Multiple neurochemical and hormonal mechanisms of stress-induced analgesia.

The principal theme of our work on the phenomenon of stress-induced analgesia has been that multiple neurochemically and neurohormonally discrete paininhibitory systems exist and that these systems can be selectively activated by a single stressor, inescapable footshock. Some of these stress-activated endogenous mechanisms of analgesia involve opioid peptides, others do not. Similarly, some forms of stress analgesia rely principally on central nervous system substrates, but others are dependent upon hormonal factors, possibly opioid peptides, as well. This chapter describes our initial investigations identifying these various forms of stress analgesia, highlights some of the evidence indicating the independence of these multiple forms, and attempts to integrate some of our findings with those reported by others.