Developmental Characteristics of the Kitten Lower Esophageal Sphincter
Gastroesophageal reflux is a common finding during infancy. In the cat, in vivo LES pressure increases with age from 9.5 ± 2.4 mmHg at 3 days to 21.5 ± 2.9 mmHg at 6 weeks to 43 + 4.5 mmHg in the adult cat. In order to examine the genesis of this reduced pressure in the kitten, we determined the mechanical characteristics and responses to muscarinic stimulation of both the kitten and adult LES. Circumferentially oriented rings of the LES exhibited increased in vitro active force in response to + induced depolarization with advancing age (Figure 1). Normalizing active forces for the different amount of muscle present in the various age groups yields greater stresses in the kitten (Figure 2), suggesting that reduced LES pressures are not due to reduced contractility in the kitten. According to Laplace’s law, pressure equals the product of the stress and the ratio of the circular muscle thickness to its inner radius ratio1. In the kitten thickness/radius ratio is such that despite higher stresses generated, lower pressures are developed.