Vol. 305, Issue 2, 733-739, May 2003

Kinin-Induced Anion-Dependent Secretion in Porcine Ileum: Characterization and Involvement of Opioid- and Cannabinoid-Sensitive Enteric Neural Circuits

Benedict T. Green¹ , Andrew Calvin, Scott M. O'Grady and David R. Brown

Departments of Veterinary PathoBiology, College of Veterinary Medicine, (B.T.G., A.C., D.R.B.) and Animal Science-Physiology, College of Agriculture, Food, and Environmental Sciences (S.M.O.), University of Minnesota, St. Paul, Minnesota

The intestinal secretory actions of the proinflammatory peptide kallidin (lysyl-bradykinin) are mediated partially by enteric neurons. We hypothesized that kallidin produces neurogenic anion secretion through opioid- and cannabinoid-sensitive enteric neural pathways. Changes in short-circuit current (I_sc) across sheets of porcine ileal mucosa-submucosa mounted in Ussing chambers were measured in response to kallidin (1 µM) or drugs added to the contraluminal bathing medium. Kallidin transiently increased I_sc, an effect reduced after inhibition of neuronal conduction by 0.1 µM saxitoxin, cyclooxygenase inhibition by 10 µM indomethacin, or kinin B₂ receptor blockade by 1 µM D-arginyl-L-arginyl-L-prolyl-trans-4-hydroxy-L-prolylglycyl-3-(2-thienyl)-L-alanyl-L-seryl-D-1,2,3,4-tetrahydro-3-isoquinolinecarbonyl-L-(2,3,7)-octahydro-1H-indole-2-carbonyl-L-arginine (HOE-140). Its action was dependent upon extracellular Cl or HCO ions, but was resistant to 10 µM bumetanide or 0.3 mM 4,4'-diisothiocyanatostilbene-2,2'-disulfonic acid, and seemed to involve luminal alkalinization as measured by pH-stat titration. Kallidin-induced I_sc elevations were sensitive to saxitoxin in tissues bathed in Cl-, but not HCO-deficient media. Tissues pretreated with 0.1 µM [D-Pen^2,5]-enkephalin, a selective -opioid agonist, displayed reduced I_sc responses to kallidin; this effect was prevented by the -opioid antagonist naltrindole. At a contraluminal concentration of 1 µM, the cannabinoid receptor agonist (6aR)-trans-3-(1,1-dimethylheptyl)-6a,7,10,10a-tetrahydro-1-hydroxy-6,6-dimethyl-6H-dibenzo[b,d]pyran-9-methanol (HU-210) also attenuated responses to kallidin. Proinflammatory kinins seem to stimulate neurogenic anion secretion in porcine ileum by activating enteric neural circuits expressing inhibitory opioid and possibly cannabinoid receptors.