Comparison of the effects of ACTH-(4-10) on medial vestibular nucleus neurons in brainstem slices from labyrinthine-intact and compensated guinea pigs.

The effects of adrenocorticotrophic hormone fragment 4-10 (ACTH-(4-10)) on single medial vestibular nucleus (MVN) neurons, in brainstem slices from guinea pigs which had undergone vestibular compensation for a previous ipsilateral surgical unilateral labyrinthectomy, were compared with those on MVN neurons in slices from labyrinthine-intact guinea pigs observed in a previous study. Although the average resting discharge of MVN neurons in slices from compensated animals was significantly higher than that for MVN neurons from labyrinthine-intact animals, the responses of the two groups of MVN neurons to ACTH-(4-10) were very similar. These results suggest that ACTH-(4-10) treatment is unlikely to accelerate behavioral recovery following unilateral labyrinthectomy (vestibular compensation) by acting on a receptor within the MVN for which sensitivity to ACTH-(4-10) changes during the compensation process.