Abstract: Unilateral microinjection of CaCl₂ or MgCl₂ (10 nmol) into septum or nucleus accumbens of the rabbit via chronically implanted cannula markedly attenuated the analgesic effect induced by morphine or electroacupuncture (EA) stimulation. Microinjection of cation chelating agent CDTA (20 nmol) into septum or n. accumbens, on the contrary, potententiated EA and morphine analgesia. Injection into the vicinity of the nuclei was not effective. The results suggest (1) a similarity of the actions of Ca²⁺ and Mg²⁺ in antagonizing EA and morphine effect, (2) a similarity of the mechanisms for EA and morphine analgesia, and (3) the importance of septum and nucleus accumbens in mediating EA and morphine analgesia.