A Blunted Sympathetic Function and an Enhanced Nitrergic Activity Contribute to Reduce Mesenteric Resistance in...

Area of Science:

• Physiology
• Vascular Biology
• Endocrinology

Background:

• Hyperthyroidism is associated with altered cardiovascular function.
• The role of mesenteric innervation in hyperthyroidism-induced vascular changes is not fully understood.

Purpose of the Study:

• To investigate the impact of experimental hyperthyroidism on sympathetic and nitrergic nerve function in rat mesenteric arteries.

Main Methods:

• An experimental hyperthyroidism model was established in Wistar rats using L-Thyroxine infusion.
• Electrical field stimulation (EFS) was used to assess vasoconstriction in superior mesenteric artery segments.
• The effects of alpha-adrenoceptor and purinergic receptor antagonists, and nitric oxide synthase (NOS) inhibitors were evaluated.
• Levels of neurotransmitters and key enzymes involved in sympathetic and NO pathways were measured.

Main Results:

• Hyperthyroid rats exhibited reduced body weight gain, lower adipose tissue, and increased systolic blood pressure.
• EFS-induced vasoconstriction was diminished in hyperthyroid arteries, with reduced noradrenaline release and sympathetic markers.
• Nitric oxide (NO) release was enhanced in hyperthyroid rats, linked to increased neuronal NOS activity.
• PKC and PI3K-AKT signaling pathways appeared hyperactivated, potentially mediating increased NO release.

Conclusions:

• Experimental hyperthyroidism significantly alters mesenteric innervation, decreasing sympathetic neurotransmission while increasing nitric oxide production.
• These neurovascular adaptations in the mesentery may contribute to the reduced vascular resistance observed in hyperthyroid conditions.