title: Long-term potentiation of primary afferent neurotransmission at trigeminal synapses of juvenile rats.
abstract: Primary afferent monosynaptic and polysynaptic excitatory postsynaptic currents (EPSCs) were recorded from brainstem trigeminal neurons by stimulation of the mandibular nerve attached to the brainstem preparation of juvenile rats. A high-frequency conditioning stimulus induced long-term potentiation (LTP) of high-threshold EPSCs in the majority of trigeminal caudal neurons in substantia gelatinosa, where both A- and C-fibres terminate. However, the same conditioning stimulus did not potentiate low-threshold EPSCs in caudal neurons or EPSCs recorded from neurons in the middle part of trigeminal interpolar nucleus, where C-fibres rarely terminate. LTP in caudal neurons could be induced after blocking N-methyl-D-aspartate (NMDA) receptors with D(-)-2-amino-5-phosphonopentanoic acid (D-AP5, 50 microM), after postsynaptic loading of the Ca2+ chelator BAPTA (10 mM), or even after completely blocking excitatory transmission with kynurenic acid during conditioning. However, LTP was blocked by the metabotropic glutamate receptor antagonist (+)-alpha-methyl-4-carboxyphenylglycine (1 mM). We suggest that LTP of the trigeminal primary afferent EPSCs is induced preferentially in the C-fibre inputs and that the induction mechanism involves metabotropic glutamate receptors, possibly at the presynaptic terminals.
authors.affiliation: Department of Neurobiology, Division of Maxillofacial Systems, Graduate School of Dentistry, Tokyo Medical and Dental University, Yushima, Tokyo 113-0034, Japan.
authors.forename: M
authors.initials: M
authors.lastname: Hamba
authors.forename: K
authors.initials: K
authors.lastname: Onodera
authors.forename: T
authors.initials: T
authors.lastname: Takahashi
mesh_terms: D015763:2-Amino-5-phosphonovalerate / Q000494:pharmacology; D000818:Animals; D001565:Benzoates / Q000494:pharmacology; D002614:Chelating Agents / Q000494:pharmacology; D004533:Egtazic Acid / Q000031:analogs & derivatives / Q000494:pharmacology; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology; D019706:Excitatory Postsynaptic Potentials / Q000187:drug effects / Q000502:physiology; D005998:Glycine / Q000031:analogs & derivatives / Q000494:pharmacology; D066298:In Vitro Techniques; D007736:Kynurenic Acid / Q000494:pharmacology; D017774:Long-Term Potentiation / Q000187:drug effects / Q000502:physiology*; D009475:Neurons, Afferent / Q000187:drug effects / Q000502:physiology*; D051381:Rats; D017208:Rats, Wistar; D018094:Receptors, Metabotropic Glutamate / Q000037:antagonists & inhibitors; D016194:Receptors, N-Methyl-D-Aspartate / Q000037:antagonists & inhibitors; D013569:Synapses / Q000187:drug effects / Q000502:physiology*; D009435:Synaptic Transmission / Q000187:drug effects / Q000502:physiology*; D014278:Trigeminal Nuclei / Q000187:drug effects / Q000502:physiology*
chemical_list: D001565:Benzoates; D002614:Chelating Agents; D018691:Excitatory Amino Acid Antagonists; D018094:Receptors, Metabotropic Glutamate; D016194:Receptors, N-Methyl-D-Aspartate; C079694:alpha-methyl-4-carboxyphenylglycine; D004533:Egtazic Acid; D015763:2-Amino-5-phosphonovalerate; D007736:Kynurenic Acid; C025603:1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid; D005998:Glycine