Decrease in participation of nitric oxide in nonadrenergic, noncholinergic relaxation of rat intestine with age

Area of Science:

• Gastroenterology
• Neuroscience
• Physiology

Background:

• Nonadrenergic, noncholinergic (NANC) neurotransmission mediates intestinal relaxation.
• Nitric oxide (NO) is a key mediator in the enteric nervous system.
• The age-dependent role of NO in intestinal NANC relaxation requires further elucidation.

Purpose of the Study:

• To investigate the age-related changes in the participation of nitric oxide (NO) in electrical field stimulation (EFS)-induced NANC relaxation in different regions of the rat intestine.
• To assess the sensitivity to exogenous NO and the expression of nitric oxide synthase (NOS) in relation to age.

Main Methods:

• Electrical field stimulation (EFS) was used to induce NANC relaxation in isolated intestinal segments from Wistar rats of varying ages (2-50 weeks).
• The contribution of NO to relaxation was assessed using pharmacological inhibitors.
• Sensitivity to exogenous NO and immunohistochemical localization of NOS were evaluated.

Main Results:

• The NO-mediated component of NANC relaxation was prominent in young rats (2-4 weeks) but significantly decreased or was absent in older rats (8-50 weeks) in the jejunum, ileum, colon, and rectum.
• Younger rats exhibited higher sensitivity to exogenous NO in the jejunum and proximal colon.
• Immunoreactive nitric oxide synthase (NOS) structures were observed in the rectal circular muscle, with denser populations in younger rats.

Conclusions:

• Nitric oxide is the primary mediator of NANC intestinal relaxation in young rats, with its significance diminishing rapidly with age.
• Age-related decline in NO signaling contributes to altered intestinal motility in adult rats.
• These findings highlight the critical role of NO in maintaining intestinal function throughout development.