G protein-coupled receptor for histamine, primarily mediating gastric acid secretion. Predominantly expressed in the gastric mucosa, couples to G(s) G alpha proteins upon histamine binding, leading to activation of adenylate cyclase and increased intracellular cyclic AMP (cAMP) levels (PubMed:38647423, PubMed:39333117). This signaling cascade stimulates parietal cells to secrete hydrochloric acid, playing a key role in digestive physiology. Also expressed in other tissues, including the heart and central nervous system, where it may contribute to cardiac stimulation and modulate neurotransmitter release (By similarity). {ECO:0000250|UniProtKB:P97292, ECO:0000269|PubMed:38647423, ECO:0000269|PubMed:39333117}. This is the function of HRH2 (histamine receptor H2, Ensembl gene identifier ENSG00000113749).