Abstract
Purpose: :
To understand the mechanisms of spontaneous retinal waves, particularly those mediated by glutamatergic transmission (stage III waves), we examined both electrical and Ca2+ activities in various types of cells in mouse and rabbit retinas.
Methods: :
Single and dual patch-clamp recordings were made from wholemount postnatal mouse and rabbit retinas, in conjunction with Ca2+ imaging from individual neurons transfected with the Ca2+-indicator protein GCaMP3.
Results: :
Cells in the inner nuclear layer (INL) were individually identified after transfection of GCaMP3. Ca2+ imaging revealed spontaneous Ca2+ transients in ON bipolar cell axon terminals. Simultaneous Ca2+ imaging and patch-clamp recording from neurons in the ganglion cell layer (GCL) an INL showed that the spontaneous Ca2+ activities in bipolar cells were correlated with retinal waves in the GCL. Patch-clamp recordings from bipolar cells in the wholemount retina further demonstrated bursting activities and excitatory synaptic inputs during stage III waves. Blocking inhibitory synaptic transmission with picrotoxin and strychnine increased the frequency and synchrony of both wave-related electrical bursts and Ca2+ activities in INL and GCL neurons.
Conclusions: :
Patch-clamp recording and Ca2+ imaging from targeted neurons in the INL of the wholemount retina provided direct evidence for the participation of bipolar cells in stage III retinal waves and for the presence of synaptic inputs to these cells during retinal waves.
Keywords: retinal development • bipolar cells • amacrine cells