Relationship of yeast-injection induced changes in brain met-enkephalin and analgesia

Subplantar injection of Brewer's yeast induces a hyperalgesia that is associated with an increase in the level of striatal Met-enkephalin (ME); there was no change in the hypothalamus of periaqueductal gray. To test the relationship between striatal ME and analgesia, naloxone (10, 3, 0.5 mg/kg, SC) or thiorphan (100 micrograms, ICV) were administered. Neither drug caused a potentiation or a reduction in the hypersensitivity. These data suggest that an increase in striatal does not result in altered pain sensitivity in this model.