Expression and regulation of cholecystokinin and cholecystokinin receptors in rat nodose and dorsal root ganglia

Abstract

Cholecystokinin (CCK) is an important satiety factor, acting via the vagus nerve to influence central feeding centers. CCK binding sites have been demonstrated in the vagal sensory nodose ganglion and within the nerve proper. Using in situ hybridization, expression of the CCK(A) and (B) receptors (Rs), as well as of CCK itself, was studied in the normal nodose ganglion (NG), and after vagotomy, starvation and high-fat diet. CCK(A)-R mRNA expression in dorsal root ganglia (DRGs) was also explored. In the NG, 33% of the neuron profiles (NPs) contained CCK(A)-R mRNA and in 9% we observed CCK(B)-R mRNA. CCK mRNA was not found in normal NGs. Peripheral vagotomy decreased the number of CCK(A)-R mRNA-expressing NPs, dramatically increased the number of CCK(B)-R mRNA, and induced CCK mRNA and preproCCK-like immunoreactivity in nodose NPs. No significant differences in the number of NPs labelled for either mRNA species were detected following 48 h food deprivation or in rats fed a high-fat content diet. In DRGs, 10% of the NPs expressed CCK(A)-R mRNA, a number that was not affected by either axotomy or inflammation. This cell population was distinct from neurons expressing calcitonin gene-related peptide mRNA. These results demonstrate that the CCK(A)-R is expressed by both viscero- and somatosensory primary sensory neurons, supporting a role for this receptor as a mediator both of CCK-induced satiety and in sensory processing at the spinal level. The stimulation of CCK and CCK(B)-R gene expression following vagotomy suggests a possible involvement in the response to injury for these molecules.