Somatostatin as a neurotrophic factor - Which receptor/second messenger transduction system is involved?

variety of studies support a trophic role for somatostatin in the developin g nervous system, evidenced as stimulation of neurite outgrowth and axonal or neuronal migration in both in vivo and culture models. Cloning experimen ts have now demonstrated the existence of five subtypes of somatostatin rec eptor, differentially distributed in the nervous system, differentially lin ked to specific signal transduction systems and in certain cases differenti ally expressed during development. The combination of the differential and developmental regulation of expression of both the somatostatin peptides an d their receptors thus provides great potential in terms of trophic effects . To sustantiate trophic effects of somatostatin, data are presented from t wo different model systems, cultures of cerebellar granule cells as well as transgenic mice in which somatostatin is expressed under the control of th e glial fibrillary acidic protein promoter. Finally, potential receptor sub types and second messenger systems involved in these trophic effects are ad dressed.