Decreased vascular sensitivity to norepinephrine following exercise training

Area of Science:

• Physiology
• Pharmacology
• Exercise Science

Background:

• Regular exercise is known to influence cardiovascular function.
• Adrenergic receptors play a critical role in regulating blood pressure and vascular tone.

Purpose of the Study:

• To investigate the effects of endurance exercise training on adrenergic receptor sensitivity in rats.
• To determine if exercise training alters the pressor response to norepinephrine in vivo and in vitro.

Main Methods:

• Adult male Sprague-Dawley rats underwent 6 weeks of swimming exercise with tail weights.
• Mean arterial blood pressure responses to intravenous norepinephrine were measured.
• Norepinephrine-induced vasoconstriction of cremaster muscle arterioles and venules was assessed using television microscopy.

Main Results:

• Exercise training significantly decreased blood pressure sensitivity to norepinephrine (pD2: 5.64 vs. 5.20).
• Arteriole sensitivity to norepinephrine in the cremaster muscle was also significantly reduced (pD2: 6.69 vs. 5.96).
• Maximal pressor responses and vessel constrictions were unaffected by exercise training.

Conclusions:

• Exercise training in rats leads to decreased sensitivity to norepinephrine.
• These findings suggest exercise training may alter alpha- or beta-adrenergic receptor function.