High ciliary neuronotrophic specific activity in rat peripheral nerve.

Ciliary neuronotrophic factors (CNTFs) are proteins defined by their ability to promote the survival in tissue culture of chick embryo ciliary ganglionic neurons. CNTF activity has been reported in several source materials. Among these sources, the highest specific activity, i.e. 16,000 TU/mg, has been found in the intraocular tissue innervated by the ciliary ganglionic neurons. We now report that extracts of adult rat peripheral nerve and spinal nerve roots contain CNTF at a specific activity equal to or greater than the intraocular tissue. Equally high concentrations of CNTF activity are found in both motor and sensory nerves. The possible cellular source(s) of this mammalian CNTF is discussed.