Asymmetry in behavioral responses to cholecystokinin microinjected into rat nucleus accumbens and amygdala

The behavioral responses of rats to uni- or bilateral microinjections of the octapeptide cholecystokinin (CCK-8) into the left and/or right or both nucleus accumbens (NA) or amygdalae were studied. There were two main findings of effects of microinjections of CCK-8 into NA. First, bilateral injections of CCK-8 into NA dose-dependently decreased the horizontal activity. The second more important finding was that CCK-8 at a specific dose (0.01 micrograms) injected into the right NA increased the number of horizontal movements 6-fold as compared to the injection into the left NA. Neither uni- nor bilateral injections of CCK-8 into NA at all doses used induced changes in the vertical movements. CCK-8 injected into left, right or both amigdalae increased locomotion at the lowest dose (0.01 microgram), while at the high doses (0.5 and 1.0 microgram) it significantly decreased it. The plus-maze test confirmed the anxiogenic effect of CCK-8 (0.01 microgram) injected into amigdalae. CCK-8 exerted a favorable effect on learning and memory (shuttle-box) when injected into the left but not into the right amygdala. Injection of CCK-8 (0.01 micrograms) into left amygdala provoked a 4-fold increase of the number of avoidances as compared to the microinjection into the right amygdala.