Localized metabolic responses to optokinetic stimulation in the brain stem nuclei and the cerebellum investigated with the [ 14C]2-deoxyglucose method in rats

Abstract

The localized metabolic effects of monocular optokinetic stimulation to the cerebellar flocculus and brain stem nuclei were measured in pigmented rats. Quantitative [ 14C]2-deoxyglucose autoradiography was performed on alert rats stimulated with a drum either rotated horizontally in the temporonasal direction (optokinetic group) or kept stationary (control group). The superior colliculus in both groups showed a higher amount of activity on the contralateral side to the stimulated eye than on the ipsilateral side. The dorsal cap of the inferior olive, the nucleus of the optic tract, and the lateral pontine nucleus showed a higher amount of activity on the contralateral side only in the optokinetic group. The nucleus reticularis tegmenti pontis and the ventromedial aspect of the cerebellar paraflocculus showed no lateralized activity in either group. Local glucose utilization rates of both flocculi were significantly enhanced in the optokinetic group. Only in the optokinetic group did the ipsilateral flocculus show a higher local glucose utilization rate than the contralateral flocculus. The most enhanced activity was localized in the middle aspect of the rostrocaudal extent of the ipsilateral flocculus. The activity was greater in the granular layer than in the molecular layer or in the white matter. The pattern of activation in the granular layer was characterized by a patchy appearance in the frontal sections. Serial reconstruction of these sections showed metabolic blobs appearing with intervals of several hundred micrometers.