GABA and baclofen reduce changes in extracellular free calcium in area CA1 of rat hippocampal slices.
Reductions in extracellular free Ca2+-concentration [( Ca2+]o) result from neuronal activation and can be induced by repetitive electrical stimulation or by application of excitatory amino acids. They reflect Ca2+-movements along its electrochemical gradient into pre- and postsynaptic elements. Amino acid-induced reductions in [Ca2+]o are predominantly caused by postsynaptic Ca2+ entry. Under conditions of blocked chemical synaptic transmission, a presynaptic component of extracellular Ca2+ loss becomes apparent during stimulation of the Schaffer collateral/commissural fibers system in stratum radiatum/moleculare. GABA, both iontophoretically and bath applied, always reduces pre- and postsynaptic components of [Ca2+]o changes. Baclofen regularly affects postsynaptic Ca2+ entry and has frequently also a suppressant action on presynaptic Ca2+ entry in area CA1.
D000818:Animals; D001418:Baclofen / Q000494:pharmacology*; D046508:Culture Techniques; D004305:Dose-Response Relationship, Drug; D005110:Extracellular Space / Q000187:drug effects*; D006624:Hippocampus / Q000187:drug effects*; D007473:Ion Channels / Q000187:drug effects*; D008564:Membrane Potentials / Q000187:drug effects; D009474:Neurons / Q000187:drug effects; D051381:Rats; D013569:Synapses / Q000187:drug effects; D005680:gamma-Aminobutyric Acid / Q000494:pharmacology*
D007473:Ion Channels; D005680:gamma-Aminobutyric Acid; D001418:Baclofen