EFFECTS OF BETA-ADRENOCEPTOR BLOCKER PINDOLOL, CALCIUM-ANTAGONIST VERAPAMIL AND THEIR COMBINATION ON RETENTION IN STEP-DOWN-TRAINED AND SHUTTLE-BOX-TRAINED RATS AND ON BRAIN BIOGENIC MONOAMINES

The effects of the beta-adrenoceptor blocker pindolol and the calcium antagonist verapamil administered alone or in combination on retention in step-down-and shuttle-box-trained rats and on the biogenic monoami ne levels in the frontal cortex and hippocampus were examined. The chr onic oral treatment with pindolol impaired retention in step-down-and shuttle-box-trained rats, decreasing the dopamine (DA) and noradrenali ne (NA) levels and increasing the serotonin (5-HT) levels in the corte x and hippocampus. Verapamil did not influence retention in step-down- and shuttle-box avoidance situation and the biogenic monoamine levels in the frontal cortex and hippocampus. It should, however, be noted th at the chronic oral treatment with verapamil completely abolished the retention impairing effect of pindolol, restoring to normal DA, NA and 5-HT levels. These findings might be of interest to clinical practice and suggest the necessity for using a combination of beta-blockers wi th Ca2+ antagonists in case of prolonged treatment of cardiovascular d iseases.