Neuronal synthesized insulin roles on neural differentiation within fetal rat neuron cell cultures

We previously, described the production and secretion of insulin by fetal n eurons in culture and demonstrated that neuronal synthesized insulin [I(n)] promoted neurofilament distribution and axonal growth. In this study we in vestigated the role of T(n) in promoting neural differentiation. Stem cells from 16 day gestational age rat brains were cultured in an insulin-free de fined medium (IFDM) and treated with: 5, 20 or 100 ng/ml of exogenous insul in, 100 ng/ml insulin-like growth factor I (IGF-I) or an anti-insulin antib ody. The neurons were studied at 1 and 3 days of incubation. The total numb er of cells showed no significant difference (P>0.05) in any of the media u sed, except the IFDM at day 3 of incubation treated with the anti-insulin a ntibody (P<0.05) and IGF-I to 20 ng/ml of insulin (P<0.05). No significant difference (P>0.05) was found in the number of differentiated neurons incub ated in the IFMD, in which the neurons produce and secrete I(n), between da ys 1 and 3 of incubation, but neural differentiation decreased significantl y (P<0.05) when treated with the anti-insulin antibody. Exogenous insulin s ignificantly increased (P<0.05) the number of differentiated neurons compar ed to the IFDM. A significant reduction (P<0.05) of differentiated neurons was observed at day 3 of incubation with IGF-I compared to all the differen t media. Thus, T(n) has a role in promoting neural differentiation and grow th, but exogenous insulin promoted neural differentiation and growth beyond I(n). <(c)> 2001 Elsevier Science B.V. Ail rights reserved.