title: Participation of excitatory amino acid receptors in the slow excitatory synaptic transmission in the rat spinal dorsal horn in vitro.
abstract: The participation of excitatory amino acid (EAA) receptors in the responses of deep dorsal horn neurons to repetitive stimulation of dorsal roots was investigated using a spinal slice preparation and current-clamp and voltage-clamp techniques. Using EAA receptor and substance P (SP) receptor antagonists and current-clamp, slow excitatory synaptic response evoked by 10-20 Hz stimulation consisted of two depolarizing components: an initial component lasting 1-5 s and a late-one of 1-3 min duration. The initial and late components of the slow excitatory postsynaptic currents (EPSCs) can also be distinguished on the basis of their voltage-dependence and sensitivity to Mg2+ ions, D-2-amino-5-phosphonovalerate (D-APV) and 6-cyano-2,3-dihydroxy-7-nitroquinoxaline (CNQX). In the presence of Mg2+, the initial component of the slow EPSC increased with membrane hyperpolarization, whereas the late component decreased. In a zero-Mg2+ medium, the initial component was potentiated, but the late component was reduced, or unchanged. CNQX reduced the initial component. In a zero-Mg2+ solution, or at membrane potentials positive to -55 mV in 1 mM Mg2+, D-APV reduced or even abolished the initial component, whereas the late component was not modified by D-APV. We propose that slow excitatory synaptic response evoked in deep dorsal horn neurons by repetitive stimulation of primary afferents has two components, an initial transient component that requires activation of N-methyl-D-aspartate (NMDA) and non-NMDA receptors, and a late longer-lasting peptidergic component that has been already described (Brain Res., 290 (1984) 336-341.
authors.affiliation: Department of Veterinary Physiology and Pharmacology, Iowa State University, Ames 50011.
authors.forename: G
authors.initials: G
authors.lastname: Gerber
authors.forename: M
authors.initials: M
authors.lastname: Randić
mesh_terms: D015763:2-Amino-5-phosphonovalerate / Q000494:pharmacology*; D018750:6-Cyano-7-nitroquinoxaline-2,3-dione; D000200:Action Potentials / Q000187:drug effects; D000818:Animals; D004558:Electric Stimulation; D066298:In Vitro Techniques; D011810:Quinoxalines / Q000494:pharmacology*; D051381:Rats; D017459:Receptors, Amino Acid; D011956:Receptors, Cell Surface / Q000502:physiology*; D016194:Receptors, N-Methyl-D-Aspartate; D017981:Receptors, Neurotransmitter / Q000502:physiology*; D013116:Spinal Cord / Q000187:drug effects / Q000502:physiology*
chemical_list: D011810:Quinoxalines; D017459:Receptors, Amino Acid; D011956:Receptors, Cell Surface; D016194:Receptors, N-Methyl-D-Aspartate; D017981:Receptors, Neurotransmitter; D018750:6-Cyano-7-nitroquinoxaline-2,3-dione; D015763:2-Amino-5-phosphonovalerate