Effects of prolonged retinal ganglion cell inactivity on superior colliculus glucose metabolism in the mature hooded rat.
Previous work utilizing the 2-deoxyglucose (2-DG) technique demonstrated that denervation, both direct (enucleation) or indirect (retinal receptor destruction, leaving ganglion cells intact), resulted in a depression followed by an increase in glucose metabolism in the superior colliculus (SC) of the mature hooded rat. Both enucleation and receptor loss result in (1) cessation of ganglion cell activity and (2) disruption of connections between visual system neurons. To examine the relative importance of these two factors to the metabolic depression-"recovery" sequence, retinal ganglion cells were silenced without denervation for periods ranging from 24 h to 2 months by means of repeated intraocular tetrodotoxin (TTX) injections. SC metabolic activity fell to levels comparable to those seen after enucleation or receptor damage, but no recovery was detected. A more sensitive within-animal comparison was carried out to detect any small shifts in metabolic activity which might have occurred during retinal blockade; after 1 or 2 months of monocular TTX treatment, either binocular enucleation or binocular TTX injections were performed 24 h before 2-DG, depriving both sides of the SC of retinal input. Metabolic activity was slightly higher in the SC that had received no retinal input for 1 or 2 months, indicating that physiological changes had occurred within the SC during the afferent blockade. A second group of rats was allowed to recover from the effects of long-term TTX for from 1 to 12 days and binocularly exposed to visual stimuli during 2-DG uptake to determine whether damage had resulted from the TTX injections and to assess the time course of the effects of retinal blockade on SC functional activity.(ABSTRACT TRUNCATED AT 250 WORDS)
Thurlow
G A
GA
Psychology Department, University of Calgary, Alberta, Canada.
Cooper
R M
RM
D000375:Aging / Q000378:metabolism*; D000818:Animals; D001345:Autoradiography; D003847:Deoxyglucose / Q000378:metabolism; D005947:Glucose / Q000378:metabolism; D008297:Male; D051381:Rats; D011919:Rats, Inbred Strains; D012160:Retina / Q000502:physiology*; D012165:Retinal Ganglion Cells / Q000502:physiology*; D013477:Superior Colliculi / Q000378:metabolism*; D013779:Tetrodotoxin / Q000494:pharmacology; D013997:Time Factors
D013779:Tetrodotoxin; D003847:Deoxyglucose; D005947:Glucose