Pharmacological studies on the effect of serotonin centrally Administered in Rabbits

The effects of interacerebroventriculary administered sero- tonin (100ug, 200 ug ) and serotonin antagonists represented by cyproheptadine (150 ug, 300ug ) or methysergide (200ug, 400ug ) alone and of serotonin after cyproheptadine or methysergide in two dose levels were investigated. Studies were carried on blood pressure . heart rate , ECG pattern , body temperature , and calcium in seru, heart and brain tissues of contentents of nnorepinephirne and dobamine were also determined in usikg high dose levels only . The findings of this investigation can be summarized as follows .Effects on blood pressure :Administration of serotonin induced significani reduction in blood pressure in adose dependent manner in conscious rabbits .Cyproheptadine alone did not cause any alteration , but prior to serotonin it antagonisedthe lowing effect of serotonin in the two dose levels . Methysergide alone signicantly reduced the blood pressure and potentiated serotonin lowering effect on blood pressure when given either in low or high doses prior to itEffects on heart rate :Serotonin significantly reduced the heart rate of cons – cious rabbits in the two dose levels . Cyproheptadine did not