ABSTRACT
Electrophysiological studies recording the impulse activity in single fibers have shown that visceral afferents respond to a variety of stimuli. The sensory innervation of the gastrointestinal tract is involved in reflex pathways mediated through the central nervous system and spinal cord that regulate motility and transit, secretion, absorption and blood flow. Numerous peptide have been demonstrated in the capsaicin-sensitive innervation of the skin including substance P and the related tachykinins, calcitonin gene-related peptide, somatostatin, vasoactive intestinal peptide. Visceral afferents with fibers in the vagus nerve transmit information to the central nervous system from receptors located in the muscle and mucosa. Receptors sensitive to stimuli applied to the visceral lumen have been described throughout the gastrointestinal tract. Inhibition of gastrointestinal transit by peritoneal irritation with an iodine solution abolished by ablation of the visceral sensory innervation. Circulating cholecystokinin also inhibits gastric motility and emptying by a vagal capsaicin-sensitive pathway in the rat.
