Neonatal 6-OHDA lesions and rearing in complex environments: regional effects on adult brain 14C-2-deoxyglucose uptake revealed by exposure to novel stimulation.
Behavioral and neuromorphological data have suggested at least a partial interaction between the effects of norepinephrine-depleting neonatal 6-OHDA lesions and the effects of rearing in enriched environments. The present study examined the impact of both of these early manipulations upon regional brain uptake of 14C-2-deoxyglucose (14C-2DG) in adulthood. Newborn rats received 6-OHDA (50 mg/kg s.c.) or vehicle and, after weaning at 25 days, were reared in isolated versus enriched conditions. Regional brain 14C-2DG uptake was then examined at 70-80 days of age--either in the home cage or while animals were being exposed to novel, presumably arousing, stimulation. Ninety-seven brain regions were examined in eight separate groups. Results indicated that (1) Under baseline conditions, neither neonatal 6-OHDA nor differential rearing conditions produced widespread alterations in regional brain 14C-2DG uptake profiles. An overall enrichment effect was seen on only five brain areas, with rats reared in enriched environments showing lower levels of 14C-2DG uptake (-20% to -30%) than isolated rats. Neonatal 6-OHDA produced no main effect on 14C-2DG uptake in any brain region. (2) In contrast, when 14C-2DG uptake was assessed during exposure to a novel environment, five brain areas showed differential 14C-2DG uptake in 6-OHDA-treated rats, and 20 brain areas showed differential uptake in rats reared in enriched conditions. (3) No significant interaction effect on brain regional 14C-2DG uptake was observed between neonatal 6-OHDA and environmental complexity factors. These results are consistent with the notion that enduring effects of rearing and early 6-OHDA treatment may, independently, relate to a general reactivity factor. They also indicate that some effects of early neurochemical injury and subsequent experiential factors may not be apparent under normal resting conditions, but only become evident in the presence of appropriate "activating" stimulation.
Nobrega
J N
JN
Neuroimaging Research Section, Clarke Institute of Psychiatry, Toronto, Ontario, Canada.
Saari
M J
MJ
Armstrong
J N
JN
Reed
T
T
D000818:Animals; D000830:Animals, Laboratory; D000831:Animals, Newborn; D001835:Body Weight; D001921:Brain / Q000378:metabolism*; D046508:Culture Techniques; D003847:Deoxyglucose / Q000097:blood / Q000378:metabolism / Q000493:pharmacokinetics*; D004777:Environment; D005260:Female; D006801:Humans; D007231:Infant, Newborn; D008297:Male; D009473:Neuronal Plasticity / Q000502:physiology; D009638:Norepinephrine / Q000378:metabolism / Q000493:pharmacokinetics*; D016627:Oxidopamine / Q000378:metabolism / Q000493:pharmacokinetics*; D051381:Rats; D011919:Rats, Inbred Strains
D016627:Oxidopamine; D003847:Deoxyglucose; D009638:Norepinephrine