INTERLEUKIN-6 AFFECTS SCOPOLAMINE-INDUCED AMNESIA, BUT NOT BRAIN AMINO-ACID LEVELS IN MICE

WE have previously shown that, after peripheral administration, differ ent cytokines affect cognitive functions in mice. In this study, we ev aluated the effects of mouse interleukin-6 (IL-6) on the classical beh avioural test of scopolamine-induced amnesia for a passive avoidance r esponse in the mouse. Pretraining i.p. administration of this cytokine (0.125 and 0.5 mu g/mouse) significantly reduced the amnesic action o f the muscarinic receptor antagonist. As it is well known that brain a mino acids are deeply involved in the modulation of cognitive processe s we measured the levels of glutamine, aspartic acid, glutamic acid an d GABA in the hippocampus and hypothalamus of mice treated with IL-6. At both doses which affected the cognitive functions, this cytokine ha d no effect on brain levels of measured amino acids. Neither nocicepti ve thresholds to a thermal stimulus, nor spontaneous locomotor activit y were modified by the acute administration of IL-6 (0.5 mu g/mouse). Our data confirm previous observations indicating that peripheral admi nistration of cytokines affects some, but not other brain functions an d suggest the involvement of IL-6 in the central modifications induced by the immune activation.