Dopaminergic mushroom body neurons in Drosophila: Flexibility of neuron identity in a model organism?
The study examines the general validity of Dale's principle, which states that one neuron generates one neurotransmitter.
Fig.: Dopaminergic neurons in the Drosophila brain (Vogt et al., 2014). A, B - Visualization of two main sets of dopaminergic cells projecting to the mushroom body (PAM and PPL1 clusters), dashed line - the position of the mushroom body, scale bars - 50 μm, C - scheme of basic bidirectional modulation of reward / punishment value by different groups of dopaminergic neurons in the mushroom body and formation of appetitive /aversive memories in associative learning. CA - calyx of mushroom body, PN - projection neurons, PAM - protocerebral anterior medial cluster, PPL1 - protocerebral posterior lateral 1 cluster.
In classical neuroscience, Dale´s principle postulates that neuronal identity is conferred by the specific neurotransmitter that it releases. However, the brain might be more tractable to specific situations regardless of specific specialisation which may contradict this principle. Hence, this constrained approach of how we perceive and study the nervous system must be revisited and revised, specifically by studying the dopaminergic system. We presume a relatively flexible change in the dopaminergic system due to neuronal activity or environmental changes. While the parallel between the reward system of mammals and insects is generally well accepted, herein, we extend the idea that the insect nervous system might also possess incredible plasticity, similar to the mammalian system. In this review, we critically evaluate the available information about the reward system in vertebrates and invertebrates, emphasising the dopaminergic neuronal plasticity, a challenge to the classical Dale’s principle. Thus, neurotransmitter switching significantly disrupts the static idea of neural network organisation and suggests greater possibilities for a dynamic response to the current life context of organisms.
Dvořáček J., Bednářová A., Krishnan N. and Kodrík D. (2022) Dopaminergic mushroom body neurons in Drosophila: flexibility of neuron identity in a model organism. Neurosci. Biobehav. Rev. 135: 104570 DOI: 10.1016/j.neubiorev.2022.104570