title: Synaptic inputs to granule cells of the dorsal cochlear nucleus.
abstract: The mammalian dorsal cochlear nucleus (DCN) integrates auditory nerve input with nonauditory signals via a cerebellar-like granule cell circuit. Although granule cells carry nonauditory information to the DCN, almost nothing is known about their physiology. Here we describe electrophysiological features of synaptic inputs to granule cells in the DCN by in vitro patch-clamp recordings from P12 to P22 rats. Granule cells ranged from 6 to 8 microm in cell body diameter and had high-input resistance. Excitatory postsynaptic currents consisted of both AMPA receptor-mediated and N-methyl-D-aspartate receptor-mediated currents. Synaptically evoked excitatory postsynaptic currents ranged from -25 to -140 pA with fast decay time constants. Synaptic stimulation evoked both short- and long-latency synaptic responses that summated to spike threshold, indicating the presence of a polysynaptic excitatory pathway in the granule cell circuit. Synaptically evoked inhibitory postsynaptic currents in Cl(-)-loaded cells ranged from -30 to -1,021 pA and were mediated by glycine and, to a lesser extent, GABA(A) receptors. Unlike cerebellar granule cells, DCN granule cells lacked tonic inhibition by GABA. The glycinergic synaptic conductance was mediated by heteromeric glycine receptors and was far stronger than the glutamatergic conductance, suggesting that glycinergic neurons may act to gate nonauditory signals in the DCN.
authors.affiliation: Oregon Hearing Research Center and Vollum Institute, L335A, 3181 S. W. Sam Jackson Park Rd., Portland, OR 97239, USA.
authors.forename: Veeramuthu
authors.initials: V
authors.lastname: Balakrishnan
authors.forename: Laurence O
authors.initials: LO
authors.lastname: Trussell
mesh_terms: D000818:Animals; D001306:Auditory Pathways / Q000166:cytology / Q000187:drug effects / Q000502:physiology; D001307:Auditory Perception / Q000187:drug effects / Q000502:physiology*; D048429:Cell Size; D017626:Cochlear Nucleus / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology; D019706:Excitatory Postsynaptic Potentials / Q000187:drug effects / Q000502:physiology; D018756:GABA Antagonists / Q000494:pharmacology; D005998:Glycine / Q000378:metabolism; D006834:Hydrazines; D053444:Inhibitory Postsynaptic Potentials / Q000187:drug effects / Q000502:physiology; D009433:Neural Inhibition / Q000187:drug effects / Q000502:physiology; D009474:Neurons / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D009924:Organ Culture Techniques; D018408:Patch-Clamp Techniques; D051381:Rats; D017208:Rats, Wistar; D011930:Reaction Time / Q000187:drug effects / Q000502:physiology; D018091:Receptors, AMPA / Q000187:drug effects / Q000502:physiology; D016194:Receptors, N-Methyl-D-Aspartate / Q000187:drug effects / Q000502:physiology; D013194:Staining and Labeling; D013569:Synapses / Q000187:drug effects / Q000502:physiology* / Q000648:ultrastructure; D009435:Synaptic Transmission / Q000187:drug effects / Q000502:physiology*; D005680:gamma-Aminobutyric Acid / Q000378:metabolism
chemical_list: C417561:Alexa 488 hydrazide; D018691:Excitatory Amino Acid Antagonists; D018756:GABA Antagonists; D006834:Hydrazines; D018091:Receptors, AMPA; D016194:Receptors, N-Methyl-D-Aspartate; D005680:gamma-Aminobutyric Acid; D005998:Glycine