Presynaptic group III mGluR modulation of short-term plasticity in the lateral perforant path of the dentate gyrus in vitro.
Modulation of short-term plasticity by activation of group III metabotropic glutamate receptors (mGluR) was investigated in the lateral perforant path of the dentate gyrus of the rat hippocampus in vitro. Brief trains of stimulation (10 stimuli at 1-100 Hz) evoked short-term depression of field excitatory postsynaptic potentials (EPSPs), with a steady-state level of short-term depression being attained after approximately 5 stimuli. The steady-state level of depression was frequency-dependent, increasing linearly between 1 and 200 Hz. The curve relating transmitter release per unit time to frequency of stimulation increased linearly up to a limiting frequency of 20-50 Hz, and then flattened at higher frequencies. Activation of group III mGluR by the selective agonist L-(+)-2-amino-4-phosphonobutyric acid (L-AP4) had two distinct actions. Firstly, the test EPSP evoked at low test frequencies was inhibited, and secondly, short-term depression evoked at high frequencies was reduced in a frequency and agonist concentration-dependent manner. Short-term facilitation became prominent at high stimulation frequencies as short-term depression was inhibited by activation of group III mGluR. Activation of group III mGluR also shifted the limiting frequency to higher values.
D000818:Animals; D018891:Dentate Gyrus / Q000502:physiology*; D004558:Electric Stimulation; D018690:Excitatory Amino Acid Agonists / Q000494:pharmacology; D019706:Excitatory Postsynaptic Potentials / Q000187:drug effects / Q000502:physiology; D066298:In Vitro Techniques; D009473:Neuronal Plasticity / Q000502:physiology*; D019580:Perforant Pathway / Q000502:physiology*; D011422:Propionates / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D018094:Receptors, Metabotropic Glutamate / Q000378:metabolism*; D017661:Receptors, Presynaptic / Q000378:metabolism; D009435:Synaptic Transmission / Q000187:drug effects / Q000502:physiology
C114785:2-amino-4-phosphono-propinate; D018690:Excitatory Amino Acid Agonists; D011422:Propionates; D018094:Receptors, Metabotropic Glutamate; D017661:Receptors, Presynaptic; C102718:metabotropic glutamate receptor 3