Physiological roles of glycine and gamma-aminobutyric acid in dissociated neurons of rat visual cortex.
The effects of glycine (Gly) and gamma-aminobutyric acid (GABA) on the neurons acutely dissociated from rat visual cortex (VC) were investigated in the whole-cell mode using a conventional patch-clamp technique. GABA and Gly evoked Cl- currents (ICl) in a concentration-dependent manner at a holding potential (VH) of -50 mV. The half maximum effective concentrations (EC50) were 4.64 x 10(-6) M for GABA and 6.67 x 10(-5) M for Gly. Strychnine and bicuculline reversively inhibited both 10(-5) M GABA- and 10(-4) M Gly-induced ICl in a concentration-dependent manner. The half maximum inhibitory concentrations (IC50) of strychnine on GABA- and Gly-induced currents were 4.00 x 10(-6) M and 8.26 x 10(-8) M, respectively. The IC50 values of bicuculline on GABA and Gly responses were 1.18 x 10(-6) M and 2.97 x 10(-4), respectively. GABA at 10(-5) M, which is near the EC50 of the GABA response, induced ICl in all neurons tested (n = 83). However, Gly of 10(-4) M, which is also near the EC50 of the Gly response, induced ICl in 34 out of 83 neurons tested (41%). Moreover, the maximum amplitude of the Gly response was about 60% of that of the GABA response. On the other hand, the enhancement of N-methyl-D-aspartate (NMDA, 3 x 10(-4) M) response by Gly (10(-6) M) was observed in all neurons (n = 36) whether they had the Gly-induced ICl or not.(ABSTRACT TRUNCATED AT 250 WORDS)
Takahashi
Y
Y
Laboratory of Neuroinformation Science, Faculty of Liberal Arts, Tohoku Gakuin University, Sendai, Japan.
Shirasaki
T
T
Yamanaka
H
H
Ishibashi
H
H
Akaike
N
N
D000818:Animals; D001640:Bicuculline / Q000494:pharmacology; D018118:Chloride Channels / Q000187:drug effects / Q000378:metabolism; D004594:Electrophysiology; D018756:GABA Antagonists; D005998:Glycine / Q000037:antagonists & inhibitors / Q000494:pharmacology / Q000502:physiology*; D066298:In Vitro Techniques; D008564:Membrane Potentials / Q000187:drug effects; D016202:N-Methylaspartate / Q000502:physiology; D009474:Neurons / Q000187:drug effects / Q000502:physiology*; D051381:Rats; D017208:Rats, Wistar; D013331:Strychnine / Q000494:pharmacology; D014793:Visual Cortex / Q000166:cytology / Q000502:physiology*; D005680:gamma-Aminobutyric Acid / Q000494:pharmacology / Q000502:physiology*
D018118:Chloride Channels; D018756:GABA Antagonists; D005680:gamma-Aminobutyric Acid; D016202:N-Methylaspartate; D013331:Strychnine; D005998:Glycine; D001640:Bicuculline