The effect of insulin and insulin-like growth factors on hippocampus- and amygdala-dependent long-term memory formation

Learn Mem. 2014 Sep 16;21(10):556-63. doi: 10.1101/lm.029348.112. Print 2014 Oct.

Abstract

Recent work has reported that the insulin-like growth factor 2 (IGF2) promotes memory enhancement. Furthermore, impaired insulin or IGF1 functions have been suggested to play a role in the pathogenesis of neurodegeneration and cognitive impairments, hence implicating the insulin/IGF system as an important target for cognitive enhancement and/or the development of novel treatments against cognitive disorders. Here, we tested the effect of intracerebral injections of IGF1, IGF2, or insulin on memory consolidation and persistence in rats. We found that a bilateral injection of insulin into the dorsal hippocampus transiently enhances hippocampal-dependent memory and an injection of IGF1 has no effect. None of the three peptides injected into the amygdala affected memories critically engaging this region. Together with previous data on IGF2, these results indicate that IGF2 produces the most potent and persistent effect as a memory enhancer on hippocampal-dependent memories. We suggest that the memory-enhancing effects of insulin and IGF2 are likely mediated by distinct mechanisms.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Amygdala / drug effects*
  • Animals
  • Avoidance Learning / drug effects
  • Conditioning, Psychological / drug effects
  • Fear / drug effects
  • Hippocampus / drug effects*
  • Insulin / pharmacology*
  • Insulin-Like Growth Factor I / pharmacology*
  • Insulin-Like Growth Factor II / pharmacology*
  • Male
  • Memory, Long-Term / drug effects*
  • Nootropic Agents / pharmacology*
  • Rats
  • Rats, Long-Evans

Substances

  • Insulin
  • Nootropic Agents
  • Insulin-Like Growth Factor I
  • Insulin-Like Growth Factor II