PROSTAGLANDIN E-2 ACTIVATION OF VIP SECRETOMOTOR NEURONS IN THE GUINEA-PIG ILEUM

The effect of prostaglandin E-2 (PGE(2)) on the activity-related expre ssion of the proto-oncogene c-fos in specific populations of enteric n eurons was investigated. Segments of guinea-pig ileum were incubated i n vitro in the presence or absence of PGE(2), and whole mounts of the myenteric and submucosal plexus were prepared for immunocytochemical l ocalization of Fos, VIP and NPY. Control tissues exhibited a low numbe r of Fos-immunoreactive (Fos-IR) neurons (7 +/- 2% of total). Incubati on of the tissues with 10-1000 nM PGE(2) for 30 min caused a concentra tion-dependent increase in Fos-IR submucosal neurons (maximum at 100 n M; 39 +/- 6%), which was not inhibited by TTX. PGE(2) did not evoke an increase in Fos-IR myenteric neurons. In double labeling experiments, Fos colocalized exclusively with VIP in the submucosal plexus, and no t with NPY. Exposure of stripped segments of guinea pig ileum in Ussin g chambers to 100 nM PGE(2) evoked an increase in short circuit. curre nt (20 +/- 7 mu A/cm(2)), of which the initial rapid phase could be ab olished by TTX, and not by atropine and hexamethonium. It is concluded that PGE(2) can activate VIP non-cholinergic secretomotor neurons. (C ) 1997 Elsevier Science B.V.