Mechanism of gastric hyperemic response during acid secretion in rats: Relation to nitric oxide, prostaglandins, and sensory neurons

The mechanism of gastric mucosal hyperemic response during pentagastrin-induced acid secretion was investigated in anaesthetized rats in relation to prostaglandins (PGs), nitric oxide (NO), and sensory neurons. A rat stomach was mounted in an es vivo chamber and perfused with saline or glycine (200 mM), and the mucosal blood now (GMBF), determined by laser Doppler flowmetry, and acid secretion was measured simultaneously, Intravenous infusion with a submaximal dose of pentagastrin (60 mu g/ kg/h) caused a significant increase in GRIEF as well as acid secretion, Such GMBF responses were totally attenuated when acid secretion was inhibited by omeprazole and cimetidine or when the luminal H+ was buffered by mucosal perfusion with glycine (200 mM). Tripelennamine, an H, antagonist, did not have any effect on acid secretory and GMBF responses to pentagastrin. On the other hand, prior administration of N-G-nitro-L-arginine methyl ester (L-NAME), the NO synthase inhibitor, significantly mitigated the increase of GMBF induced bg pentagastrin without any influence on acid secretion, and this effect was antagonized by simultaneous administration of L-arginine. The gastric hyperemic response to pentagastrin was also significantly mitigated by indomethacin or sensory deafferentation after capsaicin pretreatment with no effect on acid secretion, and was totally inhibited by combined treatments with indomethacin plus L-NAME in addition Co sensory deafferentation. Pentagastrin infusion for 8 h did not by itself cause macroscopic damage in the stomach, but additional treatments with L-NAME and indomethacin plus sensory deafferentation provoked severe lesions in the gastric mucosa, These results suggest that the gastric hyperemic response-to pentagastrin (submaximal dose) is totally dependent on H+ and that this process is mediated by endogenous NO and PGs as well as by capsaicin-sensitive sensory neurons and plays a pivotal role in maintaining mucosal integrity during acid secretion.