Cholecystokinin in feline vagal and sciatic nerves: concentration, molecular form and transport velocity

The axonal transport velocity of immunoreactive cholecystokinin (CCK) was examined in the vagal and sciatic nerves of anesthetized cats after determination of the molecular form of CCK by sequence-specific radioimmunoassay and gel chromatography. Extracts of the peripheral nerve branches, corresponding spinal ganglia, brainstem and spinal cord, contained mainly CCK-8-like immunoreactivity. In addition a large molecular form eluted immediately after the void volume of Sephadex G-50 columns, and occasionally minor C-terminal fragments were discovered. A single vagal nerve and one medulla oblongata also contained gastrin-17-like material. Significant differences in the relative amounts of the molecular forms of CCK in the different regions and nerves were not apparent. The distally directed (anterograde) flux of CCK was found to be 78 fmol/h in the sciatic nerve and 50 fmol/h in the vagus. Significant retrograde transport was not detectable. Based on these figures the true velocity for the anterograde transport was estimated to be 7 mm/h for CCK in the vagus and 8 mm/h in the sciatic nerves. The results indicate that CCK-8-like peptides are rapidly transported distally without significant axonal processing of CCK precursors.