Synaptic contribution of Ca2+-permeable and Ca2+-impermeable AMPA receptors on isolated carp retinal horizontal cells and their modulation by Zn2+.
Ca(2+)-permeable and Ca(2+)-impermeable AMPA receptors are co-expressed on carp retinal horizontal cells. In the present study, we examined the synaptic contribution and Zn(2+) modulatory effect of these two AMPA receptor subtypes using whole-cell patch clamp technique. Specific Ca(2+)-permeable AMPA receptor antagonist (1-naphthyl acetyl spermine, NAS) and selective Ca(2+)-impermeable AMPA receptor blocker (pentobarbital, PB) were used to separate the glutamate-response in isolated H1 horizontal cell mediated by these two subtypes of AMPA receptors respectively. Application of 100 microM NAS substantially suppressed the current elicited by 3 mM glutamate and the remaining NAS-insensitive component was completely blocked by application of 100 microM PB. In addition, Zn(2+) had dual effects on Ca(2+)-permeable AMPA receptor-mediated current: at low concentration (10 microM), Zn(2+) potentiated the current, but at higher concentrations (100 and 1000 microM), Zn(2+) reduced the current in a dose-dependent manner. However, Zn(2+) (10, 100 and 1000 microM) failed to modulate the NAS-insensitive current mediated by Ca(2+)-impermeable AMPA receptors. Overall, our results suggest that Ca(2+)-permeable AMPA receptors contribute more to the cell's glutamate-response than Ca(2+)-impermeable AMPA receptors. Furthermore, Zn(2+) has dual effects on the Ca(2+)-permeable AMPA receptor activity without affecting Ca(2+)-impermeable AMPA receptors.
Sun
Yan
Y
School of Life Sciences and Biotechnology, Shanghai Jiao Tong University, 800 Dong-Chuan Road, Shanghai 200240, China.
Jiang
Xiao-Dong
XD
Liu
Xue
X
Gong
Hai-Qing
HQ
Liang
Pei-Ji
PJ
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002347:Carps; D002478:Cells, Cultured; D004305:Dose-Response Relationship, Drug; D018698:Glutamic Acid / Q000378:metabolism; D007608:Kainic Acid / Q000378:metabolism; D008564:Membrane Potentials / Q000187:drug effects; D018377:Neurotransmitter Agents / Q000008:administration & dosage / Q000494:pharmacology; D018408:Patch-Clamp Techniques; D010424:Pentobarbital / Q000494:pharmacology; D018091:Receptors, AMPA / Q000037:antagonists & inhibitors / Q000378:metabolism*; D051248:Retinal Horizontal Cells / Q000187:drug effects / Q000502:physiology*; D013096:Spermine / Q000008:administration & dosage / Q000031:analogs & derivatives / Q000494:pharmacology; D013569:Synapses / Q000187:drug effects / Q000502:physiology*; D015032:Zinc / Q000378:metabolism*
D018377:Neurotransmitter Agents; D018091:Receptors, AMPA; C067506:1-naphthylacetylspermine; D013096:Spermine; D018698:Glutamic Acid; D010424:Pentobarbital; D015032:Zinc; D007608:Kainic Acid; D002118:Calcium