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infected animals showed enhanced gas accumulation in the proximal colon. Immunohistochemical detection of BDV-antioen revealed staining exclusively in the ENS and not in the muscle layers. The selective staining of neural structures was confirmed by neuron specific enolase (NSE) antibodies. In both the submucous and the myentedc plexus BDV-positive nerve fibers and cell bodies were found only in the infected animals. In the submucous plexus, BDV-positive nerve fibres and occasional BDV-positive cell bodies were found 4 weeks pJ.. The number of BDV-posifive nerve fibres and cell bodies increased dramatically between week 4 and 6 pJ. and resulted in positive staining of up to 30% of cell bodies in the submucous plexus. This proportion further increased to 50% at 14 weeks p.i. Infection of the myenteric plexus with BDV became also apparent 4 weeks p.i., but no dramatic increase with extended infection periods were observed. On average, 10% of myenteric neumnes ware BDV-positive after 4 weeks pJ.. This ratio increased up to 18% at week 14 Immunohistocheroical demonstration of choline acetyifransferase (CHAT) revealed that all BDV infected submucous neurones and 84% of the infected myenteric neurones were ChAT-positive. These data indicate that BDV colonizes the gut and dramatically affects the ENS. Like in the CNS,only subpopuiations of enteric neurones contain the BDV antigen. These neurones seemed to be primarily excitatory cholinergic neurones. Therefore it is concluded that infection of the ENS with BOV might lead to gastrointestinal dysfunctions. Furthermore, intestinal biposies may be used as

BACKGROUND: NMDA receptors (NMDA-R) are expressed on the peripheral terminals of extrinsic afferent nerves innervating the rat colon, and NMDA-R antagonists, acting peripherally, inhihit hehavioral pain responses to colorectal distension (CRD). AIM: To determine whether peripheral NMDA-R are directly involved in CRD-mediated afferent nerve activity using an isolated colon-inferior splanchnic nerve preparation. METHODS: About 4 cm of distal colon and 1 cm proximal rectum with attached inferior mesenteric artery, ganglion and inferior splanchnic nerve branches were isolated and transferred into the main chamber of an organ bath. Unit action potentials were recorded from thin nerve filaments teased from inferior splanchnic branches or the mesentery nerve. CRD was provided hy a mini-latex balloon made from a piece of fatigued latex membrane that had a diameter of ~gmm when inflated with O.4ml air. The response of units to quick inflation and withdrawal of 0.3-0.5ml of air with raising and failing phases 0.5 sec and a 2g sec plateau was tested. Distensions were repeated at intervals not less than 4 min apart. Drugs were directly administered via the inferior mesenteric artery in a volume of 0.1 ml. RESULTS: Neither vehicle, nor the non-compstitive NMDA-R open channel blocker memantine (2g/~g) administered via intra-arterial injection had any effect on ongoing basal activity. However, memantine suppressed the responses of all units to subsequent CRD more than 65%. After intra-arterial washing, the responsiveness to CRO partially recovered (-50%) indicating that the effect of memantine was reveraihle. Intra-arterial injection of 10 p.g NMDA together with 5 p.g D-serine (a required co-agonist) in low Mg 2+ Ringers (to remove voltage-dependent inhibition) transiently increased spontaneous activity more than 3-fold over basal levels. Furthermore, prior treatment with a subthreshold dose of NMDA (5 ~g) in combination with D-serine enhanced CRD mediated responses >30%. Injection of D-serine alone in low Mg 2. Ringers had no effect of basal or evoked activity. CONCLUSIONS: These results strongly suggest that NMDA-R expressed on peripheral terminals of extrinsic primary afferents of the rat colon modulate, and may be directly involved, in mechanically induced nociception in this tissue. [Supported by NIH grants DK58173 and DK48476, and funds from AstraZeneca R&D, MOIndal]