Effects of N-terminal nociceptin fragment on the anxiety level of American cockroach Periplaneta americana in the “open field” during changes in light intensity

Abstract

Injection of N-terminal nociceptin fragment (FN) had an anxiolytic effect on the anxiety level of the cockroach Periplaneta americana during the “open field” test in both red light and varying light. The intensity of horizontal activity (HA) and number of changes in direction (CD) by insects were taken as an indicator of their anxiety level. FN decreased HA in red light to 48% (100 μg/g) and 63% (200 μg/g) with CD of 39% (100 μg/g) relative to control. Tetrapeptide at a dose of 50 μg/g had no significant effect on HA and CD. With the light stimulus increased to 6.0 W, HA and CD reached 230% and 192%, respectively, relative to control. In this case, FN injection inhibited further HA increase in bright light to 37% (100 μg/g) and 50% (200 μg/g). CD also reduced to 39% (100 μg/g) and 68% (200 μg/g) relative to control.