4.5. Forced swim test
Thirty minutes after the ICV administration, half of the mice (N=36) were evaluated for depression-like behavior in a forced swim test for 5 min. Half of these mice were tested on the 8th day and the other half on the 9th day. The apparatus, described originally by Porsolt et al. (1977), consists of a plexiglass cylinder of 200 mm height and 120 mm diameter, containing 1.5 l of water. Each mouse was dropped individually into the water, maintained at 25 ± 1 °C. The principle of the test is that in such a situation, from which they cannot escape, animals rapidly became immobile, that is, floating in an upright position and making only small movements to keep their heads above water. In parallel, their attempt to escape the cylinder by climbing or swimming may decrease or cease eventually. For 5 min period the following parameters were recorded by an observer sitting at 1 m distance from the center of the plus-maze: 1. the climbing activity (the time that mice spent with climbing the walls, in their attempt to escape the cylinder), 2. the swimming activity (the time that mice spent with swimming in the water, in their attempt to remain at the surface) and 3. the time of immobilization (the time that mice spent in an upright position on the surface with its front paws together). A 5 s period was considered a time unit, therefore the activity and the immobility were expressed in time units.
