Incorporation of imipramine into isolated rat peritoneal mast cells in vitro

Impaired parasympathetic function increases susceptibility to inflammatory bowel disease in a mouse model of depression

Clinical and experimental evidence indicates that intestinal inflammatory conditions can be exacerbated by behavioral conditions such as depression. The recent demonstration of a tonic counterinflammatory influence mediated by the vagus nerve in experimental colitis provides a potential link between behavior and gut inflammation. Here we show that experimental conditions that induced depressive-like behaviors in mice increased susceptibility to intestinal inflammation by interfering with the tonic vagal inhibition of proinflammatory macrophages and that tricyclic antidepressants restored vagal function and reduced intestinal inflammation. These results show that reserpine-induced monoamine depletion and maternal separation, 2 models for depression, produced a vulnerability to colitis by a mechanism involving parasympathetic transmission and the presence of gut macrophages. The tricyclic antidepressant desmethylimipramine protected against this vulnerability by a vagal-dependent mechanism. Together these results illustrate the critical role of the vagus in both the vulnerability to inflammation induced by depressive-like conditions and the protection afforded by tricyclic antidepressants and rationalize a clinical evaluation of both parasympathomimetics and tricyclic antidepressants in treatment of inflammatory bowel disease.

Inhibition of reserpine, guanethidine and imiparmine of the uptake of 5-hydroxytryptamine by rat peritoneal mast cells in vitro

The effect of reserpine, guanethidine and imipramine of the uptake of tritiated 5-hydroxytryptamine by rat peritoneal mast cells was studied in vitro. The Km value for uptake of 5-hydroxytryptamine was 3 x 10(-7) M in this study. Kinetic analysis of the data obtained suggests that the drugs inhibits the uptake in a competitive manner, in the order of decreasing potency: reserpine, imipramine, guanethidine. For reserpine the Dixon plot resulted in two curves, each composed of 2 linear components suggesting inhibition of uptake of 5-hydroxytryptamine at 2 different levels or by 2 different mechanisms with different K1 values. It is suggested that the higher K1 value, representing an immediate effect of reserpine, stands for inhibition of uptake at the cell membrane. The lower K1 value possibly represents inhibition at the level of the membrane surrounding the intracellular storage organelles.