Mediators of neuronal activation in the rat brainstem following intestinal anaphylaxis

Brainstem neurones become activated following intestinal antigen challenge but the signalling mechanisms have not been resolved. Our aim was to determine the extent of brainstem activation after intestinal anaphylaxis induced by chicken egg albumin (EA). An increase in Fos-positive neurones in the nucleus tractus solitarius (nTS) was observed following EA (P<0.05). Fos-expression was decreased following pretreatment with pyrilamine and ondansetron i.p. and to a similar extent when both antagonists were administered together (all P<0.05 vs. control). Indomethacin had no effect on Fos-expression after antigen challenge. 5-HT and histamine but not prostanoids, released following intestinal anaphylaxis, induce nTS activation via histamine H(1)- and 5-HT(3) receptors. Information on the intestinal inflammatory status is relayed centrally and may play a role in reflexes and behavioural responses to activation of the immune system.