Eye nerve success with blind tadpoles

A blind tadpole, with an eye grafted to its tail.
Credit: Allen Discovery Centre, Tufts University

A common migraine medication shows promise for promoting nerve growth to transplanted or regenerated body parts, new research shows.

A team of researchers from the Allen Discovery Centre at Tufts University in Massachusetts, US, tested Zolmitriptan, a selective serotonin receptor agonist, for its ability to stimulate integration and function of transplanted organs.

In an experiment that carries faint shades of the The Island of Doctor Moreau, Douglas Blackiston and colleagues grafted eyes into the tails of blind tadpoles. After the researchers administered Zolmitriptan the tadpoles developed a significantly better ability to distinguish colour and movement than untreated controls.

The team tested responses and reactions in four tadpole cohorts: sighted and blind ones, and those with tail-grafted eyes, treated and untreated.

In one experiment, the researchers set up red and blue zones for the infant frogs, and encouraged them to favour the blue one. Just over three-quarters of sighted tadpoles passed the test, while only 3% of the blind ones managed it.

Among those with grafted eyes, 11% of the untreated cohort avoided the red zones, but the number rose to 29% among those taking the migraine meds.

A second test tracked responses to movement, with the tadpoles exposed to a slowly revolving circle of lights beneath their tank. Some 82% of the sighted animals followed the pattern, as did 38% of the blind ones and 32% of those with untreated eye grafts. An impressive 57% of the treated tadpoles achieved the feat.

The results demonstrated that Zolmitriptan strongly influences the growth and connection of nerves between grafted organs and host nervous systems, suggesting a way forward for regenerative medicine.

The migraine medication works as a neurotransmitter, and Blackiston’s team provides a proof of concept that existing drugs in this class can be repurposed to improve success rates in organ transplants.

The work also paves the way for further research in the field of brain-body plasticity.

“The fact that the grafted eyes in our model system could transmit visual information, even when direct connections to the brain were absent, suggests the central nervous system contains a remarkable ability to adapt to changes both in function and connectivity,” says Blackiston.

The study is published in the journal npj Regenerative Medicine.

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