Control of the human ileocaecal junction: an in vitro analysis of adrenergic and non-adrenergic non-cholinergic mechanisms.

Circular muscle strips from the human ileocaecal junction developed myogenic tone (sustained resting tension) in vitro and showed an obvious component of relaxation in response to electrical field stimulation. These features are considered typical of sphincteric muscle because circular muscle strips from terminal ileum 1-2 cm proximal to the junction and from the caecum or ascending colon 1-2 cm distal to the junction developed little or no tone and showed predominantly contractile responses to electrical-field stimulation. In 18 out of 29 specimens, junctional strips showed excitatory responses to adrenaline or noradrenaline. The relaxation of junctional strips was non-adrenergic non-cholinergic (NANC) in nature. Nitric oxide appears to be involved in the NANC relaxation.