Vanilloid receptor type 1-immunoreactivity is expressed by intrinsic afferent neurones in the guinea-pig myenteric plexus.

The enteric sensory nervous system consists of extrinsic and intrinsic components. The cellular distribution of vanilloid receptor type 1 (VR1) and its relation to the intrinsic sensory neurones were studied in myenteric plexus-longitudinal muscle preparations of rat ileum and guinea-pig ileum and colon. VR1-immunoreactivity was localized on fine fibres and expressed by ganglionic cells. In the guinea-pig myenteric plexus, a proportion of VR1-immunoreactive cells co-localized with calbindin, a marker for intrinsic afferent neurones. Reverse transcription-polymerase chain reaction with rat VR1-specific primers detected VR1 mRNA in rat but not in guinea-pig preparations. We conclude that VR1 is expressed on fibres and by myenteric neurones. In the guinea-pig, VR1 is expressed by intrinsic afferent neurones but its mRNA may differ from the rat sequence in the region of the primers.