Descending inhibitions from the nucleus raphe magnus and adjacent reticular formation to the dorsal horn of the rat are not antagonized by bicuculline or strychnine.

The effects of iontophoretically applied bicuculline and strychnine on brainstem-and segmental-evoked inhibitions of dorsal horn cells have been examined in the rat. Both antagonists failed to reduce the descending inhibitory influences at concentrations which selectively blocked responses to GABA or glycine and segmentally-derived inhibitions of the same neurones. These results suggest that neither GABA nor glycine is involved in brainstem inhibition of rat dorsal horn cells.