Comparison of the Effects of Histamine and Nα-Methylhistamine on Neuronal Function in the Guinea-pig Oesophagus and Ileum

Abstract

The effects of histamine and N(alpha)-methylhistamine, two components of gastric juice, on vagal and transmural stimulation of the guinea-pig isolated oesophagus were compared with their effects on cholinergic and on non-adrenergic-non-cholinergic (NANC) neuronal responses in the isolated ileum, both tissues having been pretreated with mepyramine (1 microM). Histamine (< or = 10 microM) and N(alpha)-methylhistamine (< or = 1 microM) had no significant effect on either vagal or transmural stimulation in the oesophagus. Substance P, which produces a contraction by activation of cholinergic nerves in the oesophagus also was unaffected by histamine. In contrast, the agonists inhibited contractions produced by cholinergic nerve stimulation in the ileum; the inhibition produced by histamine (10 microM) was up to 73 +/- 5%, that by N(alpha)-methylhistamine (1 microM), 48 +/- 5%. Histamine also inhibited responses to stimulation of NANC neurons by up to 37 +/- 14%. The effects of histamine and N(alpha)-methylhistamine in the ileum were inhibited by clobenpropit (0.1 microM). These findings suggest that histamine and N(alpha)-methylhistamine have no role in the modulation of neuronal function in the oesophagus, in contrast with their effect in the ileum.

Lack of evidence for histamine H 3 receptor function in rat ileum and human colon

“…Subsequently, activation of the H 3 receptor has been shown to inhibit nerve transmission via cholinergic, noradrenergic and NANC neurons in the ileum, jejunum, duodenum and colon of the guinea-pig gastrointestinal tract (Trzeciakowski 1987;Coruzzi et al 1991;Leurs et al 1991;Poli et al 1991;Taylor and Kilpatrick 1992;Vollinga et al 1992;Hemedah and Mitchelson 1997;Blandizzi et al 2000), human bronchus and guinea-pig trachea (Ichinose and Barnes 1989a;Ichinose et al 1989) as well as from sensory nerves in various tissues (Ichinose and Barnes 1989b;Ohkubo et al 1995).…”