Inhibition of transmitter release and long-term depression in the avian hippocampus.
Long-term depression has recently been shown to occur at glutamatergic synapses in the avian hippocampus and requires activation of calcium/calmodulin-dependent protein kinase II in the nerve terminal. Here using whole cell and intracellular recordings from brain slices, we show that the N-type calcium channel contributes significantly to glutamate release in the avian hippocampus. Activation of the metabotrobic gamma-aminobutyric acid (GABA)(B) receptor by the specific agonist baclofen blocks synaptic transmission. The action of baclofen was associated with a change in paired pulse facilitation indicating that it resulted from a reduction in the probability of transmitter release. In contrast, no change in paired pulse facilitation was observed following the induction of long-term depression. These results show that activation of GABA(B) receptors and long-term depression reduce transmitter release by distinct mechanisms.
Margrie
T W
TW
The Neuroscience Group, Faculty of Medicine and Health Sciences, The University of Newcastle, Callaghan, Australia.
Rostas
J A
JA
Sah
P
P
D000818:Animals; D000831:Animals, Newborn; D001418:Baclofen / Q000494:pharmacology; D020864:Calcium Channels, N-Type / Q000187:drug effects / Q000378:metabolism; D002645:Chickens / Q000033:anatomy & histology* / Q000502:physiology*; D018755:GABA Agonists / Q000494:pharmacology; D006624:Hippocampus / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism*; D066298:In Vitro Techniques; D009433:Neural Inhibition / Q000187:drug effects* / Q000502:physiology*; D009474:Neurons / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D018377:Neurotransmitter Agents / Q000378:metabolism*; D018080:Receptors, GABA-B / Q000187:drug effects / Q000378:metabolism; D009435:Synaptic Transmission / Q000187:drug effects / Q000502:physiology; D013997:Time Factors
D020864:Calcium Channels, N-Type; D018755:GABA Agonists; D018377:Neurotransmitter Agents; D018080:Receptors, GABA-B; D001418:Baclofen