One day, as a neuroscience undergraduate, I took my seat in a lecture corridor, pulled out my laptop computer and ready for one more day of studying concerning the fascinating organ that’s the mind. Without any prior warning, the lecturer plugged in his laptop system and Dion DiMucci’s “The Wanderer” started to play.

As the lyrics “Oh well, I’m the type of guy who will never settle down” echoed by means of the lecture corridor of scholars, our heads turned to one another for reassurance that our confusion was shared. “Today,” the lecturer began, “we’re covering the vagus nerve.”

Fifty minutes later, the confusion had lifted. We discovered how “vagus” means “wandering” in Latin, an apt identify for a nerve that takes an in depth, winding path by means of the physique.

The vagus nerve performs an essential perform within the department of the human nervous system referred to as the parasympathetic nervous system (PNS), usually nicknamed the “rest and digest” system.

The vagus nerve’s position within the regulation of processes reminiscent of coronary heart price, respiration, immune responses and the digestive system has been extensively studied. Now, Physiology Associate Professor Rohit Ramchandra and colleagues on the University of Auckland not too long ago found a novel perform for the “wanderer”, in train. Their examine is printed in Circulation Research.

The “wanderer” – inactive throughout train?

Vagal nerve exercise in train is “understudied” and “controversial”, according to Ramchandra and colleagues.

For a few years scientists, firmly believed that the sympathetic nervous system, usually nicknamed “the fight or flight” system, is in overdrive throughout train. This helps the guts to beat sooner, pumping a lot wanted blood and oxygen across the physique. In distinction, PNS exercise was assumed to dial down or turn out to be utterly absent throughout train. “Historically, no role for the PNS during exercise has been concluded due to the assumption that cardiac vagal nerve fibers only innervate the sinoatrial node (SAN) and the absence of changes in cardiac function with cholinergic blockers,” the researchers write.

Ramchandra and colleagues examined the speculation that cardiac vagal exercise is definitely elevated throughout train, and that denervation of the cardiac vagal department would scale back coronary heart perform. They connected electrical recording units to observe cardiac vagal nerve exercise (CVNA) in sheep throughout train. Sheep have comparable cardiac anatomy and physiology to people, and they’re usually utilized in laboratory experiments exploring coronary heart illness.

Cardiac vagal nerve exercise elevated throughout train

“Our group has used ‘tour de force’ electrical recording techniques to directly monitor vagal nerve activity in exercising sheep and has found the activity in these vagal nerves going to the heart increases during exercise,” says Ramchandra.

An improve in CVNA occurred through the initiation of train, which then plateaued because the depth elevated.

“Our study finds the activity in these ‘rest and digest’ vagal nerves actually increases during exercise,” Ramchandra says.

When the researchers denervated the left cardiac vagal department, cardiac perform was impaired whereas the sheep exercised. This helped the staff to show a speculation relating to the position of acetylcholine in train. “The cardiac vagus nerve releases multiple mediators, and previous research has focused on a neurotransmitter, acetylcholine, which has no impact on our ability to exercise,” says Ramchandra.

The researchers blocked acetylcholine receptors pharmacologically whereas the sheep exercised, and located it had no influence on cardiac perform. “Taken together with the vagal denervation data, this finding suggests a separate mechanism for the effects of CVNA during exercise beyond acetylcholine-mediated signaling,” they explain.

Ramchandra and colleagues turned their consideration to a unique meditator – vasoactive intestinal peptide (VIP). They discovered that VIP was launched by the vagus nerve throughout train. This “helps the coronary vessels dilate, allowing more blood to pump through the heart,” says Ramchandra.

“For the heart to sustain a high level of pumping, it needs a greater blood flow during exercise to fuel the increased work it is doing: our data indicate that the increase in vagal activity does just this.”

Improving train tolerance in coronary heart failure sufferers

A limitation of the examine, acknowledged by the researchers, is that solely feminine sheep have been examined. “While we anticipate the observations made in this study will be applicable to males, this will need to be tested in future studies,” Ramchandra and colleagues say.

The researchers’ follow-up examine will discover whether or not this perform of cardiac vagal nerves will be utilized to assist coronary heart failure sufferers enhance their train tolerance. “This inability to carry out simple tasks involving exertion means that quality of life is severely compromised in these patients,” explains Ramchandra. “One potential reason why exercise tolerance is reduced is that the diseased heart simply does not receive enough blood.”

Reference: Shanks J, Pachen M, Chang JWH, George B, Ramchandra R. Cardiac vagal nerve exercise will increase throughout train to reinforce coronary blood stream. Circ. Res. 2023;133(7):559-571. doi: 10.1161/CIRCRESAHA.123.323017