Background  Cellular prion protein (PrP^C) is expressed in the enteric nervous system (ENS), however, its physiological role has not been identified. Studies suggest that PrP^C can function as a metal‐binding protein, as absence of the protein has been linked to altered copper metabolism and atypical synaptic activity. Because copper is known to modulate smooth muscle relaxation, we tested the hypothesis that PrP^C deficiency would alter intestinal contractility.

Methods  We examined electrically evoked ileal contractility in Prnp^−/− or wild type littermate mice and the effects of copper or copper chelation. PrP^C expression was studied in whole mount ileal preparations of mice and guinea pigs by immunohistochemistry.

Key Results  Relative to wild type mice, ileal tissues of Prnp^−/− mice exhibited reduced electrical field stimulation (EFS)‐evoked contractility. Furthermore, EFS‐induced relaxation, as a percentage of that induced by a nitric oxide donor, was enhanced. Addition of a copper donor to the organ bath increased, whereas the addition of a copper chelator inhibited, nitric oxide donor‐induced ileal relaxation in Prnp^−/− mice. PrP^C was expressed on nerve fibers or terminals, and some cell bodies in the myenteric and submucosal plexuses of wild type mice. PrP^C colocalized with a neuron‐specific ectonucleotidase, nucleoside triphosphate diphosphohydrolase 3 (NTPDase3), but to only a limited extent with GFAP, a marker of enteric glia. Guinea pigs expressed PrP^C in nerve fibers or terminals and enteric glia in the myenteric and submucosal plexuses.

Conclusions & Inferences  Our findings suggest that PrP^C, which is abundant in the ENS, has a role in the regulation of ileal contractility.