Capsaicin-sensitive nerves modulate reactive hyperemia in rat gut

Area of Science:

• Physiology
• Vascular Biology
• Neurogastroenterology

Background:

• Reactive hyperemia (RH) is a vascular response to restored blood flow after arterial occlusion.
• The precise mechanisms regulating intestinal RH remain incompletely understood.
• Metabolic, myogenic, and neurogenic factors have been implicated in RH.

Purpose of the Study:

• To investigate the role of sensory innervation in modulating intestinal reactive hyperemia.
• To assess the effects of capsaicin, a neurotoxin targeting sensory nerves, on RH parameters.
• To explore the influence of acute and chronic capsaicin treatment on intestinal vascular conductance and blood flow dynamics.

Main Methods:

• Anesthetized rats underwent anterior mesenteric artery occlusion for varying durations (30, 60, 120 sec).
• Blood flow velocity was measured using Doppler velocimetry; arterial pressure was monitored.
• Reactive hyperemia was quantified by changes in vascular conductance, blood volume, and duration; capsaicin and hexamethonium were used for pharmacological interventions.

Main Results:

• Acute periarterial capsaicin significantly reduced peak conductance, blood volume, and duration of RH.
• Neonatal and chronic capsaicin treatments also decreased RH parameters, including maximal conductance.
• Capsaicin treatment reduced RH duration, an effect partially reversed by hexamethonium, which also increased RH conductance and duration.

Conclusions:

• Sensory innervation plays a significant modulatory role in the regulation of intestinal reactive hyperemia.
• Disruption of sensory nerve function impacts key RH parameters.
• These findings highlight the neurovascular interactions governing gut blood flow regulation.