Development of light response and GABAergic excitation-to-inhibition switch in zebrafish retinal ganglion cells.
The zebrafish retina has been an important model for studying morphological development of neural circuits in vivo. However, its functional development is not yet well understood. To investigate the functional development of zebrafish retina, we developed an in vivo patch-clamp whole-cell recording technique in intact zebrafish larvae. We first examined the developmental profile of light-evoked responses (LERs) in retinal ganglion cells (RGCs) from 2 to 9 days post-fertilization (dpf). Unstable LERs were first observed at 2.5 dpf. By 4 dpf, RGCs exhibited reliable light responses. As the GABAergic system is critical for retinal development, we then performed in vivo gramicidin perforated-patch whole-cell recording to characterize the developmental change of GABAergic action in RGCs. The reversal potential of GABA-induced currents (E(GABA)) in RGCs gradually shifted from depolarized to hyperpolarized levels during 2-4 dpf and the excitation-to-inhibition (E-I) switch of GABAergic action occurred at around 2.5 dpf when RGCs became light sensitive. Meanwhile, GABAergic transmission upstream to RGCs also became inhibitory by 2.5 dpf. Furthermore, down-regulation of the K(+)/Cl() co-transporter (KCC2) by the morpholino oligonucleotide-based knockdown approach, which shifted RGC E(GABA) towards a more depolarized level and thus delayed the E-I switch by one day, postponed the appearance of RGC LERs by one day. In addition, RGCs exhibited correlated giant inward current (GICs) during 2.5-3.5 dpf. The period of GICs was shifted to 3-4.5 dpf by KCC2 knockdown. Taken together, the GABAergic E-I switch occurs coincidently with the emergence of light responses and GICs in zebrafish RGCs, and may contribute to the functional development of retinal circuits.
Zhang
Rong-wei
RW
Institute of Neuroscience and State Key Laboratory of Neuroscience, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, 320 Yue-yang Road, Shanghai 200031, China.
Wei
Hong-ping
HP
Xia
Yi-meng
YM
Du
Jiu-lin
JL
D000818:Animals; D015536:Down-Regulation / Q000187:drug effects; D006096:Gramicidin / Q000494:pharmacology; D007814:Larva / Q000187:drug effects / Q000254:growth & development / Q000528:radiation effects; D008027:Light; D009025:Morpholines / Q000494:pharmacology; D009841:Oligonucleotides / Q000494:pharmacology; D018079:Receptors, GABA / Q000502:physiology; D012160:Retina / Q000187:drug effects / Q000254:growth & development* / Q000528:radiation effects*; D012165:Retinal Ganglion Cells / Q000187:drug effects / Q000502:physiology* / Q000528:radiation effects; D027981:Symporters / Q000502:physiology; D015027:Zebrafish / Q000254:growth & development*; D005680:gamma-Aminobutyric Acid / Q000494:pharmacology / Q000502:physiology*; D000096922:K Cl- Cotransporters
D006096:Gramicidin; D009025:Morpholines; D009841:Oligonucleotides; D018079:Receptors, GABA; D027981:Symporters; D005680:gamma-Aminobutyric Acid; D000096922:K Cl- Cotransporters