Groups of Hindbrain GLP1 Neurons Targeting the Hypothalamus, Thalamus, or Limbic Forebrain Also Send Branches to All Brain Areas Connected to GLP1 Neurons

Glucagon-expressing neurons project to multiple brain regions and the spinal cord, revealing extensive connectivity.

• Neurons in the caudal nucleus of the solitary tract (cNTS) and intermediate reticular nucleus (IRt) both contribute to glucagon-like peptide 1 (GLP1) axon projections.
• Distinct subsets of GLP1-expressing neurons appear to have overlapping axonal projections across various brain regions.
• Cre-dependent tracing indicated that cNTS and IRt neurons show reciprocal labeling, suggesting interconnectivity between these populations.
• Microinjections into specific brain nuclei demonstrated that GLP1 neurons from both cNTS and IRt share axon collaterals in the spinal cord and other central regions.
• The collective axon collaterals from GLP1 neuron populations innervate key areas such as the thalamic paraventricular nucleus and hypothalamic paraventricular nucleus.

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