title: GABA(B) receptor-mediated presynaptic inhibition of glycinergic transmission onto substantia gelatinosa neurons in the rat spinal cord.
abstract: The GABA(B) receptor-mediated presynaptic inhibition of glycinergic transmission was studied from young rat substantia gelatinosa (SG) neurons using a conventional whole-cell patch clamp technique. Action potential-dependent glycinergic inhibitory postsynaptic currents (IPSCs) were recorded from SG neurons in the presence of 3 mM kynurenic acid and 10 microM SR95531. In these conditions, baclofen (30 microM), a selective GABA(B) receptor agonist, greatly reduced the amplitude of glycinergic IPSCs and increased the paired-pulse ratio. Such effects were completely blocked by 3 microM CGP55845, a selective GABA(B) receptor antagonist, indicating that the activation of presynaptic GABA(B) receptors decreases glycinergic synaptic transmission. Glycinergic IPSCs were largely dependent on Ca2+ influxes passing through presynaptic N- and P/Q-type Ca2+ channels, and these channels contributed equally to the baclofen-induced inhibition of glycinergic IPSCs. However, the baclofen-induced inhibition of glycinergic IPSCs was not affected by either 100 microM SQ22536, an adenylyl cyclase inhibitor, or 1 mM Ba2+, a G-protein coupled inwardly rectifying K+ channel blocker. During the train stimulation (10 pulses at 20 Hz), which caused a marked synaptic depression of glycinergic IPSCs, baclofen at a 30 microM concentration completely blocked glycinergic synaptic depression, but at a 3 microM concentration it largely preserved glycinergic synaptic depression. Such GABA(B) receptor-mediated dynamic changes in short-term synaptic plasticity of glycinergic transmission onto SG neurons might contribute to the central processing of sensory signals.
authors.affiliation: Department of Pharmacology, School of Dentistry, Kyungpook National University, 188-1 Samduk 2 ga-dong, Jung-gu, Daegu 700-412, Republic of Korea Department of Physiology, School of Medicine, Seoul National University, Seoul 110-799, Republic of Korea Department of Pharmacology, School of Medicine, Kyungpook National University, Daegu 700-412, Republic of Korea Brain Science & Engineering Institute, Kyungpook National University, Daegu 700-412, Republic of Korea.
authors.forename: In-Sun
authors.initials: IS
authors.lastname: Choi
authors.forename: Jin-Hwa
authors.initials: JH
authors.lastname: Cho
authors.forename: Seok-Gwon
authors.initials: SG
authors.lastname: Jeong
authors.forename: Jung-Soo
authors.initials: JS
authors.lastname: Hong
authors.forename: Sang-Jung
authors.initials: SJ
authors.lastname: Kim
authors.forename: Jun
authors.initials: J
authors.lastname: Kim
authors.forename: Maan-Gee
authors.initials: MG
authors.lastname: Lee
authors.forename: Byung-Ju
authors.initials: BJ
authors.lastname: Choi
authors.forename: Il-Sung
authors.initials: IS
authors.lastname: Jang
mesh_terms: D000818:Animals; D001418:Baclofen / Q000494:pharmacology; D058786:GABA-B Receptor Agonists; D005998:Glycine / Q000037:antagonists & inhibitors / Q000502:physiology*; D053444:Inhibitory Postsynaptic Potentials / Q000187:drug effects / Q000502:physiology; D009433:Neural Inhibition / Q000187:drug effects / Q000502:physiology*; D009474:Neurons / Q000187:drug effects / Q000502:physiology; D051381:Rats; D017207:Rats, Sprague-Dawley; D018080:Receptors, GABA-B / Q000502:physiology*; D017661:Receptors, Presynaptic / Q000819:agonists / Q000037:antagonists & inhibitors / Q000502:physiology*; D013116:Spinal Cord / Q000187:drug effects / Q000502:physiology; D013376:Substantia Gelatinosa / Q000187:drug effects / Q000502:physiology*; D009435:Synaptic Transmission / Q000187:drug effects / Q000502:physiology*
chemical_list: D058786:GABA-B Receptor Agonists; D018080:Receptors, GABA-B; D017661:Receptors, Presynaptic; D001418:Baclofen; D005998:Glycine