Degeneration argyrophilia as an index of neural maturation: Studies on the optic tract of the golden hamster

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Abstract
The maturation of the retinofugal Systems of the golden hamster has been traced by using the Fink‐Heimer silver technique to stain the degenerating axons and terminal arorizations aferr enucleation at different ages from birth to adulthool. From birth to 12 days of age intense degeneration argyrophilia can only be seen at short (15–36 hours) survival times in the optic tract and its terminal areas. By 72 hours after enucleation virtually all traces of axon degeneration have vanished. Starting at about 14 days of age (time of eye opening) sparse evidence of residual degeneration argyrophilia can be found in strtum opticum and stratum griseum superficiale of the superior colliculus at 72 and even at 240 hours survival. The intensity of the long‐lasting degeneration argyrophilia rapidly increases durin the next two weeks although shortlatency degeneration argyrophiloia does not start decreasing in intensity until 24 days of age.Since Lund and Lund (1972) have found that typicl optic tract synapses are first identifiable in the superior colliculus of the rat at the time of eye opening (12 to 14 days), it is possibnle that the onset of long‐lasting degeneration argyrophilia signals an important structural or functional change in the neuron. Since degeneration methods can be used to trace the maturation of fiber tracts of known origin and trajectory, they may provide a relatively convenient means of identifying periods in which particular fiber Systems are underoing rapid developmental changes.