Calcitonin Gene-Related Peptide: Effect on Contractile Activity and Luminal Cross-Sectional Area in the Isolated, Perfused Porcine Ileum

Abstract

Because calcitonin gene-related peptide (CGRP) is an abundant peptide in the enteric nervous system we studied the effect of intra-arterial infusions of synthetic human CGRP I in concentrations from 10-¹⁰ to 10 -⁸ mol/1 on contractile activity and luminal cross-sectional area in the isolated perfused porcine ileum, using manometry and impedance planimetry. The frequency of the basal contractile activity was 0.37 ± 0.1 contractions per minute. CGRP induced phasic contractions, which at the highest dose were superimposed on tonic contractions, as determined by measurement of luminal cross-sectional area. The frequency of contractions dose-dependently increased to approximately 10/min at 10 ⁸ mol/1 CGRP. The amplitude of contractions increased from a maximum of 35 cm H₂0 to 51 ± 3 at 5 × 10″⁹ mol/1 CGRP and 52 ± 6 cm H₂0 at 10⁻⁹ mol/1 CGRP. After the termination of CGRP infusion at the highest dose a short phase of up to 5 min with strong tonic contraction was observed. No phasic activity was detected by manometry during this phase. In conclusion, CGRP dose-dependently increased contractile activity in the pig ileum. CGRP may therefore participate in the regulation of small-intestinal motility in the pig.

Key Words:

• Enteric nervous system
• intestinal motility
• intrinsic neurons
• neuropeptides