Objective: The purpose of this study was to determine the pathway and mode of transmission of visceral stimuli by investigating the distribution of the FOS and calcitonin gene-related peptide (CGRP) proteins in the central nervous system.
Methods: Twenty-four Sprague-Dawley rats were divided into three groups: study group (n = 12), sham control group (n = 6), and normal control group (n = 6). A balloon was implanted into the stomach of the rats in the study and sham control groups. After 48 h, the rats in the study group had the stomach distended (80 mmHg) for 2 h, after which they were killed and the antrum, thoracic spinal cord and brain were isolated or dissected. The expression of Fos and CGRP in these tissues was detected immunohistochemically.
Results: FOS expression in the dorsal horn of the spinal cord, dorsal nucleus of the vagal nerve, nucleus of the solitary tract in the study rats was significantly higher than in the sham and normal controls. However, no difference was found between the three groups in FOS expression in the myenteric plexus. Similarly, gastric distention enhanced CGRP expression significantly in the spinal cord and medulla oblongata and correlated closely with FOS expression in these two areas.
Conclusions: Gastric distention can activate the limbic system, and CGRP plays an important role in the input of visceral stimuli.