Inhibition of Na+-dependent GABA uptake in isolated frog sensory nerve cell bodies by extra- and intracellular Li

• Published in: Neuroscience letters Vol. 81; no. 3; p. 314
• Main Authors: Tokutomi, N, Ikemoto, Y, Nagasawa, K, Akaike, N
• Format: Journal Article
• Language: English
• Published: Ireland 29.10.1987
• Subjects: Animals; gamma-Aminobutyric Acid - metabolism; Ganglia, Spinal - drug effects; Ganglia, Spinal - metabolism; In Vitro Techniques; Lithium - administration & dosage; Lithium - pharmacology; Membrane Potentials - drug effects; Rana catesbeiana; Sodium - physiology
• ISSN: 0304-3940
• DOI: 10.1016/0304-3940(87)90402-2

The effect of Li+ on the Na+-dependent gamma-aminobutyric acid (GABA) uptake was investigated by examining the effects of external and internal Li+ ([Li]o and [Li]i) on GABA-gated Cl- current (ICl) in the frog dorsal root ganglion cells using the suction pipette technique which allows the internal perfusion under voltage-clamp condition. The suppression of GABA responses in the presence of external Na+ ([Na]o) was larger at lower than at higher GABA concentration. Replacement of [Na]o with Li+ completely removed the Na+ suppression, and GABA dose-response curve in Li+ external solution agreed well with that in Na+-free (Tris+) external solution. Either increasing [Li]i) or internal Na+ ([Na]i) at a constant [Na]o equally reduced the Na+-dependent suppression of GABA-gated ICl. The results indicate that both the [Li]o and [Li]i remove in different manner the [Na]o-dependent suppression of GABA-induced ICl:i.e. the [Li]o acts as a blocker of Na+-GABA co-transport mechanism while the increase of [Li]i decreases the Na+ electrochemical potential gradient across the soma membrane as well as [Na]i does.