Salvinorin A inhibits colonic transit and neurogenic ion transport in mice by activating κ-opioid and cannabinoid receptors

Abstract  The major active ingredient of the plant Salvia divinorum , salvinorin A (SA) has been used to treat gastrointestinal (GI) symptoms. As the action of SA on the regulation of colonic function is unknown, our aim was to examine the effects of SA on mouse colonic motility and secretion in vitro and in vivo . The effects of SA on GI motility were studied using isolated preparations of colon, which were compared with preparations from stomach and ileum. Colonic epithelial ion transport was evaluated using Ussing chambers. Additionally, we studied GI motility in vivo by measuring colonic propulsion, gastric emptying, and upper GI transit. Salvinorin A inhibited contractions of the mouse colon, stomach, and ileum in vitro , prolonged colonic propulsion and slowed upper GI transit in vivo . Salvinorin A had no effect on gastric emptying in vivo . Salvinorin A reduced veratridine-, but not forskolin-induced epithelial ion transport. The effects of SA on colonic motility in vitro were mediated by κ-opioid receptors (KORs) and cannabinoid (CB) receptors, as they were inhibited by the antagonists nor-binaltorphimine (KOR), AM 251 (CB₁ receptor) and AM 630 (CB₂ receptor). However, in the colon in vivo , the effects were largely mediated by KORs. The effects of SA on veratridine-mediated epithelial ion transport were inhibited by nor-binaltorphimine and AM 630. Salvinorin A slows colonic motility in vitro and in vivo and influences neurogenic ion transport. Due to its specific regional action, SA or its derivatives may be useful drugs in the treatment of lower GI disorders associated with increased GI transit and diarrhoea.