TY - JOUR T1 - Modulation of Presynaptic Calcium Transients by Metabotropic Glutamate Receptor Activation: A Differential Role in Acute Depression of Synaptic Transmission and Long-Term Depression JF - The Journal of Neuroscience JO - J. Neurosci. SP - 6885 LP - 6890 DO - 10.1523/JNEUROSCI.22-16-06885.2002 VL - 22 IS - 16 AU - Guido C. Faas AU - Hita Adwanikar AU - Robert W. Gereau IV AU - Peter Saggau Y1 - 2002/08/15 UR - http://www.jneurosci.org/content/22/16/6885.abstract N2 - Activation of group I metabotropic glutamate receptors (mGluRs) can induce acute depression of excitatory synaptic transmission and long-term depression (LTD) in area CA1 of the rat hippocampus. The underlying mechanisms for both forms of depression are unknown. By measuring presynaptic calcium transients, we show that a reduction in the stimulation-induced presynaptic calcium rise that triggers vesicular release causes the acute depression of transmission by group I mGluRs. In contrast, the mechanism underlying mGluR-induced LTD does not involve a persistent change in stimulation-induced calcium influx. However, analysis of paired-pulse facilitation experiments suggests a presynaptic location for expression of this form of LTD. Furthermore, we show that mGluR-induced LTD can be completely blocked by a specific mGluR5 antagonist, whereas mGluR1 antagonists strongly attenuate the acute depression of transmission. These results support the hypothesis that the acute depression of transmission caused by activation of group I mGluRs involves regulation of stimulation-induced presynaptic calcium transients, whereas mGluR-induced LTD involves a distinct presynaptic modulation downstream of calcium influx. ER -