High blood pressure can be caused by a tiny organ similar to a thermostat that senses oxygen levels in the blood, research has shown.

A pair of carotid bodies, each no bigger than a grain of rice, are located on either side of the throat between two major arteries that feed blood to the brain.

Trial patients who agreed to have one of the small clusters of sensory cells removed experienced an immediate and sustained fall in blood pressure.

Scientists believe blood pressure can rise when the carotid body "thermostat" is set too high. The findings suggest that targeting the carotid body could provide an effective new treatment for high blood pressure, known as hypertension.

Lead researcher Professor Julian Paton, from the University of Bristol, said: "Treating the carotid body is a novel approach and a potential game changer, as we believe we are reducing one of the main causes for hypertension in many patients.

"High blood pressure treatment typically tackles the symptoms targeting the end organs such as the heart, kidneys and blood vessels, and not the causes."

In a pilot safety trial, the researchers surgically removed one carotid body from a small group of 15 patients with hypertension.

Those who responded were shown to have naturally raised carotid body activity. They breathed more at rest, and produced an exaggerated breathing response when oxygen levels in their blood were lowered.

The normal job of the carotid bodies is to "sniff" levels of oxygen in blood and sound the alarm when they fall too low, signalling the brain to increase breathing rate and blood pressure.

Dr Angus Nightingale, another member of the team from the Bristol Heart Institute, said: "The falls in blood pressure we have seen are impressive - more than you would see with pharmacological medication - and demonstrate the exciting potential there now is for targeting the carotid body to treat hypertension."

Using a drug to dampen down carotid body activity would be a more practical form of treatment than surgery, the scientists pointed out.

Hopes of finding such a way to reset the carotid body "thermostat" while allowing it to function normally in emergencies have been raised by recent animal studies shedding light on how the organ works.

Prof Paton added: "This approach may lead us to the first novel anti-hypertensive treatment strategy in more than 15 years."

The research is reported in the American College of Cardiology journal Basic to Translational Science.

Professor Jeremy Pearson, associate medical director at the British Heart Foundation, which funded the research, said: "High blood pressure affects around 30% of UK adults and can lead to fatal heart attacks and stroke.

"We urgently need to find new and better ways to treat high blood pressure and that will be only possible through research.

"By tackling the problem differently and seeking to understand the underlying causes of increased blood pressure, this BHF-funded research team has shown for the first time that removal of the carotid body can effectively reduce blood pressure in patients with resistant hypertension.

"This proof of principle clinical study is the exciting first stage in developing less invasive methods or new drugs targeting the carotid body, which can be used in future to treat patients whose blood pressure is not controlled with current medication."