RETROGRADE TRANSPORT AND INTRANEURONAL FATE OF EXOGENOUS HORSERADISH PEROXIDASE IN THE NERVOUS SYSTEM

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Abstract
Exogenous horseradish peroxidase (HRP, Type VI, Sigma, EC 1.11.1.7) was applied as a marker for retrograde neuroanatomical tracing in the nigroneostriatal system and the sciatic nerve of adult rats. The retrograde transport and intraneuronal fate of HRP was examined with light microscopy and EM. In the nigroneostriatal system, the labeled neurons containing many brown granules in their perikarya were observed in the ipsilateral substantia nigra 3-4 h after an injection of HRP, confirming the existence of a nigroneostriatal pathway. Ultrastructurally, these granules appear as multivesicular and lysosomal bodies in the perinuclear region. The labeled nerve cells of the spinal ganglia were also observed within 12 h after the application of HRP in the sciatic nerve. The HRP positive brown granules had accumulated in the perinuclear region and were rapidly degraded by the lysosomal system disappearing 2 wks after the injection. In instances of long periods of survival, characteristic lysosomal bodies which included crystals, crystalloid and laminar structures were found.