ALTERED NEUROPEPTIDE CONTENT AND CHOLINERGIC ENZYMATIC-ACTIVITY IN THE INFLAMED GUINEA-PIG JEJUNUM DURING PARASITISM

We investigated the effects of an enteric infection with the parasitic nematode, Trichinella spiralis, on peptidergic and cholinergic neural pathways of the guinea pig jejunum. The content of the enteric neurop eptides, substance P (SP) and vasoactive intestinal peptide (VIP), and the activities of the key cholinergic enzymes, acetylcholinesterase ( AChE) and choline acetyltransferase (ChAT), were measured and compared in extracts of jejunal muscularis externa (ME) obtained from uninfect ed jejunum and T. spiralis-inflamed jejunum. Significant decreases wer e detected in both SP immunoreactivity and AChE activity on days 6 and 10 postinfection (PI) in nematode-infected guinea pig jejunum compare d to uninfected controls. The maximum changes observed for SP and AChE both occurred on day 10 PI and were evident as decreases of 37% and 4 8%, respectively, from the mean uninfected control values for SP and A ChE. In contrast, VIP immunoreactivity and ChAT activity showed no sig nificant changes during the enteric phase of T. spiralis infection. Ne matode-evoked histopathological changes in jejunal tissues from infect ed animals were associated with significant increases in myeloperoxida se (MPO) activity, an index of inflammation intensity, which occurred on day 6 PI (885% of mean control) and day 10 PI (469% of mean control ) coinciding temporally with the significant decrease in SP content an d AChE activity during infection. Thus, intestinal motor disturbances observed in mammalian hosts during enteric nematode infections involve inflammation-generated changes in the neurohumoral control of smooth muscle function.