Biochemical studies of transneuronal degeneration: The effects of enucleation on the biochemical maturation of the chick optic tectum

The chick visual system is a useful model to study the biochemical consequences of transsynaptic degeneration. Following enucleation on the day of hatching, the deafferented chick optic tectum at days 12-16 fails to demonstrate the increased protein, glycoprotein and ganglioside content of normal optic tectum. Morphologic and biochemical studies suggest that the number of neurons and glia are not decreased in the deafferented optic tectum. However their surface membrane and intracellular constituents are decreased. Although enucleation produces a marked reduction in total ganglioside and fucosyl glycopeptide constituents, it does not alter the normal developmental changes in the profile of specific gangliosides or in the molecular weight of fucosyl glycopeptides. Within the limits of sensitivity of techniques employed, the effects of transneuronal degeneration on gangliosides and fucosyl glycopeptides appear to be primarily quantitative rather than qualitative. Once synapses are formed presynaptic terminals from the retina may have less effect on the types of gangliosides and the molecular weights of fucosyl glycopeptides than on the amounts of these constituents.