SUBCELLULAR-LOCALIZATION OF LOW-AFFINITY NERVE GROWTH-FACTOR RECEPTOR-IMMUNOREACTIVE PROTEIN IN ADULT-RAT PURKINJE-CELLS FOLLOWING TRAUMATIC INJURY

Cerebellar Purkinje cells in the rat express low-affinity nerve growth factor receptor (p75 NGFR) antigen during development, but rarely in normal adult animals. In striking contrast, re-expression of p75 NGFR- immunoreactive protein was reported by light microscopy immunocytochem istry in adult rat Purkinje cells as early as I day after traumatic ax otomy. Characteristically, varicose axons through the infraganglionic zone were also stained. To date, however, there is no information on t he subcellular location of the antigenic re-expression. To address thi s, a pre-embedding immunocytochemical ultrastructural study using affi nity-purified monoclonal 192-IgG was carried out after an experimental ly induced traumatic lesion of the rat cerebellum. At the electron mic roscopic level, immunostaining was intense in Purkinje cells. In these cells, the immunoreactivity was always associated with the internal f ace of the membranes of the rough endoplasmic reticulum, Golgi apparat us and nuclear envelope. Patches of immunoreactivity were also associa ted with the outer surface of the plasma membrane of the cell body, de ndritic processes and axons. It is noteworthy that receptor immunoreac tivity was detected in recurrent collaterals of Purkinje cell axons fo rming symmetric synaptic contacts with the cell body and dendrites of immunonegative local circuit neurons. Results of this study show that injury-induced re-expression of p75 NGFR antigen is restricted to Purk inje cells. Also, the relative importance of the contribution of the l ocal circuit neurons to the production of neurotrophic substances afte r trauma is suggested.