EFFECT OF TRUNCAL VAGOTOMY AND CAPSAICIN ON MAST-CELLS AND IGA-POSITIVE PLASMA-CELLS IN RAT JEJUNAL MUCOSA

Immunocompetent cells, including mast cells and plasma cells (PC), in the intestinal mucosa are closely apposed to nerve fibres. Recent work has shown that vagal afferent nerves penetrate the jejunal mucosa and contact intestinal mucosal mast cells (IMMC); and that electrical sti mulation of the vagus results in increased IMMC histamine content. To determine if the vagus nerve exerts a trophic effect on immunocompeten t cells in the gut mucosa, the effects of truncal vagotomy and neonata l capsaicin treatment on IMMC and IgA containing PC in the lamina prop ria of rat jejunum were investigated. Three weeks after vagotomy, micr odensitometric assessment of Alcian blue stained sections revealed 25% fewer IMMC in vagotomized animals than in controls (P<0.05). Three mo nths after neonatal capsaicin administration 28% fewer IMMC were found in treated rat jejunum, compared with littermate controls (P<0.05). T hree weeks post-surgery, IgA-PC densities were increased in both vagot omized animals (that also underwent pyloroplasty) and pyloroplasty con trols, compared to animals subjected to laparotomy only. The proportio n of lamina propria areas remained stable, indicating that the observa tions reflected real reductions in the numbers of IMMC. We also determ ined the densities of B-50 (a nerve growth-associated protein, also ca lled GAP-43) immunoreactive nerve fibres in the lamina propria, as wel l as nerve profile areas, three weeks after vagotomy, and these parame ters were unchanged. Taken together, these findings support the hypoth esis that the vagus exerts a trophic effect on IMMC; and that capsaici n-sensitive nerves also affect the IMMC population. These data add to the growing body of evidence for a functional connection between IMMC and the nervous system.