The expression patterns of serine/threonine kinase receptors in the central nervous system of the developing and adult rat were studied by in situ hybridization. The recently cloned bone morphogenetic factor receptor type II (BMPR-II) was compared with the ActR-II and several type I receptors including ActR-I, ActR-IB, BMPR-IA, BMPR-IB and TbetaR-I. We found that these receptors are spatially and temporally regulated. As early as embryonic day 11 (E11), BMPR-II mRNA was expressed in the neuroepithelium in brain and spinal cord. At E15, the expression of ActR-II mRNA was stronger than that of BMPR-II in the spinal cord, followed in intensity by the expression of ActR-I, ActR-IB, BMPR-IA, BMPR-IB and TbetaR-I mRNA. The BMP type I receptors were expressed only in the ependymal epithelium and in the sympathetic ganglia at E15. Many of the examined receptor mRNAs were expressed at peak levels in the brain around birth. In the adult brain, mRNA for BMPR-II was expressed in different patterns together with ActR-II and ActR-I. Thus, BMPR-II mRNA was found in neurons of the cortex, dentate gyrus, hippocampus, habenula and substantia nigra. ActR-II, ActR-I, ActR-IB and, weakly, TbetaR-I were all expressed in the dentate gyrus. In contrast mRNA for BMPR-IA and BMPR-IB was not found in the adult brain. It is suggested that the expressed receptors may mediate actions of members of the TGFbeta superfamily, e.g. BMPs, controlling the development and plasticity in the nervous system.