The hypothesis that CgA-derived peptides may be involved in mechanisms modulating motility was tested. Human colonic smooth muscles were studied using an organ bath technique. Acetic acid (AA) effects were characterized on spontaneous mechanical activities (SMA) and on responses to transmural nerve stimulation (NS). AA induced a significant decrease in tone and abolished SMA; this effect was insensitive to either TTX or L-NAME/apamin. The AA-induced inhibitory effects were significantly reduced in the presence of CgA4-16. This effect was insensitive to TTX or L-NAME/apamin. Furthermore, AA-induced effects were blocked in the presence of BAYK8644 and CgA4-16 together. The inhibitory effect of nifedipine was delayed in the presence of CgA4-16. NS induced a triphasic response. Only the excitatory components were reduced in the presence of AA. This effect was dose-related and remained unchanged in the presence of CgA4-16 alone, but was blocked in the presence of simultaneous administration of CgA4-16 and L-NAME/apamin. AA application induced inhibition of human colon motility in vitro. This effect may be mediated through an action on L-type calcium channels. CgA4-16 may display a protective role, which prevents the inhibition of motility due to AA to occur, by acting on both smooth muscle and afferent terminals.
Copyright 2004 Elsevier B.V.