By using a strategy based on nucleotide sequence homology, we have cloned an intronless DNA encoding a new putative member of G protein-coupled receptors. The deduced amino acid sequence of the rat OL1 receptor, together with its expression at high levels in a small subset of cells in the olfactory neuroepithelium indicate that OL1 is related to the recently discovered olfactory multigene family. PCR and in situ hybridization analyses showed the OL1 transcripts to be not only expressed in the olfactory epithelium, but also in the heart. This unexpected cardiac expression was developmentally regulated, being maximal at early postnatal stages and hardly detectable at adult stages. Moreover, this observation was not restricted to OL1 since it was extended to other putative olfactory receptors. Although its functional significance remains unknown, this transient cardiac expression suggests that receptors belonging to the olfactory superfamily, could be not only involved in odor coding, but also in cardiac morphogenesis. Another olfactory-specific gene transcript encoding PTP NE-3, a recently cloned receptor-type protein-tyrosine phosphatase, could also be detected in heart. The very low levels of expression observed in rat embryo and at early postnatal stages as compared to adult stages, suggest that protein-tyrosine phosphatases, as well as protein-tyrosine kinases, may play a role in the control of cardiac cell growth and morphogenetic processes.