Cholinergic-adrenergic interactions on intestinal ion transport.
The autonomic control of intestinal electrolyte transport has been investigated in the in vitro, short-circuited rabbit ileum with varying doses of carbachol and with neuroeffector blocking agents. Low-dose carbachol (less than 10(-6) M) and high-dose carbachol (greater than 10(-4) M) had different effects on Na and Cl transport. Low-dose carbachol caused a transient increase in the potential difference and short-circult current, stimulated Cl secretion, and inhibited the residual flux (probably HCO3 secretion). This is a muscarinic response since it is inhibited by atropine (10(-6) M). After an initial increase of the potential difference and short-circuit current, high-dose carbachol reduced these electrical parameters, stimulated Na and Cl absorption, and abolished the residual flux. This is a nicotinic response since it is inhibited by hexamethonium (10(-5) M). This nicotinic response is identical to that reported by others with alpha-adrenergic agents and it was inhibited also by phentolamine (10(-7) M). We propose that high-dose carbachol stimulates nicotinic receptors on postganglionic sympathetic fibers present in our preparations causing a release of catecholamines and a resulting alpha-adrenergic response by the intestinal epithelial cell. The physiological significance of this response in the gut remains to be determined.
D000818:Animals; D001285:Atropine / Q000494:pharmacology; D002217:Carbachol / Q000494:pharmacology; D002712:Chlorides / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D006584:Hexamethonium Compounds / Q000494:pharmacology; D066298:In Vitro Techniques; D007408:Intestinal Absorption / Q000187:drug effects; D007421:Intestine, Small / Q000378:metabolism*; D010275:Parasympathetic Nervous System / Q000502:physiology*; D010643:Phenoxybenzamine / Q000494:pharmacology; D011817:Rabbits; D011942:Receptors, Adrenergic, alpha / Q000502:physiology; D011976:Receptors, Muscarinic / Q000502:physiology; D011978:Receptors, Nicotinic / Q000502:physiology; D012964:Sodium / Q000378:metabolism*; D013564:Sympathetic Nervous System / Q000502:physiology*
D002712:Chlorides; D006584:Hexamethonium Compounds; D011942:Receptors, Adrenergic, alpha; D011976:Receptors, Muscarinic; D011978:Receptors, Nicotinic; D010643:Phenoxybenzamine; D001285:Atropine; D002217:Carbachol; D012964:Sodium