Vago‐vagal activation of naloxone‐sensitive non‐adrenergic, non‐cholinergic jejunal contractions in the anaesthetized cat

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Abstract
Experiments were performed on chloralose‐anaesthetized cats, pretreated with guanethidine and with ligated adrenals and sectioned splanchnic nerves. The animals were paralysed and artificially ventilated. Jejunal motility was recorded by an intraluminal balloon, as volume changes at a constant pressure. Cervical or abdominal vagal afferent stimulation was performed before and after the administration of atropine. In both circumstances jejunal contractions were elicited. The latency of onset and the duration of the responses were significantly shorter before than after atropine. Strength‐duration and frequency‐response relationships, respectively, did not differ significantly prior and subsequent to atropine. Naloxone (0.05–0.5 mg kg‐1i.v.) blocked these reflexly induced atropine‐resistant jejunal contractions, as did section of the contralateral vagus. Possible mechanisms of action of these putative opioid receptor‐mediated neurogenic effects are discussed. The present study demonstrates that nonadrenergic, non‐cholinergic, naloxone‐sensitive jejunal contractions can be elicited as a vago‐vagal reflex, where the receptive field seems to be located within the abdominal cavity.