This manuscript reports the synthesis of two series of Mannich Bases 3-12 and 21-40 obtained respectively by the reaction of either 2- ethoxycarbonylindoles 1-2 or 5H-pyridazino [4,5-b]indoles 17-20 as a substrate with formalin and the appropriate $2^{circ}C$amines under the suitable Mannich conditions. fourteen of the synthesized Mannich basese were screened as antihypetensive agents in normotensive anesthetized rats. The effect of compound 4 in normotensive anesthetized dogs was also studied.