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Biomedical subjects

J N Armstrong

Publications and source records attributed to J N Armstrong.

6 recordsLinked to original sources
PubMed1992

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.

Animals↗
PubMed1991

The histopathological, behavioral and neurochemical effects of intraventricular injection of ethylcholine mustard aziridinium (AF64A) in the neonatal rat.

This study investigated the histopathological, behavioral and neurochemical effects of bilateral injection of 2.0, 0.5 and 0.1 nmol/ventricle ethylcholine aziridinium (AF64A) on postnatal day (PND) 2. The rats showed a significant, but non-dose-related reduction of choline acetyltransferase (ChAT) in the hippocampus but not the cerebral cortex or the caudate nucleus when sacrificed on PND 16. No effect on ChAT was found in any region at PND 58. The group given 2 nmol/ventricle were hyperactive and showed a deficit in spatial learning when tested on the Morris water maze at PND 38-43. No such differences were observed for the rats injected with 0.1 or 0.5 nmol/ventricle AF64A. This spatial learning impairment in the 2 nmol group was associated with non-specific tissue damage seen only in animals from this group that were sacrificed at PND 40. This tissue damage was most evident in the left medial frontal cortex, the caudate nuclei and the anterior dorsal hippocampus.

Animals↗
PubMed1990

Fatal embolism.

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Anesthesia↗
PubMed1990

Neonatal 6-hydroxydopamine alters the behavior of enriched-impoverished rats in a novel test environment.

The hypothesis that neonatal norepinephrine (NE) depletion lessens the behavioral consequences of differential housing was tested. Male Wistar rats were injected with 6-hydroxydopamine (6-OHDA) or vehicle twice within 24 hr of birth, weaned at 25 days, and reared under either impoverished (IC) or enriched conditions (EC) for 30 days. In 3 experiments, rats were tested in the Morris water maze, the colony-intruder test, and 2 tests of dominance. 6-OHDA treatment reduced cortical and hypothalamic NE concentrations and increased brainstem NE concentrations. EC housing increased cortical dopamine (DA). Behavioral differences caused by postweaning enrichment-isolation were reduced by neonatal NE depletion, primarily in early test trials. The authors conclude that forebrain NE afferents from the locus coeruleus are important for housing-related behavioral changes and responsivity to novel testing environments.

Agonistic Behavior↗
PubMedDate not supplied

Enriched housing masks deficits in place navigation induced by neonatal monosodium glutamate.

Monosodium-L-glutamate (MSG)-induced behavioural deficits were examined under two housing conditions. Male Wistar rat pups were cross-fostered at birth and injected with MSG on days 2 to 11 postpartum. Control pups were injected with saline (Sal) of equivalent volume. Following weaning at day 25 the rats were allocated to either "enriched" (EC) or "impoverished" (IC) housing, thus forming four treatment groups: MSG-EC, MSG-IC, Sal-EC, and Sal-IC. Thirty-five days later all rats were tested in the open field and in the place navigation task. Multivariate analysis of variance (MANOVA) revealed a significant two-way interaction of the housing x drug variables. While the MSG-IC rats were deficient in the water maze, the performance of the MSG-EC approached that of saline-injected controls. Although the Sal-IC rats developed higher body weights than the Sal-EC rats the MSG-EC and MSG-IC rats did not differ in body weight. The housing by drug treatment interaction was not apparent in the open field.

Adrenal Glands↗