GASTRIC-MUCOSAL SMOOTH MUSCLES MAY EXPLAIN OSCILLATIONS IN GLANDULAR PRESSURE - ROLE OF VASOACTIVE-INTESTINAL-PEPTIDE

Background & Aims: Oscillating (3-7 cycles/min) high pressures in gast ric glands during acid secretion suggest the existence of rhythmically contracting mucosal muscles. The aim of this study was to study vasoa ctive intestinal peptide (VIP), an inhibitory neurotransmitter in the gastrointestinal tract, in relation to mucosal muscles, glandular pres sure, and blood flow. Methods: Rat, dog, and human mucosae were examin ed immunocytochemically for smooth muscle actin and VIP. Glandular pre ssure was measured using microelectrodes, red blood cell velocity (V-R BC) was measured using a cross-correlation technique, and blood flow w as measured using laser Doppler flowmetry in exposed gastric mucosa of thiobutabarbital sodium-anesthetized rats. Results: Actin immunostain ing showed muscle strands arising from muscularis mucosae, extending t oward the gastric pits. VIP-immunoreactive nerve fibers were found in close relation to these muscles. VIP, administered intra-arterially cl ose to the stomach (2 mu g/kg bolus, followed by 10 mu g . kg(-1) . h( -1)), significantly decreased glandular pressure from 18.2 +/- 1.6 to 8.9 +/- 1.6 mm Hg and almost eliminated the pressure oscillations. VIP infusion also abolished the oscillations in V-RBC and significantly i ncreased blood flow by similar to 35%. Conclusions: Contracting mucosa l muscles may be responsible for oscillations in glandular pressure an d possibly also in V-RBC. VIP probably relaxes these muscles.