Analgesic actions of dynorphin A(1-13) antiserum in the rat brain stem.

This study was performed to evaluate the effects of dynorphin A(1-3) antiserum when microinjected into an active hyperalgesic region within the rat brain stem. When administered within the dorsal posterior mesencephalic tegmentum (DPMT) of intact conscious rats, dynorphin A(1-13) antiserum produced rapid onset and persistent prolongation of a low intensity thermally evoked tail avoidance response (LITETAR). These analgesic actions of the dynorphin A(1-13) antiserum appeared to be dose dependent. These studies support previous hypotheses about the existence of tonically active brain stem opioid hyperalgesic process. Further, the results provide indirect evidence for a potential role of brain stem dynorphin(s) in facilitating pain.