Local release of monoamines in the gastrointestinal tract: an in vivo study in rabbits.

Dialysis fibers chronically implanted into the gastric submucosa of rabbits allowed us to collect an interstitial fluid (I.S.F.) dialysate in which biogenic amine concentrations were measured, and compared with those obtained from plasma and tissue samples. The results suggest that I.S.F. concentrations represent a good assessment of the local release of the amines by enteric nerves and/or paracrine cells, under basal conditions. The fact that acetylcholine and neostigmine, when perfused through the dialysis system, increased I.S.F. serotonin (5-HT) concentrations, supports a cholinergic modulation of the release of 5-HT within the gastrointestinal wall, and validates the dialysis method as a powerful tool to monitor, in vivo, dynamic changes in I.S.F. monoamine concentrations.