Acetylcholine Neurons Become Cholinergic during Three Time Windows in the Developing Mouse Brain

eNeuro. 2024 Jul 16;11(7):ENEURO.0542-23.2024. doi: 10.1523/ENEURO.0542-23.2024. Print 2024 Jul.

Abstract

Acetylcholine (ACh) neurons in the central nervous system are required for the coordination of neural network activity during higher brain functions, such as attention, learning, and memory, as well as locomotion. Disturbed cholinergic signaling has been described in many neurodevelopmental and neurodegenerative disorders. Furthermore, cotransmission of other signaling molecules, such as glutamate and GABA, with ACh has been associated with essential roles in brain function or disease. However, it is unknown when ACh neurons become cholinergic during development. Thus, understanding the timeline of how the cholinergic system develops and becomes active in the healthy brain is a crucial part of understanding brain development. To study this, we used transgenic mice to selectively label ACh neurons with tdTomato. We imaged serial sectioned brains and generated whole-brain reconstructions at different time points during pre- and postnatal development. We found three crucial time windows-two in the prenatal and one in the postnatal brain-during which most ACh neuron populations become cholinergic in the brain. We also found that cholinergic gene expression is initiated in cortical ACh interneurons, while the cerebral cortex is innervated by cholinergic projection neurons from the basal forebrain. Taken together, we show that ACh neuron populations are present and become cholinergic before postnatal day 12, which is the onset of major sensory processes, such as hearing and vision. We conclude that the birth of ACh neurons and initiation of cholinergic gene expression are temporally separated during development but highly coordinated by brain anatomical structure.

Keywords: brain development; cholinergic neurons; transgenic mice; whole-brain imaging.

MeSH terms

  • Acetylcholine* / metabolism
  • Animals
  • Brain* / growth & development
  • Brain* / metabolism
  • Cholinergic Neurons* / metabolism
  • Cholinergic Neurons* / physiology
  • Female
  • Interneurons / metabolism
  • Male
  • Mice
  • Mice, Inbred C57BL
  • Mice, Transgenic*

Substances

  • Acetylcholine