Resting and high-frequency evoked 2-deoxyglucose uptake in the rat inferior colliculus: developmental changes and effects of short-term conduction blockade.

Development of resting and high-frequency-evoked metabolic patterns in the central nucleus of the inferior colliculus (ICC) in rat was investigated using the 2-deoxyglucose (2-DG) method. The effects of early short-term acoustic deprivation were studied by unilateral blockade of the external auditory meatus on postnatal day 12. Quantitative and qualitative analyses were performed on 2-DG uptake in 5 regional sectors of ICC. Adult resting ICC uptake is robust and exhibits regional differentiation with the ventromedial region preferentially labelled. At 17 days of age, resting uptake is substantially lower and regionally more uniform than in the adult. This age-dependent change is likely a function of the immature stage of neuronal and cochlear development at 17 days. Unilateral 50 kHz stimulation in the adult results in bilaterally enhanced 2-DG incorporation in ventromedial ICC, with a discrete band of elevated uptake along the contralateral ventromedial border. 50 kHz stimulation evokes ventromedial banding in the contralateral, but not ipsilateral, ICC of undeprived 17-day-olds, though at a much reduced level relative to the adult. Following monaural conduction blockade from 12 to 17 days of age, stimulation through the reopened deprived ear elicits a band of uptake along the lateral ICC border, oblique to the normal tonotopic gradient. Cochlear mechanisms may account for modified patterning of high-frequency-evoked 2-DG uptake in ICC subsequent to conductive hearing loss during a period of elevated susceptibility to experiential factors.