These are cells that can be found throughout the brain, like in the cortex, hippocampus, and amygdala. They are excitatory cells (vs. inhibitory), meaning they tend to make the neurons receiving its signals more likely to release neurotransmitters (“excited”). Pyramidal neurons can differ a bit in shape and this is thought to represent different subtypes. And because there are so many of them throughout the brain spanning areas related to many different functions, the roles of these cells can’t be neatly defined.
Anyway, I recently heard about how certain manipulations of the excitatory pyramidal cells may make them an inhibitory cell. Neurotransmitter switching! Although this was my first time hearing about it, the idea isn’t that new [1]. We take it for granted that the identity of neurons are very stable; when I talked to some people about neurotransmitter switching and they were either amazed and surprised or reluctant to believe it. Specifically for excitatory to inhibitory neurotransmitter switching, their dismissal is reasonable given that the required internal change (different proteins will need to be expressed) seems rather substantial. Additionally, the neuron’s structural change (inhibitory and excitatory neurons have slightly different shapes) and the surrounding structural changes (cells receiving input from a changing cell will also have to react) all just makes this process unreasonable. But neurons in a petri dish act differently, depending on its environment, including switching neurotransmitters[2] and changing channel expressions [3]. There’s also evidence that some neurons switch neurotransmitters during development [4]! So maybe this change isn’t so improbable?
Regardless, if drastic switching is real, then our brain is much more plastic than we generally imagine them to be. While this can be reassuring (the brain may adapt to various insults), it is also a bit scary (can it be maladaptive, say after chronic drug use?).
[1] PMID: 26050033
[2] PMID: 3009730*
[3] PMID: 14751586
[4] PMID: 21123581
*The author, DD Potter, is also known for his beautiful “microcultures” images showing that a single cell will synapse onto itself
Originally posted on Instagram October 31, 2019
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