptic Inhibition in Primary Afferents of the Lamprey Spinal Cord

Authors

I. V. Batueva, Russian Academy of Sciences
E. A. Tsvetkov, Russian Academy of Sciences
A. K. Sagatelyan, Yerevan State University
James T. Buchanan, Marquette UniversityFollow
N. Vesselkin, Russian Academy of Sciences
V. Adanina, Russian Academy of Sciences
E. I. Suderevskaya, Russian Academy of Sciences
J. -P Rio, INSERM U106
J. Repérant, INSERM U106

Document Type

Article

Language

eng

Format of Original

13 p.

Publication Date

2-1999

Publisher

Elsevier

Source Publication

Neuroscience

Source ISSN

0306-4522

Abstract

Patch-clamp recordings in a whole-cell mode were performed on dorsal sensory cells enzymatically isolated from the spinal cord of two lamprey species, Ichthyomyzon unicuspis and Lampetra fluviatilis. The voltage-activated currents through calcium channels were analysed. GABA and the specific GABA_B receptor agonist baclofen reduced the peak amplitude of inward Ba²⁺ current, as a robust alternate charge carrier through voltage-dependent Ca²⁺ channels. These effects were dose-dependent and reversible. GABA_B receptor antagonists, 2-hydroxysaclofen and δ-amino-n-valeric acid, blocked the reduction of Ba²⁺ currents by GABA and baclofen, while bicuculline, a GABA_A receptor antagonist, had no blocking action. GABA and baclofen did not modify the dorsal sensory cell membrane conductance, indicating that they did not activate ligand-gated channels. However, GABA, but not baclofen, considerably increased membrane conductance and induced Cl^- currents in isolated multipolar neurons (presumably interneurons and/or motoneurons). These findings suggest that GABA and baclofen action on lamprey dorsal sensory cells is mediated by GABA_B receptors. We concluded that GABA-mediated presynaptic inhibition of lamprey dorsal sensory cell fibers results from GABA_B receptor activation followed by a decrease of inward voltage-activated calcium currents. Appositions of GABA-immunoreactive boutons to horseradish peroxidase-labeled fibers from the dorsal root were observed at the ultrastructural level in the dorsal column using postembedding immunogold cytochemistry. It seems likely that these appositions represent the morphological substrate of dorsal sensory cell fiber presynaptic inhibition. In very rare cases, ultrastructural features were observed which could be interpreted as synaptic specializations between the GABA-immunoreactive boutons and the primary afferent fibers.

The extrasynaptic action of GABA as a basis of presynaptic inhibition of this population of primary afferent neurons is discussed.

Comments

Accepted version. Neuroscience, Vol. 88, No. 3 (February 1999): 975-987. DOI. © 1999 Elsevier. Used with permission.

Recommended Citation

Batueva, I. V.; Tsvetkov, E. A.; Sagatelyan, A. K.; Buchanan, James T.; Vesselkin, N.; Adanina, V.; Suderevskaya, E. I.; Rio, J. -P; and Repérant, J., "Physiological and Morphological Correlates of Presynaptic Inhibition in Primary Afferents of the Lamprey Spinal Cord" (1999). Biological Sciences Faculty Research and Publications. 247.
https://epublications.marquette.edu/bio_fac/247