Funnel in the eye: Signal focusing increases photos...( mbines the individual electrical impuls...)

If there is sufficient light the signal focus is deactivated. This is triggered off by dopamine. As Klaus Willecke, a professor of genetics at the University of Bonn, explains, 'dopamine is formed by the retina when the retina is hit by light. Dopamine activates a cascade of signals which eventually results in the closure of a particular channel in the amacrine II cells called connexin36.' The research team also seems to have found the right cork for connexin36, abbreviated to 'Cx36'. Professor Willecke says that 'apparently, under the influence of dopamine, a phosphate group is bound to Cx36 and inhibits the channel.' It is the first time that direct proof has been available that this mechanism exists.

The importance of signal focusing is demonstrated by mice which cannot produce Cx36. Their amacrine II cells cannot combine to form networks when necessary. The consequences for these nocturnal rodents are devastating. Klaus Willecke says that their rod vision is extremely impeded, so that their visual perception is very limited in poor light.

Protein kinase A mediated phosphorylation of connexin36 in mouse retina results in decreased gap junctional communication between AII amacrine cells.