Abstract
Purpose: :
Retinal ganglion cells provide the retinal output signal to the brain and a readout of the retinal information processing. Multielectrode array is a new way to obtain simultaneous recording of many retinal ganglion cells. We therefore applied this technique to investigate the ON–pathways in different mutated mice.
Methods: :
The retina was isolated in Ames’ medium at 37°C and introduced in the recording chamber. It was covered with a piece of nitrocellulose membrane and ring with nylon threads to press it onto the recording electrodes. The MEA60 multielectrode setup was a purchased from Multichannel Systems.
Results: :
Stable recordings of action potentials in up to 40 retinal ganglion cells could be simultaneously monitored with a good signal/noise ratio for over 6 hours. In wild type animals, retinal ganglion cells displayed different patterns of spontaneous activity typically encountered in other brain areas, ranging from an irregular spiking to bursting activity; the firing rates ranged from 0.05 to 30 Hz. In young animals (<4 weeks), synchronous waves of spikes were prevailing. Dark–adaptation (1 h) often increased the spike frequency in a number of retinal ganglion cells. Light stimulation evoked the typical ON, OFF and ON–OFF responses which were modulated by light intensity. Cross–correlation analysis of spontaneous activity and evoked responses revealed different types of interrelations between neighbouring retinal ganglion cells, predominantly synchronous firings due to the shared input activation. Bath application of excitatory or inhibitory neurotransmitters (glutamate, GABA) or their agonists/antagonists reversibly induced typical changes in the firing rates of retinal ganglion cells. In photopic conditions, application of metabotropic group III glutamate receptor agonist, L–AP4 (5 – 40 µM), selectively blocked ON component of the ON–OFF light responses in ganglion cells. In scotopic conditions, L–AP4 abolished both ON and OFF components.
Conclusions: :
These results indicate that the classic physiological responses can be recorded simultaneously in the large population of retinal ganglion cells in the mammalian ex vivo retina. They provide new data on the physiology and pharmacology of retinal information processing. This technique therefore offers a valuable approach to investigate retinal information processing in both wild type and mutated animals.
Keywords: electrophysiology: non-clinical • ganglion cells • signal transduction: pharmacology/physiology