In vivo imaging of brain incorporation of fatty acids and of 2-deoxy-D-glucose demonstrates functional and structural neuroplastic effects of chronic unilateral visual deprivation in rats

Regional cerebral 'incorporation coefficients' k* of each of 3 labeled long-chain fatty acids -[9,10-3H]palmitate ([3H]PA), [1-14C]arachidonate ([14C]AA) and [1-14C]docosahexaenoate ([14C]DHA)-were measured using quantitative autoradiography in 11 bilateral brain visual areas of 3.5-month-old awake, hooded, Long-Evans rats, and were compared with regional cerebral metabolic rates for glucose (rCMRglc). The rats, which had undergone unilateral orbital enucleation at 15 days of age, were studied either in the dark with eyelids of the intact eye sutured, or when stimulated in a light box with the intact eye open. rCMRglc did not differ between homologous contralateral and ipsilateral visual areas in the dark or during stimulation, but was elevated bilaterally by 25% or more in many visual areas during stimulation compared with dark. Contralateral compared with ipsilateral k* was lower for each fatty acid tracer in superficial gray of the superior colliculus (in dark and during stimulation) and dorsal nucleus of lateral geniculate body (during stimulation). In the dark, k* for [3H]PA was correlated significantly with rCMRglc for the 22 visual areas studied, whereas during stimulation k* for [14C]AA was correlated with rCMRglc. These results suggest that central neuroplastic changes following chronic unilateral enucleation are accompanied by reduced incorporation of [3H]PA, [14C]AA and [14C]DHA into contralateral brain ares that normally receive crossed retinofugal fibers, and by symmetry of rCMRglc in the dark but increased bilateral symmetrical responsiveness of rCMRglc to visual stimulation of the intact eye.