The serotonin (5-HT)(1A) receptor agonists have already been shown to protect cultured neurons from excitotoxic as well as from apoptotic damage [B. Ahlemeyer, J. Krieglstein, Stimulation of 5-HT1A receptors inhibits apoptosis induced by serum deprivation in cultured neurons from chick embryo, Brain Res. 777 (1997) 179-186.; B. Ahlemeyer, A. Glaser, C. Schaper, I. Semkova, J. Krieglstein, The 5-HT1A receptor agonist, Bay x 3702, inhibited apoptosis induced by serum deprivation in cultured neurons, Fur. J. Pharmacol. 370 (1999) 211-216., J.H.M. Prehn, M. Welsch, C. Backhauss, J. Nuglisch, F. Ausmeier, C. Karkoutly, J. Krieglstein, Effects of serotonergic drugs in experimental brain ischemia: evidence for a protective role of serotonin in cerebral ischemia, Brain Res. 630 (1993) 110-120.; I. Semkova, P. Wolz, J. Krieglstein, Neuroprotective effect of 5-HT1A receptor agonist, Bay x 3702, demonstrated in vitro and in vivo, fur. J. Pharmacol. 359 (1998) 251-260., B. Suchanek, H. Struppeck, T. Fahrig, The 5-HT1A receptor agonist, Bay x 3702, prevents staurosporine-induced apoptosis, Bur. J. Pharmacol. 355 (1998) 95-101.] and to increase the release of the neurotrophic protein, S-100 beta [P.M. Whitaker-Azmitia, R. Murphy, E.C. Azmitia, Stimulation of astroglial 5-HT1A receptors releases the serotonergic growth factor, protein S-100, and alters astroglial morphology, Brain Res. 497 (1989) 80-86.3 P.M. Whitaker-Azmitia, R. Murphy, E.C. Azmitia, S-100 protein is released from astroglial cells by stimulation of 5-HT1A receptors, Brain Res. 528 (1990) 155-158.]. In this study, we tried to find out whether S-100 beta can protect cultured neurons from glutamate- and staurosporine-induced damage and whether the neuroprotective activity of the highly selective 5-HT1A receptor agonist, Bay x 3702, is mediated by an induction of S-100 beta. Extracellularly added S-100 beta (1-10 ng/ml) reduced staurosporine-induced damage in pure neuronal cultures from chick embryo telencephalon as well as in mixed neuronal/glial cultures from neonatal rat hippocampus. In addition, S-100 beta (1 ng/ml) reduced neuronal death induced by exposure to glutamate (0.25 mM, 30 min) in mixed neuronal/glial cultures from neonatal rat hippocampus. In cultured rat cortical astrocytes, a 24 h-treatment with Bay x 3702 (1 nM) increased the S-100 beta content in the culture medium from 2.2 +/- 0.3 (controls) to 6.2 +/- 0.7 ng/ml. In the adult rat, a 4 h-infusion of 4 mu g/kg Bay x 3702 (i.v.) was found to increase the S-100 beta content in the striatum 6 h after the beginning of the infusion to 153 +/- 37 mu g/g compared with 60 +/- 20 mu g/g in vehicle-treated rats. Bay x 3702 had no effect on the S-100 beta content in the rat hippocampus. Finally, we tried to block the protective effect of Bay x 3702 against staurosporine-induced damage in mixed neuronal/glial cultures from rat neonatal hippocampus by anti-S-100 beta antibodies. We found only a partial blockade, although the antibodies fully blocked the antiapoptotic effect of S-100 beta itself demonstrating that the antibody was effective in blocking neuroprotection by S-100 beta. Thus, we conclude that S-100 beta was able to protect cultured neurons against glutamate- and staurosporine-induced damage. Furthermore, S-100 beta mediated partially the protective effect of the 5-HT1A receptor agonist, Bay x 3702 against staurosporine-induced apoptosis in mixed neuronal/glial cultures from neonatal rat hippocampus. (C) 2000 Elsevier Science B.V. All rights reserved.
