Neurobehavioral effects of chronic ingestion of Great Lakes chinook salmon.

Cross-generational chronic feeding of either a 5 or a 20% lyophilized Lake Huron (LH) or Lake Ontario (LO) chinook salmon diet to rats caused no observable effects on many behavioral dimensions including activity, exploration, sensorimotor function, and stereotypy. As assessed by the Morris water maze and the radial arm maze, there was no diet-induced impairment of spatial learning or long-term memory. There was no evidence that the fish diets caused an exaggerated response to food reward reduction as had been observed previously for rats fed Oswego area Lake Ontario salmon. Effects of the fish diets with the exception of one statistically significant but probably meaningless effect on the Morris water maze for females were found only for male rats and only for males who ate the 20% diet. F1 male rats were reluctant to traverse a runway for a single pellet reward. Performance of the reference/working memory version of the radial arm maze was affected for the F1 LO-20 rats and for the F2 LH-20 rats. Until further research is conducted it would be unwise to ignore indications that male rats may show some effect of chronic consumption of the highest concentration of these diets, particularly on tasks that require intact frontocortical dopamine function.

Neurochemical, histopathological and mnemonic effects of combined lesions of the medial septal and serotonin afferents to the hippocampus.

Male Long-Evans rats received micro-injections of either N-methyl-D-aspartate (NMDA) in the medial septum/vertical diagonal band (MS/DB), 5,7-dihyroxytryptamine (5,7-DHT) in the fimbria/fornix and cingulate bundle or combined NMDA/5,7-DHT micro-injections. NMDA administration caused considerable damage to the MS and enlarged the lateral ventricles. It reduced the activity of choline acetyltransferase as well as the intensity of acetylcholinesterase staining in the hippocampus. 5,7-DHT selectively reduced the concentration of hippocampal serotonin. The rats were assessed for spatial memory in the Morris water maze and the radial arm maze (reference and working memory version). The 5,7-DHT-induced lesion of hippocampal serotonin had no effect by itself on either task. However, it augmented the reference memory impairment caused by the NMDA-induced lesion and delayed the recovery from NMDA-induced impairment of working memory on the radial maze. Combined damage of hippocampal cholinergic and serotonergic afferents did not severely affect spatial memory.

Neonatal brain dopamine depletion and the cortical and behavioral consequences of enriched postweaning environment.

This study investigated the effects of neonatal intraventricular administration of 6-hydroxydopamine (6-OHDA, 15 micrograms total with and without desmethylimipramine pretreatment) on the cortical thickening and behavioral effects of 35 days of enriched postweaning housing (ENR) in the rat. The 6-OHDA treatment depleted cortical dopamine (DA) to about 40% of control. It did not affect the thickness of the cerebral cortex nor did it affect the capacity for the cortex to be thickened by ENR. In addition, it did not alter the superior performance on two spatial water maze tasks that was caused by ENR. Thus, the potential for neurobehavioral plasticity was not changed by neonatal DA depletion. ENR eliminated the spatial learning/memory deficits that were caused by neonatal DA depletion and that were manifested when the rat was raised in standard (impoverished) laboratory conditions. Hence, environmental factors can modulate the cognitive effects of neonatal DA depletion. ENR did not attenuate the hyperactivity of the neonatal DA-depleted rat. This may reflect the subcortical mediation of this behavioral abnormality.