title: Protein kinase A and C signaling induces bilirubin potentiation of GABA/glycinergic synaptic transmission in rat ventral cochlear nucleus neurons.
abstract: Previous studies have suggested that bilirubin can potentiate GABA/glycinergic synaptic transmission in lateral superior olivary nucleus neurons, but the cellular mechanism has not been defined. The present study evaluated the possible roles of protein kinase A (PKA) and C (PKC) in bilirubin potentiation of GABA/glycinergic synaptic transmission in rat ventral cochlear nucleus (VCN) neurons. VCN neurons were acutely isolated from postnatal 10-12-day-old (P10-12) rats and were voltage-clamped in whole-cell mode. Miniature inhibitory postsynaptic currents (mIPSC) frequencies, but not amplitude, were increased by bilirubin. Forskolin (PKA activator) and H-89 (PKA inhibitor) also individually increased mIPSCs frequency, with an additional increase induced by co-incubation with bilirubin and H-89. Pretreatment with forskolin blocked bilirubin potentiation. mIPSC frequency was not altered by phorbol 12,13-diacetate (PKC activator), but mIPSC frequency was increased following co-application of bilirubin. The mIPSC frequency was increased by chelerythrine (PKC inhibitor), and then further increased after the addition of bilirubin. Neither H-89, forskolin, nor PDA, nor their co-application with bilirubin affected mIPSC amplitudes of GABA-activated (I(GABA))/glycine-activated (I(gly)) currents, suggesting a presynaptic locus of activity. Chelerythrine decreased the mIPSC amplitudes and I(GABA)/I(gly), suggesting a postsynaptic locus of activity. These data suggest that both PKA and PKC can modulate GABA and glycine release in rat VCN neurons. Bilirubin facilitates transmitter release via presynaptic PKA activation, which might provide insight into the cellular mechanism underlying bilirubin-induced hearing dysfunction.
authors.affiliation: Department of Otorhinolaryngology, Affiliated Sixth People's Hospital of Shanghai Jiaotong University, 600 Yishan Road, Shanghai 200233, China.
authors.forename: Chun-Yan
authors.initials: CY
authors.lastname: Li
authors.forename: Hai-Bo
authors.initials: HB
authors.lastname: Shi
authors.forename: Zheng-Nong
authors.initials: ZN
authors.lastname: Chen
authors.forename: Hai-Bo
authors.initials: HB
authors.lastname: Ye
authors.forename: Ning-Ying
authors.initials: NY
authors.lastname: Song
authors.forename: Shan-Kai
authors.initials: SK
authors.lastname: Yin
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D000975:Antioxidants / Q000494:pharmacology; D053119:Benzophenanthridines / Q000494:pharmacology; D001663:Bilirubin / Q000494:pharmacology*; D017626:Cochlear Nucleus / Q000166:cytology*; D005576:Colforsin / Q000494:pharmacology; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism*; D004789:Enzyme Activation / Q000187:drug effects; D005998:Glycine / Q000378:metabolism; D066298:In Vitro Techniques; D007546:Isoquinolines / Q000494:pharmacology; D009433:Neural Inhibition / Q000187:drug effects; D009474:Neurons / Q000187:drug effects*; D018408:Patch-Clamp Techniques / Q000379:methods; D010703:Phorbol Esters / Q000494:pharmacology; D011493:Protein Kinase C / Q000378:metabolism*; D051381:Rats; D015398:Signal Transduction / Q000187:drug effects*; D013449:Sulfonamides / Q000494:pharmacology; D009435:Synaptic Transmission / Q000187:drug effects*; D005680:gamma-Aminobutyric Acid / Q000378:metabolism
chemical_list: D000975:Antioxidants; D053119:Benzophenanthridines; D007546:Isoquinolines; D010703:Phorbol Esters; D013449:Sulfonamides; D005576:Colforsin; C008874:phorbol-12,13-diacetate; D005680:gamma-Aminobutyric Acid; C016299:chelerythrine; D017868:Cyclic AMP-Dependent Protein Kinases; D011493:Protein Kinase C; C063509:N-(2-(4-bromocinnamylamino)ethyl)-5-isoquinolinesulfonamide; D001663:Bilirubin; D005998:Glycine