[Effects of cyclic adenosine-3',5'-monophosphate and cyclo(Lys-Pro).HCl neuronotrophic factors in tissue culture]

Explants and cell cultures of embryonic chick ganglia trigeminalia, telencephalon and retina or hippocampus from fetal rats were incubated in maximow chambers in the presence of cyclic AMP and the dipeptide cyclo(Lys-Pro).HCL under various conditions. Maintenance of nerve cells and growth of nerve fibers were observed by morphometrical methods. 1. Cyclo(Lys-Pro).HCL promoted the maintenance of neuroblasts and the growth of nerve fibres in explants of the ganglion trigeminal and retinal cell cultures. The effect depended on the presence of serum in the medium by use of poly-I-lysine substrate. 2. Extern applicated cyclic AMP and the dipeptide SP3-4 = cyclo(Lys-Pro).HCL facilitated neurite growth in PNS cultures. In the presence of the drugs the length of nerve fibers increased for a short term. On CNS explants substance P (SP1-11) and SP3-4 were without effect. Cyclic AMP stimulated the growth of nerve fibers in CNS explants and cell cultures in number and length. 3. Discussed is the effect of SP1-11 and cyclo(Lys-Pro).HCL for competence of nerve fibre regeneration in vitro in relation to increasing cAMP levels, which may then act as an initial second messenger. It is suggested that explants and cell cultures of nervous tissues will be useful as a tool for the further characterisation of factors with neuronotrophic activities.