Role of interleukin-1 Beta in Impairment of Contextual Fear Conditioning Caused by Social Isolation

Behav Brain Res. 1999 Dec;106(1-2):109-18. doi: 10.1016/s0166-4328(99)00098-4.

Abstract

Isolating rats immediately after conditioning impairs contextual but not auditory-cue fear conditioning. The reported experiments examine the involvement of brain interleukin-1beta (IL-1beta) in the impairment in contextual fear conditioning caused by social isolation. As measured by the conditioned freezing response, 5 h of social isolation after conditioning, impaired contextual but not auditory-cue fear conditioning in adult male Sprague-Dawley rats. Social isolation for 1 or 3 h after conditioning also increased IL-1beta protein in the hippocampus and cerebral cortex. No differences in IL-1beta protein levels were found in the pituitary or the hypothalamus. Intracerebroventricular (ICV) IL-1 receptor antagonist (IL-1ra) given after conditioning prevented the impairment in contextual fear conditioning caused by isolation. ICV IL-1ra had no effect on auditory-cue fear conditioning in these same animals, nor did it affect the level of contextual fear conditioning displayed by home cage controls. Like isolation, ICV IL-1beta (10 or 20 ng) after conditioning also impaired contextual but not auditory-cue fear conditioning. These results suggest that increased levels of brain IL-1beta play a role in producing the impairment in contextual fear conditioning produced by social isolation. These findings also add to the generality of the idea that stressors induce IL-1beta activity in the brain and that IL-1beta may play physiological roles in the uninjured brain.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Acoustic Stimulation
  • Animals
  • Brain Chemistry / physiology*
  • Conditioning, Psychological / physiology*
  • Cues
  • Dose-Response Relationship, Drug
  • Fear / physiology*
  • Fear / psychology*
  • Humans
  • Interleukin-1 / administration & dosage
  • Interleukin-1 / metabolism
  • Interleukin-1 / pharmacology*
  • Long-Term Potentiation / physiology
  • Male
  • Microinjections
  • Rats
  • Rats, Sprague-Dawley
  • Recombinant Proteins / administration & dosage
  • Recombinant Proteins / pharmacology
  • Social Isolation / psychology*

Substances

  • Interleukin-1
  • Recombinant Proteins