Analysis of Correlations between Behavioral Parameters in the Elevated Plus Maze and the Levels of Interleukin-1beta in Blood Plasma in Rats

Peripheral cytokines may influence psychoemotional behavior,but the role of interleukin-1beta (IL-1beta) in altering anxietyand motor activity in response to inflammatory activation remainsunclear. To clarify this issue, correlations between behavioralparameters in the elevated plus maze (EPM) test and plasma levelsof IL-1beta after administration of the proinflammatory stimuluslipopolysaccharide (LPS) in different modes were analyzed in adultmale rats. LPS in doses of 0.5 or 5 mg/kg, as well as physiologicalsolution (control), were administered to rats intraperitoneally.The most pronounced behavioral effect 24 hours after a single injectionwas an endotoxin dose-dependent inhibition of the animals’ motoractivity. Twenty four hours after the 5 mg/kg, an increased anxietybehavior was also observed. The behavioral changes caused by thehigh dose of endotoxin were completely normalized after a week.The behavior of the animals one day after the end of repeated injectionsof LPS at a lower dose for a week (0.5 mg/kg; once every two days)also did not differ from the control. The inhibition of motor activityafter LPS could be due to an increase in the level of IL-1beta inthe blood plasma, as indicated by the identified significant negativecorrelations between IL-1beta and the corresponding behavioral parameters.No significant correlation was found between the peripheral levelof IL-1beta and such a classic indicator of anxiety as the percentageof entries into the open arms of the maze. In general, the obtainedresults allow us to conclude that IL-1beta is an undoubted participantin the mechanism of the transient inhibitory effect of LPS on motoractivity.