Analgesic effect of novel organogermanium compound, GE-132

A novel organogermanium compound, Ge-132, carboxyethylgermanium sesquioxide, showed enhancement of 0.5 mg/kg morphine analgesia in both administration routes of oral administration (p.o.) and intraperitoneal injection (i.p.) in the Tail-Flick test, and the effect was completely abolished by 0.5 mg/kg Naloxone, stereospecific opiate antagonist. Ge-132 alone, 250 mg/kg i.p., did not show any antinociceptive action by assessing the Tail-Flick test and the Hot-Plate test. By the intracerebral injection of Ge-132, 100-1000 micrograms, prolongation of Tail-Flick latency was observed and the action was abolished by 50 micrograms CaCl2 injection. Although bestatin which is reported to enhance the morphine analgesia inhibits enkephalinase and enkephalin aminopeptidase, Ge-132 did not show any inhibition on both enkephalin degrading enzymes. The possibility for the mode of action of Ge-132 was discussed.