Neonatal chickens were injected intraventricularly with Ni(II), Pd(II), Cu(II) or Zn(II) complex of TRH and the potencies of stimulating locomotor activity were compared with that of TRH, Ni(II)-TRH was more potent than the ligand while Pd(II)-TRH was inert. Cu(II)- and Zn(II)-TRH induced the response to the same extent of the ligand. These results indicate that the action of TRH in the CNS resulting in the locomotor hyperactivity is dependent on the tertiary conformation of molecule which is modified by chelate formation.