Immunochemical Characterization of Synaptosomal Membrane Antigens from Chicken Brain : Histochemical Demonstration of Changes in Distribution During Development

The developmental changes in the distribution of a number of nerve specific synaptic membrane antigens have been investigated in a number of tissues using indirect immunofluorescence histochemistry. In all tissues examined, by the time synaptic contacts were made, all regions of tissue that were going to display these antigens had already done so. Areas of tissue rich in actively dividing neuroblasts or postmitotic undifferentiated neurons showed little fluorescence. Characteristic strong fluorescence was only visible where regions of differentiated synapses or axons were present. In the optic nerve, and perhaps also in the white matter of the cerebellum and the outer plexiform layer of the retina, the antigens were already present before synapse formation. After synapse formation the antigens disappeared from the outer plexiform layer of the retina and the white matter of the cerebellum and spinal cord. The amount of fluorescence was drastically reduced in the deep cerebellar nuclei but did not change appreciably in the other areas examined. The loss of these antigens occurred at a different time in each of the tissue areas, indicating that it was related to the maturation of a particular network of neurons rather than the animal as a whole. By considering the pattern of developmental change of this set of antigens, the possibility that some of them may be involved in the processes of intercellular recognition or synaptogenesis has been examined.