🧠 Lecture 10: Feeding, Ghrelin & Neurogenesis

What is adult hippocampal neurogenesis (AHN)?

Generation of new neurons in the dentate gyrus (DG) and SVZ (subventricular zone) of the adult brain.

• Important for:

  • Memory

  • Learning

  • Pattern separation (e.g. distinguishing similar locations)

What factors increase vs decrease AHN??

Factors that ↑ AHN:

• Exercise

• calorie restriction

• environmental enrichment

• antidepressants

Factors that ↓ AHN:

• Aging

• Stress

• Depression

• Dementia

How does calorie restriction affect neurogenesis?

Increases hippocampal neurogenesis and memory, possibly via ghrelin.

What is ghrelin and what does it do?

28 amino acid peptide, produced by stomach.

• Two forms:

  • Acyl-ghrelin (AG): Active form, binds GHSR1a receptor.

  • Unacylated ghrelin (UAG): Inactive unless converted.

• Regulates:

  • Growth hormone release

  • Appetite

  • Memory and neurogenesis

How does unacylated ghrelin (UAG) affect AHN?

UAG reduces cell proliferation and impairs hippocampal neurogenesis and memory

Whta is the link between Ghrelin & AHN?

• Acyl-ghrelin (AG) promotes neurogenesis and memory (especially pattern separation).

• GHSR (ghrelin receptor) found in mature neurons in DG but not in stem cells.

• AG enhances AHN in rats (via BrdU studies).

• UAG impairs AHN → reduces Ki67 and DCX cells.