The Journal of Neuroscience, October 1, 1998, 18(19):8065-8073
Duodenal Sensory Neurons Project to Sphincter of Oddi Ganglia
in Guinea Pig
Audra L.
Kennedy and
Gary M.
Mawe
Department of Anatomy and Neurobiology, The University of Vermont,
Burlington, Vermont, 05405
Retrograde labeling of duodenum-sphincter of Oddi (SO)
preparations in vitro with the carbocyanine dye DiI
revealed that duodenal neurons project to the SO. The
duodenum-SO-projecting neurons were immunoreactive (IR) for choline
acetyltransferase but not nitric oxide synthase or calretinin,
indicating that this is a cholinergic projection and that this pathway
is distinct from the circuitry involved in the ascending limb of the
peristaltic reflex. Approximately 20% of the duodenum-SO projection
neurons were IR for calbindin. Calbindin-IR nerves within SO ganglia
degenerated when the SO was maintained in organ culture alone, but
persisted when the SO was cultured with the duodenum intact. Therefore, SO ganglia are a target of the calbindin-positive duodenum-SO projection. Because calbindin is a marker of intrinsic sensory neurons
that have processes that pass to the mucosa, these neurons are in
position to detect the release of a compound from the mucosa and signal
its release to SO ganglia. When applied to retrogradely labeled
neurons, cholecystokinin (CCK) elicited a prolonged depolarization, indicating that duodenum-SO-projecting neurons could be capable of
detecting CCK released from the mucosa. It is proposed that the role of
the intrinsic sensory neurons that project to the SO may be to signal
the postprandial release of CCK, thus providing an instruction to
decrease SO resistance and facilitate the flow of bile into the
duodenum.
Key words:
enteric nervous system; myenteric plexus; calbindin; sphincter of Oddi; duodenum; sensory neurons; cholecystokinin
Copyright © 1998 Society for Neuroscience 0270-6474/98/18198065-09$05.00/0