Quantitative studies of the effects of aging, meclofenoxate, and dihydroergotoxine on intraneuronal lipopigment accumulation in the rat

Stroke-Induced Neurogenesis in Aged Brain

Background and Purpose— Stroke induced by middle cerebral artery occlusion (MCAO) triggers increased neurogenesis in the damaged striatum and nondamaged hippocampus of young adult rodents. We explored whether stroke influences neurogenesis similarly in the aged brain.

Methods— Young adult (3 months) and old (15 months) rats were subjected to 1 hour of MCAO, and new cells were labeled by intraperitoneal injection of 5-bromo-2′-deoxyuridine 5′-monophosphate (BrdU), a marker for dividing cells, for 2 weeks thereafter. Animals were euthanized at 7 weeks after the insult, and neurogenesis was assessed immunocytochemically with antibodies against BrdU and neuronal markers with epifluorescence or confocal microscopy.

Results— Young and old rats exhibited the same increased numbers of new striatal neurons after stroke, despite basal cell proliferation in the subventricular zone being reduced in the aged brain. In contrast, both the number of stroke-generated granule cells and basal neurogenesis in the dentate subgranular zone were lower in old compared with young animals. Also, the ability of newly formed cells to differentiate into neurons was impaired in the aged dentate gyrus.

Conclusions— Basal neurogenesis is impaired in the subgranular and subventricular zones of aged animals, but both regions react to stroke with increased formation of new neurons. The magnitude of striatal neurogenesis after stroke is similar in young and old animals, indicating that this potential mechanism for self-repair also operates in the aged brain.

Age-related decline in multiple unit action potentials of CA3 region of rat hippocampus: correlation with lipid peroxidation and lipofuscin concentration and the effect of centrophenoxine

Changes in lipid peroxidation, lipofuscin concentration, and multiple unit activity (MUA recorded in conscious animals) in the CA3 region were studied in the hippocampus of male Wistar rats aged 4, 8, 16, and 24 months. The lipid peroxidation and lipofuscin concentration were increased with age. The MUA, however, declined with age. Correlational analyses were performed for the four age groups to determine the relationship between the age-associated decline in MUA with the age-related alterations in lipid peroxidation and lipofuscin concentrations. The age-related increase in lipid peroxidation correlated positively with the age-associated increase in lipofuscin concentration. The age-related increases in lipid peroxidation and lipofuscin concentration correlated negatively with the changes in MUA. Since lipid peroxidation may affect neuronal electrophysiology, our data suggested that age-related increase in lipid peroxidation may contribute to an age-associated decline in neuronal electrical activity. Centrophenoxine effects were studied on the three above-mentioned age-associated changes in the hippocampus. The drug had no effect on all three parameters in 4- and 8-month-old rats. In 16- and 24-month-old rats, however, the drug significantly increased the MUA but concomitantly decreased lipofuscin concentration and lipid peroxidation. Correlational analyses of the data on MUA, lipid peroxidation and lipofuscin concentration from the centrophenoxine-treated animals showed that the drug-induced diminution in both lipofuscin and lipid peroxidation was significantly correlated with the drug-induced increase in MUA. The differential effect of the drug in younger (4-8 months) and older (16-24 months) animals indicated that the stimulation of MUA was clearly associated with concomitant decrease in lipid peroxidation and lipofuscin concentration.

The effects of ageing and a vitamin E-deficient diet on the lipopigment content of rat hippocampal and Purkinje neurones

This study examined associations between a vitamin E-deficient diet, ageing and aspects of the morphology of neuronal lipopigment in rat hippocampal and Purkinje neurones. Groups of rats given a standard diet were killed at 6, 12, 18 and 25 months of age, while a group which had received a vitamin E-deficient diet from 1-18 months were killed at 18 months of age. Lipopigment within a neuronal cell body consists of a number of discrete regions of varying size. These were identified by fluorescence microscopy and a photograph for each individual neurone was projected onto paper, so that the outlines of the discrete regions of lipopigment could be drawn and subjected to morphometric measurements. Both ageing and vitamin E deficiency in relation to hippocampal neurones and vitamin E deficiency in relation to Purkinje neurones (in which ageing effects were not examined), were associated with a significant (< 0.05) increase in the mean total area (per rat) enclosed by the lipopigment outlines. For both vitamin E deficiency and ageing this increase was associated with both an increase in the number of relatively large discrete lipopigment regions and a decrease in the number of relatively small discrete lipopigment regions. The findings in relation to vitamin E deficiency could be explained by an increased rate of lipopigment formation, involving processes which also occur in ageing.

Lipopigment in rat hippocampal and Purkinje neurones after chronic phenytoin administration

The accumulation of lipopigment may indicate ageing, certain diseases and cellular damage, while phenytoin, which has been claimed to cause selective clinical cerebellar dysfunction and degeneration, has been reported to produce increased lipopigment accumulation in rat Purkinje neurones. In the present study, 8 rats received phenytoin, 300 mg/kg/day for 20 weeks, and were compared with a control group of 9 rats in respect of lipopigment in Purkinje and hippocampal neurones. Neuronal lipopigment was identified by fluorescence microscopy. The results did not indicate that phenytoin administration was associated with an increase in the area corresponding to (i.e. within the outlines of) neuronal lipopigment in Purkinje neurones, although the relatively small number of animals limits the power of the study. However, in hippocampal neurones, a two-way analysis of variance for numbers of discrete regions of lipopigment demonstrated a significant interaction (P = 0.003) between, firstly, size categories of discrete regions of lipopigment and, secondly, phenytoin administration or a control procedure. In hippocampal neurones, phenytoin administration was accompanied by a decrease in the numbers of discrete lipopigment regions in the smaller size categories and an increase in the numbers in the larger size categories. This finding indicates the need for further investigation into the effects of phenytoin on brain regions other than the cerebellum, as intellectual deterioration may be related to chronic use of this drug.

Reduced lipofuscin accumulation in senescent rat brain by long-term acetyl-L-carnitine treatment

By using fluorescence microscopy and microfluorimetric techniques, the effects of ageing and of 11 months acetyl-L-carnitine (ALCAR) treatment on lipofuscin deposition within the cytoplasm of pyramidal neurons of rat prefrontal cortex and hippocampus (CA3 field) were assessed. No lipofuscin autofluorescence was observed in the nerve cell bodies of neurons under study in young rats (3 months of age), but lipopigment had accumulated in the same nerve cells of senescent rats (22 months of age). ALCAR administration significantly reduced the accumulation of lipofuscin within pyramidal neurons of the brain areas examined.

Effects of centrophenoxine on cholinephosphotransferase activity in maternal and fetal guinea pig lung

Cholinephosphotransferase activities of guinea pig lung mitochondria and microsomes are inhibited by centrophenoxine and one of its metabolites, p-chlorophenoxyacetate. 2-Dimethylaminoethanol, the second metabolite of centrophenoxine, has no inhibitory effect on the enzyme activity. The inhibition of enzyme activity by centrophenoxine is noncompetitive. Intravenous injection of centrophenoxine and p-chlorophenoxyacetate to pregnant animals causes inhibition of cholinephosphotransferase activity in adult lung but not in fetal lung. However, direct administration of centrophenoxine to the fetus after laparotomy causes inhibition of both subcellular enzyme activity in fetal lung. It is suggested that the drug injected to the pregnant animals does not reach the fetal lung or is metabolized. Furthermore, while centrophenoxine injection does not change the total phosphatidylcholine content of adult lung, the acyl group composition of phosphatidylcholine was modulated.

Neuronal lipopigment: a marker for cognitive impairment and long-term effects of psychotropic drugs

Lipopigment, identifiable in the fluorescence microscope, is thought to be cellular debris partly derived from free-radical-induced peroxidation of cellular constituents. The volume of neuronal lipopigment has been positively correlated with advancing age, Alzheimer dementia, and the neuronal ceroidoses, while various changes in neuronal lipopigment have been reported in association with the chronic administration of dihydroergotoxine, ethanol, phenytoin, centrophenoxine, and chlorpromazine. An increase in the volume of neuronal lipopigment may indicate increased functional activity of the cell, impaired removal of pigment or anoxia. Chronic administration of agents which can be correlated with decreased neuronal lipopigment in animal models might protect neuronal function against any adverse effects associated with (but not necessarily resulting from) lipopigment accumulation in normal ageing, anoxia, or certain degenerative diseases. Long-term studies of the prophylactic use of such agents, or of drugs which neutralise free radicals, may be indicated. Other clinical applications of such drugs may include protection against the effects of free radicals formed during periods of oxygen deprivation.

Redistribution of lipofuscin in aged neurons induced by colchicine

The effect of a single, 40 micrograms, intracerebroventricular injection of colchicine on the distribution of neuronal lysosomes and lipofuscin granules in aged mice was studied. At the light microscope level we observed that colchicine induced a redistribution of dipeptidyl aminopeptidase II (Dpp II), a lysosomal and lipofuscin granule marker enzyme, from the cell bodies of neurons to the dendrites; cell bodies became depleted of Dpp II while dendrites became enriched with this enzyme. Quantitation of this phenomenon at the electron microscope level demonstrated that colchicine induced a rapid and significant decrease in the density of lysosomes and lipofuscin granules from the somata of neurons whereas in dendrites we observed a significant increase in the density of these organelles.