Afferent innervation of the gallbladder in the cat, studied by the horseradish peroxidase method

Following injection of horseradish peroxidase (HRP) into the wall of the gallbladder of cats, HRP-positive cells were found bilaterally in dorsal root ganglia T2-L3 (T2-L2, and T3-L2/L3 also observed in a few cats) and nodose ganglia. In about 33% of animals labelled cells were also distributed in cervical dorsal root ganglia C5-C7. Labelled cells were more frequently localized on the right side than the left. There was no apparent change in numbers of labelled cells in the nodose ganglion (NG) on either side following greater and lesser splanchnicotomy or section of the right phrenic nerve or removal of the celiac ganglion. After severing both the greater and lesser splanchnic nerves unilaterally, numbers of labelled afferent cells from the gallbladder in dorsal root ganglia (DRGs) significantly decreased on the ipsilateral side but there was no change in the pattern of distribution contralaterally. After section of the right phrenic nerve, labelled cells were not found in ipsilateral cervical ganglia. That some afferent fibers from the gallbladder travel via the phrenic nerves, particularly on the right side, may be a supplementary mechanism in the generation of referred pain in gallbladder disease. The splanchnic nerves are the main, but not the only pathway for afferent fibers from the gallbladder.