Neuropeptide Y

Where it comes from

Made in

The arcuate nucleus (with AgRP), many other brain regions, and sympathetic nerves, where it is packed with noradrenaline

Sent out by

Fasting and ghrelin in the hypothalamus; leptin and insulin suppress it; stress and heavy exertion from sympathetic nerves

Acts on

• Paraventricular nucleus (feeding)
• Amygdala and hippocampus (anxiety)
• Blood vessels (constriction)
• Bone and fat

What it does

• Drives eating: injected into the hypothalamus it makes a sated rat eat
• Buffers stress; people with more of it are more resilient, and it is low in PTSD ¹
• Constricts vessels and promotes fat storage when released from sympathetic nerves

In medicine

• No medicine. Y5 blockers were trialled for obesity: a year-long trial in 1,661 people found no useful weight loss, and the class was abandoned ²
• Blood and spinal fluid NPY are research measurements in post-traumatic stress disorder, depression and heart failure, not tests anyone is offered ¹

Beyond the body’s own use

• Intranasal NPY has reached people in post-traumatic stress disorder: a single-dose study in 26 patients found it tolerated up to 9.6 mg, with a dose-related fall in anxiety after a trauma script ³
• In major depression a trial of 30 people given one intranasal dose missed its main mark at 48 hours while showing a difference at 24 hours; neither condition has had a larger trial since ⁴
• NPY itself is not approved anywhere and is not one of the peptides people obtain outside medicine. What is being asked of it is whether the brain receptors can be reached without also constricting blood vessels, which is what the sympathetic nerves use it for ¹