A rat histamine H1 receptor gene which lacked introns was isolated from a rat genomic library using recently cloned bovine histamine H1 receptor cDNA [Yamashita et al., Proc. Natl. Acad. Sci. USA, 88, 11515-11519 (1991)]. The receptor protein deduced from this isolated gene was composed of 486 amino acids and showed characteristic properties of G protein-coupled receptors. At the 5'-flanking region of the receptor gene, we have located potential TATA box sequences and consensus sequences for the glucocorticoid response element and AP-2 element. After being subcloned into a mammalian expression vector, the isolated gene was transfected to C6 glioma cells. These cells showed significant binding toward [3H]mepyramine. The binding was inhibited by H1 antagonists or histamine. The mode of this binding was comparable to the binding of membranes derived from rat tissues toward [3H]mepyramine. Northern blot analysis detected a 3.0 kb nucleotide band for histamine H1 receptor mRNAs from rat brain and small intestine when these mRNAs were hybridized with the isolated rat H1 gene. The present results demonstrate the isolation of the rat histamine H1 receptor gene.