Imagine you are eating a delicious slice of chocolate cake. You may feel happy inside just thinking about it - you don’t even need to see, smell, or taste the cake. How does your brain create this effect? There are neurons in your brain which produce a neurotransmitter (a chemical messenger that neurons use to communicate with each other) called dopamine. High levels of dopamine make us feel good. When you think of the cake, neurons in your brain release dopamine, which relays a message to other neurons to tell your body to feel happy. This is called a reward response: it helps us to learn and remember things in our environment that we like . To better understand how dopamine-producing neurons regulate the reward response, researchers can look to the fruit fly as a model system. In the latest issue of Current Biology, Rohwedder et al. identified a novel set of dopamine-producing neurons in the larval brain which appear to connect with neurons of the mushroom body, a known center for learning and memory in the fly . By expressing genes in these neurons that either killed them or caused them to become active, they showed that depending on where these dopamine-producing neurons contact the mushroom body, this results in a reward response to a different type of sugar. This novel set of neurons behaves in stark contrast to a previously described set of dopamine-producing neurons, which are known to be important for aversive behaviors (for instance, when you spit something out because it tastes awful). Identification of distinct sets of neurons that regulate reward versus aversion is a common feature observed in adult fruit flies and in mammals, but until now has never been observed in developing individual neurons. This study lays the groundwork for the possibility of studying in great detail the reward-aversion behavioral paradigm at the level of single neurons.
Jennifer Lovick (@drjkyl)
Senior Editor, Science in Entertainment, Signal to Noise
PhD, Molecular, Cell, and Developmental Biology
1. “Dopamine Is __________ Is it love? Gambling? Reward? Addiction?” Bethany Brookshire for Slate. July 3 2013. www.slate.com/articles/health_and_science/science/2013/07/what_is_dopamine_love_lust_sex_addiction_gambling_motivation_reward.html
2. Rohwedder A, Wenz NL, Stehle B, Huser A, Yamagata N, Zlatic M, Truman JW, Tanimoto H, Saumweber T, Gerber B, Thum AS. Four individually identified paired dopamine neurons signal reward in larval Drosophila. Curr Biol. 26, 661-669 (2016). DOI: dx.doi.org/10.1016/j.cub.2016.01.012