GABA(B)-receptor modulation of short-term synaptic depression at an excitatory input to murine hippocampal CA3 pyramidal neurons.
GABA(B) agonists inhibit excitatory transmission to hippocampal CA3 neurons during low frequency stimulation. We examined whether GABA(B) receptor activation can also enhance synaptic efficacy, when investigated at an input with high initial release probability. Short-term depression of field excitatory postsynaptic potential (EPSP) amplitude was observed during trains of stimuli applied to associational/commissural inputs (10-50 Hz; 22 degrees C). Baclofen (10 microM) reduced the amplitude of initial EPSPs in a train, and also reduced the degree of short-term depression. EPSPs recorded late in a train were significantly larger in baclofen than those recorded in control solution. These dual effects were mimicked by another selective GABA(B) agonist (SKF 97541, 10 microM), and abolished by a GABA(B)-selective antagonist (SCH 50911, 20 microM). The effects of baclofen were similar at a higher recording temperature (32 degrees C), where short-term depression was observed at higher stimulation frequencies. These results are consistent with the idea that a reduction of transmitter release probability could increase the fidelity of high-frequency transmission at this input, an effect that could help account for excitatory effects of GABA(B) agonists in some seizure models.
Hoskison
M M
MM
Department of Neurosciences, University of New Mexico School of Medicine, MSC08 4740, 1 University of New Mexico, Albuquerque, NM 87131-0001, USA.
Connor
J A
JA
Shuttleworth
C W
CW
D000818:Animals; D004558:Electric Stimulation; D019706:Excitatory Postsynaptic Potentials / Q000187:drug effects / Q000502:physiology; D018755:GABA Agonists / Q000494:pharmacology; D018756:GABA Antagonists / Q000494:pharmacology; D008297:Male; D051379:Mice; D008839:Microelectrodes; D009434:Neural Pathways / Q000187:drug effects / Q000502:physiology*; D009924:Organ Culture Techniques; D017966:Pyramidal Cells / Q000187:drug effects / Q000502:physiology*; D018080:Receptors, GABA-B / Q000187:drug effects / Q000378:metabolism*; D009435:Synaptic Transmission / Q000187:drug effects / Q000502:physiology*
D018755:GABA Agonists; D018756:GABA Antagonists; D018080:Receptors, GABA-B