by Athina Sitou, Contributing Writer
Why does getting a hot cup of tea or coffee make studying feel more enjoyable? Behind the warm, satisfying feeling lies caffeine’s seemingly magical ability to “wake up” our brain and boost our happiness levels.
Caffeine’s secret to creating alertness is blocking adenosine receptors, just like we grab a cup of coffee to fight off sleepiness (2). The name “adenosine” may remind one of adenosine triphosphate (ATP), the energy-carrying compound that powers our cells. In the brain, however, adenosine works on its own and actually signals the brain to slow down its activity (3). This signaling occurs throughout the brain in the spaces between neurons known as synapses. Here, neurons release substances to be received by consecutive neurons, whose plasma membranes contain specialized receptors for a variety of chemical messengers.
When drugs are not affecting our brain’s functions, adenosine will bind to its receptors, encouraging sleep through various complex mechanisms. For example, adenosine can either inhibit the activity of wakefulness-promoting neurons or activate those that induce sleep (3). Surprisingly, caffeine has a structure so similar to adenosine that it dupes adenosine receptors and binds to them in its place, preventing the molecule’s sleep-inducing effects (2).
Caffeine also creates alertness in different ways. Due to increased neuronal activity, the pituitary gland—a small organ at the base of the brain—secretes hormones that increase adrenaline production by the adrenal glands. Adrenaline’s “fight or flight” effects such as increased heart beat rate and glucose release translate as the energy jolt that we get from caffeine (1).
However, caffeine’s energizing properties alone are not what creates the feelings of satisfaction and dependency that we associate with it. Because of the convenient location of certain adenosine receptors nearby dopamine receptors, caffeine also triggers the release of dopamine.
Under normal circumstances, adenosine impedes dopamine’s activity. Caffeine’s interference ultimately enhances dopamine’s effect tied with the reward and pleasure-inducing circuit (4).
Caffeine’s mechanisms are multi-faceted and this overview briefly discusses them in an attempt to showcase the incredible interconnectedness of our brains’ inner workings. Although we thankfully do not need to understand caffeine’s molecular properties to enjoy it, studying this widely consumed substance’s action in the brain may provide helpful insights.
Edited by Laura Reumont
References:
1. Brain, M., Bryant, C. W., & Cunningham, M. (2020, January 27). How caffeine works. HowStuffWorks Science. Retrieved February 18, 2022, from https://science.howstuffworks.com/caffeine4.htm
2. Nehlig, A., Daval, J. L., & Debry, G. (1992). Caffeine and the central nervous system: mechanisms of action, biochemical, metabolic and psychostimulant effects. Brain research. Brain research reviews, 17(2), 139–170. https://doi.org/10.1016/0165-0173(92)90012-b
3. Strecker, R. E., Morairty, S., Thakkar, M. M., Porkka-Heiskanen, T., Basheer, R., Dauphin, L. J., Rainnie, D. G., Portas, C. M., Greene, R. W., & McCarley, R. W. (2000). Adenosinergic modulation of basal forebrain and preoptic/anterior hypothalamic neuronal activity in the control of behavioral state. Behavioural brain research, 115(2), 183–204. https://doi.org/10.1016/s0166-4328(00)00258-8
4. Temple J. L. (2009). Caffeine use in children: what we know, what we have left to learn, and why we should worry. Neuroscience and biobehavioral reviews, 33(6), 793–806. https://doi.org/10.1016/j.neubiorev.2009.01.001
The Abstract 