Role of interleukin-1 beta in impairment of contextual fear conditioning caused by social isolation.
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.
Pugh
C R
CR
Department of Psychology, University of Colorado at Boulder, 80309-0345, USA. rachal@psych.colorado.edu
Nguyen
K T
KT
Gonyea
J L
JL
Fleshner
M
M
Wakins
L R
LR
Maier
S F
SF
Rudy
J W
JW
D000161:Acoustic Stimulation; D000818:Animals; D001923:Brain Chemistry / Q000502:physiology*; D003213:Conditioning, Psychological / Q000502:physiology*; D003463:Cues; D004305:Dose-Response Relationship, Drug; D005239:Fear / Q000502:physiology* / Q000523:psychology*; D006801:Humans; D007375:Interleukin-1 / Q000008:administration & dosage / Q000378:metabolism / Q000494:pharmacology*; D017774:Long-Term Potentiation / Q000502:physiology; D008297:Male; D008845:Microinjections; D051381:Rats; D017207:Rats, Sprague-Dawley; D011994:Recombinant Proteins / Q000008:administration & dosage / Q000494:pharmacology; D012934:Social Isolation / Q000523:psychology*
D007375:Interleukin-1; D011994:Recombinant Proteins