Neuronally induced augmentation of cardiac output

Area of Science:

• Cardiovascular Physiology
• Neurocardiology

Background:

• Adrenergic stimulation influences cardiac function through direct effects on myocytes and indirect neuronal pathways.
• Understanding the specific roles of beta-adrenergic receptor subtypes in modulating cardiac output is crucial for therapeutic development.

Purpose of the Study:

• To investigate whether cardiac output can be enhanced by selectively activating cardiac adrenergic efferent neurons.
• To compare the effects of direct myocyte stimulation versus neuronal activation on cardiac output.

Main Methods:

• Anesthetized pigs received infusions of beta1-adrenoceptor agonist (dobutamine) or a selective beta2-adrenoceptor agonist (terbutaline).
• Hemodynamic parameters including heart rate and cardiac output were monitored.
• Cardiac myocyte beta-adrenoceptor expression was analyzed.

Main Results:

• Terbutaline significantly increased heart rate and cardiac output, suggesting indirect neuronal activation.
• Dobutamine increased heart rate, cardiac output, and left ventricular intramyocardial systolic pressure.
• Porcine ventricular myocytes predominantly express beta1-adrenoceptors, indicating direct myocyte stimulation by terbutaline was unlikely.

Conclusions:

• Beta2-adrenergic agonists augment cardiac output in pigs mainly through neuronally mediated increases in heart rate.
• Neuronal pathways offer a potential strategy to enhance cardiac output independently of direct ventricular augmentation.
• Further research is needed to explore neurocardiological interventions for supporting diseased myocardium.