A ciliary neuronotrophic factor from peripheral nerve and smooth muscle which is not retrogradely transported

We have found that a CNTF-like molecule which supports ciliary and sympathetic neurons is not retrogradely transported in either sympathetic or parasympathetic nerves. The factor has an apparent M_r of 21 kDa, a pI of 4.9, and is present in peripheral nerves and smooth muscle of the chick. Our experiments indicate that CNTF-like activity does not accumulate on the distal side of ligated chick expansor nerves. In contrast, there is a clear accumulation of NGF. The activity further differs from NGF in that it is not removed from a smooth muscle of the chick wing by innervating sympathetic fibers. Transection of these fibers does not lead to an accumulation of ciliary activity in the expansor secundariorum muscle, suggesting that neurons do not actively deplete the muscle of factor by retrograde transport. Finally, recombinant CNTF or semi-purified preparations of CNTF-like activity labelled with¹²⁵I were not transported to the ciliary ganglion of chicks following injection of biologically active material into the eye. Our results suggest either that endogenous CNTF does not act as a survival factor in vivo, or that retrograde transport is not a property inherent to all neuronotrophic molecules.