DSP-4, a noradrenergic neurotoxin, produces more severe biochemical and functional deficits in aged than young rats

The present study examines the effects of noradrenergic lesions (either DSP-4 i.p. or 6-hydroxydopamine (6-OHDA) into the dorsal noradrenergic bundle on biochemical (noradrenaline (NA), dopamine (DA), serotonin (5-HT) and choline acetyltransferase (ChAT) activity) and cortical EEG (quantitative EEG (qEEG) and high-voltage spindle (HVS) activity in young and aged rats. Near complete 6-OHDA NA lesions, but not partial DSP-4 NA lesions, increased HVS activity in young rats. DSP-4 and 6-OHDA lesions produced no significant changes in the 5-HT or DA levels or in the ChAT activity in young rats. In some of the aged rats, DSP-4 produced similar biochemical and HVS effects, as it induced in young rats. In the remainder of the aged rats, NA levels were greatly and 5-HT levels slightly decreased. DA levels and ChAT activity were unaltered in either set of aged rats. HVS activity was increased only in that group of aged rats with the greatly lowered NA content. These results suggest that: (1) some of the aged rats are more sensitive to DSP-4 treatment than young adult rats; and (2) NA depletions have to be complete to produce an increase in HVS activity in young and aged rats.     

Choline acetyltransferase activity in murine thymus.

Murine thymus has been demonstrated to contain both cholinergic receptors and acetylcholinesterase activity. In the present study we have investigated the presence of the enzyme choline acetyltransferase in this organ, which is responsible for the synthesis of acetylcholine. Results reported here demonstrate that (1) an appreciable amount of the enzyme is already present in the thymus on the day of birth; (2) its expression is developmentally regulated; and (3) thymic atrophy, induced in young (2-week-old) and adult (6-week-old) mice by i.p. injection of hydrocortisone for 2 days, is accompanied by significant reduction of choline acetyltransferase activity only in young mice. Altogether these results demonstrate the presence in the murine thymus of functionally relevant markers of the cholinergic system that might interface the interactions between the nervous and immune systems.     

C-fos expression in the rat nucleus basalis upon excitotoxic lesion with quisqualic acid: a study in adult and aged animals

Summary. A unilateral quisqualic acid lesion was placed in the nucleus basalis magnocellularis of 3- and 24-month-old rats, and the animals were sacrificed at different times post-surgery. The morphology and the number of the cholinergic neurons of the nucleus basalis were analyzed by means of immunohistochemistry for cholineacetyltransferase, in order to evaluate the size and severity of the lesion. Immunohistochemistry for the immediate early gene c-fos was also performed in order to clarify its role in the process of neurodegeneration following the excitotoxin injection. The DNA laddering and TUNEL techniques were used to define the type of cell death involved. At short times (4 hr) the lesion induced alterations in the morphology of cholinergic neurons of the nucleus basalis. Subsequently, a significant decrease in the number of neurons was found in comparison to the contralateral unlesioned side. In the older animals the loss of cholineacetyltransferase immunoreactivity had an earlier onset (4 hr) than in the young (24 hr). C-fos expression was induced by the lesion and not by saline injection in the nucleus basalis and in neighbouring areas of the brain as early as 4 hr after surgery. The c-fos protein was no longer present by 24 hr. Furthermore, the c-fos gene product was consistently absent from the nuclei of cholinergic cells. The aged animals exhibited a slower and smaller increase in c-fos as measured by counting the labelled nuclei in the injected area. Analysis of DNA fragmentation did not provide any evidence for apoptosis as the type of cell death involved in the cholinergic degeneration. These results indicate that the c-fos protein might have a protective role in the response to excitotoxic lesions. Furthermore, we have shown that the aged brain displays a reduced ability to produce a c-fos-mediated plastic response to the lesion. Received December 17, 1997; accepted February 17, 1998     

The stimulating effect of ganglioside injections on the recovery of choline acetyltransferase and acetylcholinesterase activities in the hippocampus of the rat after septal lesions

The effect of intramuscular administration of a mixture of gangliosides (21% GM₁, 39.7% GD_1a,, 16% GD_1b, 19% GT₁ in a daily dose of 50 mg per kg upon the time course of changes in hippocampal acetylcholinesterase and choline acetyltransferase activities after extensive medioventral septal lesions in the rat was checked on days 3, 5, 18 and 50 after the operation. Following the early decrease in the enzyme activities to about 25% of control due to degeneration, a gradual recovery up to about 50% of control activity at the 50th day was found. When gangliosides were administered, the recovery in the activity of both enzymes was more pronounced. The ratio of the enzyme activities from the animals injected with gangliosides to that from uninjected animals was 1.45 and 1.48 on the 18th day and 1.62 and 1.50 on the 50th day after the operation, for choline acetyltransferase and acetylcholinesterase activity, respectively. Since no significant effect of ganglioside injection was seen at early postoperative times i.e. on days 3 and 5, the effects seen on days 18 and 50 seem to be specifically due to facilitation of the recovery processes and not to retardation of the degeneration processes.Assuming that the spontaneous recovery of cholinergic enzyme activity reflects reinnervation of the hippocampus through collateral sprouting, gangliosides would seem to facilitate the regrowth of new cholinergic nerve terminals.     

The isolation of pure cholinergic nerve terminal sacs (T-sacs) from the electric organ of juvenile Torpedo.

The problem of synaptosome formation in the electric organ of Torpedo has been re-investigated using tissue from juvenile fish. This tissue is softer than adult material and can be easily homogenized in an Aldridge-type homogenizer. Homogenates so prepared contain a significant number of synaptosome-like structures which can be purified by differential and density gradient centrifugation. The purified particles are enriched in acetylcholine and choline acetyltransferase; they also contain lactate dehydrogenase activity, most of which is in an occluded form. The structure of these particles as revealed by electron microscopy is unusual in that they have no post-synaptic adhesions, relatively few synaptic vesicles and no intraterminal mitochondria. Because of their unusual morphology we have named these particles nerve terminal sacs (T-sacs). A high-affinity, hemicholinium-3 sensitive choline uptake system with an apparent K_m of 1–3 μm is associated with the T-sacs.     

Central cholinergic pathways in the rat: An overview based on an alternative nomenclature (Ch1–Ch6)

Monoclonal antibodies to choline acetyltransferase and a histochemical method for the concurrent demonstration of acetylcholinesterase and horseradish peroxidase were used to investigate the organization of ascending cholinergic pathways in the central nervous system of the rat. The cortical mantle, the amygdaloid complex, the hippocampal formation, the olfactory bulb and the thalamic nuclei receive their cholinergic innervation principally, from cholinergic projection neurons of the basal forebrain and upper brainstem. On the basis of connectivity patterns, we subdivided these cholinergic neurons into six major sectors. The Chl and Ch2 sectors are contained within the medial septal nucleus and the vertical limb nucleus of the diagonal band, respectively. They provide the major cholinergic projections of the hippocampus. The Ch3 sector is contained mostly within the lateral portion of the horizontal limb nucleus of the diagonal band and provides the major cholinergic innervation to the olfactory bulb. The Ch4 sector includes cholinergic neurons in the nucleus basalis, and also within parts of the diagonal band nuclei. Neurons of the Ch4 sector provide the major cholinergic innervation of the cortical mantle and the amygdala. The Ch5–Ch6 sectors are contained mostly within the pedunculopontine nucleus of the pontomesencephalic reticular formation (Ch5) and within the laterodorsal tegmental gray of the periventricular area (Ch6). These sectors provide the major cholinergic innervation of the thalamus. The Ch5–Ch6 neurons also provide a minor component of the corticopetal cholinergic innervation.

These central cholinergic pathways have been implicated in a variety of behaviors and especially in memory function. It appears that the age-related changes of memory function as well as some of the behavioral disturbances seen in the dementia of Alzheimer's Disease may be related to pathological alterations along central cholinergic pathways.     

Guidance of acetylcholinesterase-containing fibres by target tissue in co-cultured brain slices

Slices of various brain regions were prepared from newborn and from 7-day old rats and co-cultured in different combinations. In the majority of co-cultures of septal and hippocampal slices, acetylcholinesterase-positive fibres originating in the septal nuclei invaded the adjacent hippocampal slice. A similar pattern of hippocampal ingrowth by acetylcholinesterase-positive fibres occurred with slices prepared from the nucleus basalis of Meynert and from spinal cord. Septal neurones also projected to cortical slices, an effect which even occurred in the presence of their natural target tissue. In contrast to these massive projections to brain areas which in situ receive cholinergic inputs, no significant acetylcholinesterase-positive fibre ingrowth was observed in tissues which lack major cholinergic afferents in situ (hypothalamus, substantia nigra and cerebellum). These results indicate that under our culture conditions, acetylcholinesterase-positive fibres selectively invade cholinergic target areas. This effect is independent of the brain area from which the cholinergic neurones were derived.     

Relaxation times of choline, creatine and N-acetyl aspartate in human cerebral white matter at 1.5 T

Several studies have investigated the T1 and T2 relaxation time of choline, creatine and N-acetyl aspartate in cerebral white matter in normal human subjects. However, these studies demonstrate a large variation in T1 and T2 values. In the present study, relaxation times of choline, creatine and N-acetyl aspartate were determined in cerebral white matter in 15 control subjects (age 21 +/- 2 y, mean +/- SD) at 1.5 T. Using PRESS, seven or eight data points were obtained to fit the T1 and T2 relaxation curves to, respectively. The mean voxel size was 14 cm3. The T1 relaxation times of choline, creatine and N-acetyl aspartate were 1091 +/- 132 (mean +/- SD), 1363 +/- 137 and 1276 +/- 132 ms. The T2 relaxation times were 352 +/- 52, 219 +/- 29 and 336 +/- 46 ms, respectively.     

Trimethylaminuria in a girl with Prader-Willi syndrome and del(15)(q11q13)

We report on an individual with trimethyl-aminuria, Prader-Willi syndrome, and del(15) (q11q13). To our knowledge, such an association has never been reported. Skin sores secondary to choline-rich foods and amenable to dietary control have not been described in trimethylaminuria, although they are seen in some patients with Prader-Willi syndrome. Pathogenesis, clinical diagnosis, and management of reported cases with trimethylaminuria are reviewed. Serious social and behavioral problems may result from strong body odor. Amelioration of the “fish odor” by dietary choline restriction makes trimethylaminuria detection important. Association of trimethylaminuria with Prader-Willi syndrome and del(15) (q11q13) in this patient is of particular interest. It may represent a contiguous gene syndrome, or deletion of the normal allele leading to expression of a single recessive trimethylaminuria gene, or an unrelated association, such as in Noonan syndrome. However, recent development of mapping of flavin-containing monooxygenase 2 (FMO2), the likely enzyme that is defective in fish odor syndrome, to chromosome 1q probably excludes pathogenetic association of fish odor syndrome with the Prader-Willi syndrome. © 1993 Wiley-Liss, Inc.