Autonomic nervous system function in patients with functional abdominal pain. An experimental study

Area of Science:

• Neurogastroenterology
• Autonomic Nervous System Physiology
• Psychosomatic Medicine

Background:

• Functional abdominal pain (FAP) is often linked to psychological stress.
• The role of autonomic nervous system (ANS) dysfunction in FAP requires further investigation.

Purpose of the Study:

• To compare sympathetic nervous system (SNS) response to stress and basal parasympathetic neural activity in patients with FAP, healthy controls, and patients with organic abdominal pain (OAP).

Main Methods:

• Assessed SNS response via heart rate, blood pressure, and plasma catecholamines (adrenaline, noradrenaline) during a laboratory stress test (mental arithmetic).
• Measured basal parasympathetic activity using heart rate beat-to-beat variation (mean square successive differences of R-R intervals - MSSD).
• Included plasma adrenocorticotrophic hormone (ACTH) and serum cortisol to evaluate the pituitary-adrenocortical axis.

Main Results:

• Both FAP and OAP groups showed a reduced stress-induced increase in heart rate compared to healthy controls.
• Patients with FAP exhibited significantly higher basal parasympathetic activity (MSSD) than healthy and OAP groups.
• No significant changes in plasma ACTH or serum cortisol were observed in any group post-stress.

Conclusions:

• Functional abdominal pain is associated with heightened basal parasympathetic activity and a blunted sympathetic response to acute stress.
• These findings suggest a distinct autonomic nervous system profile in FAP, potentially contributing to the pathophysiology of the condition.