Age-Related Decreases in Colonic Neurokinin A Content and Release Monitored Using Electrochemical Immunosensors.

BACKGROUND: Aging increases the risk of bowel dysfunction and reduced quality of life. Although Neurokinin A (NKA)-mediated smooth muscle contraction declines with age, it is unclear whether this reflects altered NKA content and/or release. This study examined age-related changes in colonic NKA content and release and assessed whether changes correlated with fecal NKA. METHODS: An electrochemical immunosensor was developed and characterized for NKA detection. Distal colon tissue and fecal pellets were collected from 5- and 22-month-old female C57BL6J mice. Basal and mechanically evoked tissue NKA release was recorded in the presence and absence of ondansetron. NKA content in tissue and fecal pellets were measured. RESULTS: Sensor fabrication was validated by electrochemical and EDX analyses. The immunosensor detected NKA with a detection limit of 2.76 pM and high selectivity. Basal and mechanically evoked NKA release were significantly reduced with age. Ondansetron inhibited mechanically stimulated NKA release in 5-month-old but not 22-month-old colons. Tissue NKA content declined with age. The proportion of total NKA released decreased from 65% ± 22% in young tissue to 30% ± 23% in aged tissue. Fecal NKA levels were similarly reduced in older mice. CONCLUSIONS: Reduced NKA release with aging is associated with lower tissue content. The electrochemical immunosensor provides a simple, cost-effective method for NKA quantification and could be adapted for other gastrointestinal neuropeptides. The decrease in fecal NKA levels supports further investigation of fecal NKA as a noninvasive marker of age-related changes in bowel function.