Role of sensory afferents in the myoelectric response to acute enteric inflammation in the rabbit.

The role of sensory afferents in inflammation-induced alterations in myoelectric activity in vivo was investigated in the rabbit small intestine. Isolated ileal loops were implanted with serosal electrodes and exposed to ricin or vehicle after pretreatment with 125 mg/kg of subcutaneous (125 mg over 3 days) or intraluminal (640 microM) capsaicin. After 5 h of myoelectric recording, the loops were prepared for histology and for ex vivo generation of eicosanoids. Capsaicin exacerbated mucosal damage after exposure to ricin but did not alter neutrophil infiltration. Subcutaneous capsaicin alone elevated slow-wave frequency and spike events and transiently suppressed the myoelectric response to ricin. In contrast, intraluminal capsaicin alone did not alter myoelectric activity but produced a sustained inhibition of the response to ricin. Eicosanoid production was unchanged by capsaicin alone. Intraluminal capsaicin blocked increases in leukotriene C4 and prostaglandin E2 during inflammation, an effect that paralleled its inhibition of myoelectric activity. Thus the contribution of sensory afferents to altered motility during acute ileitis involves the release of mucosal inflammatory mediators that influence neural control of smooth muscle.