Histaminergic involvement in thyrotropin-releasing hormone stimulation of antral tissue in the rat.

The mechanism of action of thyrotropin-releasing hormone on antral motility was investigated in vitro. With the recent detection of thyrotropin-releasing hormone in gastrointestinal tissue, the possibility exists that the peptide may play a physiologic role in gastrointestinal motility. Results indicate that the hormone stimulates antral motility through a non-cholinergic excitatory pathway based on the inability of the muscarinic antagonist, atropine, to block the response. A histaminergic pathway is an attractive possibility to explain the excitatory response, because both pyrilamine and cimetidine inhibit the thyrotropin-releasing hormone induced response and the peptide has no further influence on antral motility after the tissue is exposed to a supramaximal concentration of histamine.