Scientists have discovered a chemical in the zebra fish brain that helps reveal how it regrows its retina, a finding that can potentially cure blindness in humans.

The findings showed that the levels of GABA (gamma aminobutyric acid), a neurotransmitter, best known for its role of calming nervous activity -- drop when the unique self repair process kicks in.

Thus, blocking the chemical (GABA) could lead to new treatments for AMD (age related macular degeneration), the most common cause of blindness and and retinitis pigmentosa.

The structure of the retinas (the light sensing tissue at the back of the eye) of fish and mammals are basically the same and a reduction in GABA might be the trigger for retinal regeneration, the researchers said.

"Our theory is that a drop in GABA concentration is the trigger for regeneration," said James Patton, Professor at Vanderbilt University, in Tennessee, US.

"If we are correct, then it might be possible to stimulate human retinas to repair themselves by treating them with a GABA inhibitor," Patton added.

In the study, when the scientists injected drugs that kept GABA concentrations in the retinas of newly blinded fish at a high level, they found it suppressed the regeneration process.

After injecting an enzyme that lowers GABA levels in normal fish, they found that the Muller glia (retinal cells) began changing and proliferating, the first stage in the regeneration process.

The Muller glia (which in fish play a key role in regeneration) is a special type of adult stem cell.

When regeneration is triggered in zebrafish, the Muller glia begins proliferating and then differentiating into replacements for the damaged nerve cells.