Run-up of gamma-aminobutyric acid(C) responses in catfish retinal cone-horizontal cell axon-terminals is modulated by protein kinase A and C.
Using whole-cell voltage-clamp techniques, we investigated the protein kinase modulation of gamma-aminobutyric acid(C) (GABA(C))-activated currents relating to run-up regulation in dissociated cone-horizontal cell (HC) axon-terminals from catfish retina. GABA induced an inward chloride current in cells voltage-clamped at -70 mV. With repetitive applications of 10 microM GABA, the peaks of the GABA responses increased up to approximately 135% of the control responses during a period of 10 min. Intracellular application of forskolin, an adenylate cyclase activator, decreased the run-up of GABA(C) responses. H8 dihydrochloride, a cAMP inhibitor, enhanced this run-up to 190% of the control responses. 1-oleoyl-2-acetyl-sn-glycerol, a protein kinase C activator, accelerated the run-up of GABA(C) responses. GF 109203X, a PKC inhibitor, decreased the run-up. These results suggest that retinal GABA(C) responses in cone-HC axon-terminals are modulated by both protein kinase A and C.
Jung
C S
CS
Department of Physics, College of Medicine, The Catholic University of Korea, 505 Banpo-dong, Socho-gu, Seoul, South Korea.
Lee
S J
SJ
Paik
S S
SS
Bai
S H
SH
D000262:Adenylyl Cyclases / Q000378:metabolism; D000818:Animals; D002397:Catfishes; D000242:Cyclic AMP / Q000037:antagonists & inhibitors; D017868:Cyclic AMP-Dependent Protein Kinases / Q000502:physiology*; D004789:Enzyme Activation; D066298:In Vitro Techniques; D018408:Patch-Clamp Techniques; D017729:Presynaptic Terminals / Q000502:physiology*; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000502:physiology*; D018079:Receptors, GABA / Q000502:physiology*; D017949:Retinal Cone Photoreceptor Cells / Q000502:physiology* / Q000648:ultrastructure; D005680:gamma-Aminobutyric Acid / Q000494:pharmacology
C087200:GABA-C receptor; D018079:Receptors, GABA; D005680:gamma-Aminobutyric Acid; D000242:Cyclic AMP; D017868:Cyclic AMP-Dependent Protein Kinases; D011493:Protein Kinase C; D000262:Adenylyl Cyclases