Abstract: The antidepressant effects of 5 OSP (TRH, KTP, CHP, γDGG, and AGF) were studied with two behavior despair models in mice. Only CHP was shown to decrease the spontaneous motor activity of mice, the others almost showed no effec in open field test. TRH significantly shortened the immobility produced by tail suspension test and the persistant immobility produced by cornea electrostimulation test. This indicates that the antidepressant characteristic of TRH is very similar to amitriptyline or that amitriptyline exerts its antidepressant effect by affecting TRH in CNS.