Effects of ACTH(1-24) on single unit activity in the brainstem of the rat

Central administration of corticotropin-like peptides generally blocks the analgesic action of opiate ligands, yet it is unclear whether this is due to an independent hyperalgesic action of corticotropin or to some other mechanism. Single cells in the ventromedial medulla of the anaesthetized rat were characterized as either excited by noxious stimuli or inhibited. Injections of ACTH(1-24) excited cells that were excited by noxious stimuli and inhibited cells that were inhibited by noxious stimuli. The results support an independent role for corticotropin-like peptides in pain-modulating mechanisms.