Figure 1. Experimental design.

Volunteers arrived 1 h prior to the experiment. Thirty minutes before the injection, an intravenous cannula was inserted into the antecubital forearm vein for intermittent blood sampling and drug injection. Before and 1, 1.75, 3, 4, and 6 h after the injection blood samples (B) were collected and vital parameters were assessed. Before as well as 3 and 6 h after the injection the subjects completed mood and anxiety questionnaires (M). After the 1.75 h blood collection the n-back task was performed, and before the 3 h collection the acquisition for the long-term memory test took place. When showing no signs of inflammation or any other kind of illness, subjects were discharged and returned on the following day for follow-up examination and completing the long-term memory task. The whole procedure was repeated on another study day with a 10–14 days delay. Every participant received the higher or lower dose of LPS during one and saline during the other test session in a balanced, randomized manner.