Intrahippocampal infusion of interleukin-6 impairs avoidance learning in rats

AIM: To study the effect of intrahippocampal infusion of interleukin-6 (IL-6) on
active avoidance in rats and the possible involvement of nitric oxide (NO).
METHODS: Using a shuttle-box model, the effects of bilaterally intrahippocampal
infusion of IL-6 3.2, 16, and 80 ng as well as sodium nitroprusside (SNP) 400 ng
on active avoidance were studied on d 8 after administration. The levels of
nitrite as an index of NO in the hippocampus were detected using a fluorometric
assay 24 h after infusion of IL-6 3.2 or 80 ng.
RESULTS: IL-6 16 and 80 ng impaired the acquisition performance of active
avoidance by prolonging the latency of avoidance in training, but not the
retention performance in testing. IL-680 ng and SNP 400 ng also resulted in a
marked impairment in acquisition performances by decreasing the rate of
avoidance, but not in retention performances. IL-680 ng markedly elevated the
nitrite levels from 10.6 +/- 0.7 in control rats to 13.6 +/- 2.0 (nmol/g wet wt)
(P < 0.01). IL-6 3.2 ng had no effect on active avoidance nor on nitrite levels.
CONCLUSION: Intrahippocampal infusion of IL-6 impaired learning acquisition of
active avoidance in rats.