Ionotropic GABA receptors with mixed pharmacological properties of GABAA and GABAC receptors.
Ionotropic gamma-aminobutyric acid (GABA) receptors form a large family of molecular isoforms with distinct properties. We have characterized a distinct new type of GABA receptors in CA1 pyramidal cells in rat hippocampal slices. Somatic application of GABA induced currents which were partially suppressed by (1,2,5,6-tetrahydropyridin-4-yl)methylphosphinic acid (TPMPA), a specific antagonist of GABA(C) receptors. This sensitivity was enhanced when we evoked the currents by the GABA(C) receptor agonist cis-4-aminocrotonic acid (CACA). However, both GABA- and CACA-evoked currents were sensitive towards bicuculline and thus lack the defining feature of GABA(C) receptors, which are insensitive towards this antagonist. Spontaneous miniature post-synaptic currents (mIPSCs) revealed a similar pharmacological behaviour. We conclude that juvenile CA1 pyramidal cells express a fraction of ionotropic GABA receptors with mixed pharmacological properties of both, GABA(A) and GABA(C) receptors.
Johannes-Müller-Institut für Physiologie, Universitätsklinikum Charité, Humboldt-Universität Berlin, Tucholskystrasse 2, 10117 Berlin, Germany.
Kristin
K
Hartmann
Frank
F
Stief
Andreas
A
Draguhn
Christiane
C
Frahm
D000818:Animals; D001640:Bicuculline / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D058785:GABA-A Receptor Agonists; D058787:GABA-A Receptor Antagonists; D006624:Hippocampus / Q000187:drug effects / Q000502:physiology; D051381:Rats; D017208:Rats, Wistar; D018079:Receptors, GABA / Q000502:physiology*; D011963:Receptors, GABA-A / Q000502:physiology*; D005680:gamma-Aminobutyric Acid / Q000494:pharmacology
D058785:GABA-A Receptor Agonists; D058787:GABA-A Receptor Antagonists; C087200:GABA-C receptor; D018079:Receptors, GABA; D011963:Receptors, GABA-A; D005680:gamma-Aminobutyric Acid; D001640:Bicuculline