Resting and pure tone evoked metabolic responses in the inferior colliculus of young adult and senescent rats.
Metabolic responses from three sectors of the inferior colliculus (IC) divided according to frequency representation were examined bilaterally in young (YA) and aged adult (AA) rats using the 2-deoxyglucose method under quiescent or pure tone stimulus conditions. Resting IC metabolism in YA rats is characterized by elevated glucose uptake in the ventromedial (high frequency) relative to intermediate and dorsolateral sectors. AA resting incorporation is not reduced in any sector and is more uniform than YA uptake. Monaural high frequency stimulation (50 kHz) in YA animals evokes discrete contralateral banding along the ventromedial IC border, while stimulation in the optimal auditory sensitivity range of the rat at 8 kHz activates the intermediate sector of the contralateral IC. Although 50 kHz evoked ventromedial uptake is slightly reduced in AA rats contralaterally, the overall uptake within the three sectors does not differ significantly between ages under either of the monaural stimulus conditions; therefore senescent stability is exhibited. However, in AA rats the focus to 8 kHz stimulation has less clearly defined borders even though uptake within the intermediate sector is undiminished compared to YA animals, while 50 kHz elicited activity is typically reduced to a discontinuous band in the ventromedial sector of AA animals. These senescent changes may represent compensation in IC metabolism to changes in cochlear processing which are reflected in the activity of ascending auditory pathways.
D000161:Acoustic Stimulation; D000375:Aging; D000818:Animals; D003837:Deoxy Sugars / Q000378:metabolism*; D003847:Deoxyglucose / Q000378:metabolism*; D004431:Ear, External / Q000254:growth & development / Q000502:physiology; D004432:Ear, Middle / Q000254:growth & development / Q000502:physiology; D007245:Inferior Colliculi / Q000254:growth & development* / Q000378:metabolism; D051381:Rats; D011919:Rats, Inbred Strains; D014316:Tritium
D003837:Deoxy Sugars; D014316:Tritium; D003847:Deoxyglucose