ACTH(4-10) accelerates ocular motor recovery in the guinea pig following vestibular deafferentation

Neuropeptide hormones such as adrenocorticotropic hormone, fragment 4-10 (ACTH(4-10], have been shown to facilitate various kinds of CNS plasticity, including recovery from deafferentation of the inner ear (vestibular compensation). The purpose of the present experiment was to determine whether the rapid compensation of spontaneous nystagmus (SN), which occurs over 2-3 days post-unilateral labyrinthectomy (UL) in the guinea pig, could be accelerated by administration of ACTH(4-10). Because of the short half-life of ACTH(4-10), injections of 200 micrograms/kg i.m. were given every 4 h for 48 h post-UL, and SN was measured every 2 h for 52 h post-UL. The results were compared with SN measurements from guinea pigs which received saline injections of the same volume, at the same times. ACTH(4-10) injections were found to significantly accelerate the rate of compensation of SN following UL. This result suggests that ACTH(4-10) may be useful in facilitating compensation when the symptoms of UL are most severe, during the first 2-3 days post-UL.