If norepinephrine were suddenly deleted from the face of the earth, you probably wouldn’t wake up in the morning. If you did, you might not get very far from the covers. Norepinephrine is small molecule that is found in the central and peripheral nervous system and it is a master arouser. If you’ve got a problem, norepinephrine is going to help you solve it, or at least bring it to your attention. In the brain, norepinephrine helps neurons focus on important signals and disregard unimportant signals. When everybody is talking at once at the cocktail party, norepinephrine is responsible for helping you selectively listen to your hot date while tuning out all those other voices (a phenomenon known as the cocktail party effect). In a world without norepinephrine, every cocktail party would surely end in heartbreak. But of course, it takes some effort to even start a conversation in the first place. When researchers decrease levels of norepinephrine in the songbird brain, males take longer to sing to females and they put less effort into courting females (Barclay et al. 1996). So, a cocktail party without norepinephrine might not contain much of a clamor.
In the body, norepinephrine is largely responsible for the flight or fight response. It brings the body to action in the face of emergencies great and small. Without norepinephrine, you won’t be running from or fighting the tiger. But then, in a world without norepinephrine, the tiger probably wouldn’t even bother to chase you. That’s right; norepinephrine has similar effects on all mammals. The job of norepinephrine is similar in all vertebrates. So, from birds to rats to humans, norepinephrine helps to bring the important stuff in the world into focus and helps you disregard what is unimportant.
Scientists know a lot about the effects of norepinephrine on the body, brain, and behavior. We have studied its effects on physiology for decades. We have manipulated its levels in the brains of mice, rats, primates, and birds for years. We know that it gives an organism a general call to action. But, like all chemicals in the body, its effects can be both small and large, both nuanced and over-the-top, and there is much left to discover. For example, norepinephrine is also found in plants and invertebrates, where it may do things like regulate stress and immune responses. However, we know a lot less about its jobs in these groups of organisms. So, while a sudden wipe out of norepinephrine from the face of the earth would be a major problem, it would also present an opportunity to learn more the multifaceted actions of this important molecule, assuming of course, that any body could bother to crawl out of bed in the morning to take a look.
Barclay, S. R., Harding, C. F., & Waterman, S. A. (1996). Central DSP-4 treatment decreases norepinephrine levels and courtship behavior in male zebra finches. Pharmacology Biochemistry and Behavior, 53(1), 213-220.
May 16, 2016