of the microscopes were set up as pre\iiously de-

ssted of synthetc peptide conjugated to bovine thy-rogobuin with the use of gutaradehyde. The antiser-um recognized a protein band of 80 to 90 kD on protein immunoblots of membranes prepared from cells transfected with the rat SPR [S. R. Vigna eta/.,J. Neurosci 14. 834 (1994)j.The cells could be immu-nostained with the antiserum, and the staning could be blocked by preabsorbing the antiserum with SPR,-,. After the incubation w th the primary an-tbody, the tissue sections were washed for 30 min at 22°C in PBS (pH 7.41 and then incubated in the sec-ondary antibody solution (pH7.4) for 2 hours at 22% This secondary antibody solution was identical to the primary antibody solution, except that cyanine (Cy3)-conjugated donkey anti-rabbit ~mmunoglobulinG (no. 711-165-152;Jackson ImmunoResearch Labs.West Grove PA)was present (at a concentration of 1:600) instead of the SPR antibody. Finally. the tissue sec-tions were washed for 20 min in PBS (pH 7.4. 22'Ci, mounted on gelatin-coated sdes, and coverspped with PBS-glycerine containing 1.0%p-phenyeneda-mine to reduce photobeaching. 12. To examine the sites of internalization within the cell, sections were examined w ~ than MRC-600 Confoca