New heterocyclic ring systems. Synthesis and pharmacological activity of 6H-1,3,4-thiadiazolo [3’,2’: 1,2]-5-oxopyrimido[5,4-b]indole derivatives and of 1-phenyl-6H-1,2,4-Triazolo [1’,5’: 1,2]-5-oxopyrimido [5,4-b]Indole