Differential effects of beta-carbolines and antidepressants on rat exploratory activity in the elevated zero-maze

Present experiments were designed to compare the effects of antidepressants desipramine (10 and 20 mg/kg IP) and fluoxetine (5 and 10 mg/kg IP) with a nxiogenic beta-carboline DMCM (0.5 and 1.0 mg/kg IP) in the elevated zero-m aze test in rats. The second aim of this study was to assess the effects of pinoline (6-methoxy-1,2,3,4-tetrahydro-beta-carboline) in the rat elevated zero-maze test in comparison with structurally unrelated P-carboline DMCM and antidepressants. The time spent in the open part of the elevated zero-m aze was not significantly affected by antidepressants, but was decreased by beta-carbolines pinoline and DMCM. The number of line crossings in the ope n parts and the number of head dips were also decreased more by beta-carbol ines in comparison with antidepressants. Latency to enter the open part was statistically significantly increased only by DMCM. Measurement of locomot or activity in a separate experiment indicated that activity of the rats' t ime moving, distance traveled, and number of rearings were reduced by all f our drugs studied. These results demonstrate that the effects of antidepres sants in the elevated zero-maze test differ from the effects of the referen ce anxiogenic compound DMCM. The effects of pinoline and DMCM in the zero-m aze test were similar, which suggests the involvement of mechanisms other t han serotoninergic in the action of pinoline noline. (C) 2000 Elsevier Scie nce Inc.