Journal of Neuroscience, Vol 10, 631-640, Copyright © 1990 by Society for Neuroscience
Optokinetic stimulation increases corticotropin-releasing factor mRNA in inferior olivary neurons of rabbits
NH Barmack and WS Young 3d
Department of Ophthalmology, R. S. Dow Neurological Sciences Institute, Good Samaritan Hospital and Medical Center, Portland, Oregon 97209.
Stimulus-specific changes in levels of corticotropin-releasing factor (CRF)
mRNA in inferior olivary neurons were studied in unanesthetized rabbits.
The possible functional importance of CRF, a neuropeptide that is expressed
in all inferior olivary neurons, in cerebellar synaptic transmission was
investigated in a subpopulation of inferior olivary neurons, the caudal
dorsal cap. Previous studies have shown that unidirectional, binocular
optokinetic stimulation increases the level of discharge in neurons located
in one of the caudal dorsal caps of the inferior olive and decreases the
level of discharge in neurons in the opposite dorsal cap. We investigated
the influence of prolonged (1-144 hr), unidirectional, binocular,
optokinetic stimulus on the levels of CRF mRNA in dorsal cap neurons,
measured with the technique of hybridization histochemistry. Rabbits were
placed at the center of a cylindrical optokinetic drum that rotated at a
constant velocity of 5 deg/sec, stimulating one eye in the
posterior-to-anterior direction and the contralateral eye in the
anterior-to-posterior direction. Posterior- to-anterior stimulation of the
left eye evoked increased activity of inferior olivary neurons located in
the right caudal dorsal cap. Conversely, anterior-to-posterior stimulation
of the right eye evoked decreased activity of neurons in the left caudal
dorsal cap. The levels of CRF mRNA in dorsal cap neurons that were
activated by prolonged optokinetic stimulation were increased by a factor
of 4 to 7 after 48 hr of stimulation and by more than a factor of 10 after
144 hr of optokinetic stimulation. These optokinetically induced increases
in CRF mRNA decayed to background levels after 30 hr. Our observations
implicate CRF in visual olivocerebellar function and suggest that CRF may
play a role in the plastic control of eye movement mediated by the visual
olivocerebellar system.