Delayed and blunted induction of mRNA for tissue plasminogen activator in the brain of old rats following pentylenetetrazole-induced seizure activity

The ability of the rodent brain to support plasticity-related phenomena declines with increasing age. Here we investigated the extent to which old rats retain the capacity to initiate transcription for immediate early genes, particularly as it relates to brain plasticity, in response to a strong stimulus. The intraperitoneal administration of pentylenetetrazole (PTZ) to rats of various ages evoked tonic-clonic seizures. Using an RNA gel-blot and in situ hybridization analysis, we found that 1 hour after the onset of seizure, messenger RNA (mRNA) for tissue plasminogen activator (TPA) was increased approximately 3.7-fold in the hippocampi of 3-month-old rats. The levels of TPA mRNA in the hippocampi and cortices of 3-month-old rats returned to control levels by 3 hours after PTZ administration. The levels of TPA mRNA increased 2.5-fold in the hippocampi of 18-month-old rats and 1.8-fold in the brains of the 28-month-old-rats at 3 hours and returned to basal levels by 15 hours following PTZ treatment. Quantitatively similar increases were calculated for the cortex. At peak induction the transcripts were localized throughout the cortical layers of the 3-month-old rats, whereas the TPA mRNA expression was restricted to cortical layer V of the older rats. Our results suggest that although the aging brain retains the capacity to respond to chemically induced seizures, the induction of TPA mRNA is temporarily delayed and the levels are diminished with increasing age. Because TPA has been implicated in neuronal plasticity, this finding suggests that immediate early genes are important factors in the limited plasticity of the aging brain.

Effect of borage oil consumption on fatty acid metabolism, transepidermal water loss and skin parameters in elderly people

Human skin is not able to biosynthesize gamma-linolenic acid (GLA, 18:3omega6) from the precursor linoleic acid (LA), or arachidonic acid (AA) from dihomo-gamma-linolenic acid (DHGLA). Dietary supplementation with GLA-rich seed oil of borage skips the step of hepatic 6-desaturation of fatty acids (FA) and, therefore, compensates the lack of these essential FA in conditions with impaired activity of delta 6-desaturase. Twenty-nine healthy elderly people (mean age 68.6 years), received a daily dose of 360 or 720 mg GLA for 2 months, using Borage oil in gelatine capsules (Quintesal 180, manufacturer Galderma Laboratorium GmbH, Freiburg, Germany). The effects of fatty acids derived from ingested borage oil capsules on skin barrier function were assessed by measurement of transepidermal water loss (TEWL). The consumption of borage oil induced a statistically significant improvement of cutaneous barrier function in the elderly people, as reflected in a mean decrease of 10.8% in the transepidermal water loss. Thirty-four percent of the people noted itch before borage oil consumption and 0% afterwards. Dry skin was claimed to be reduced from 42 to 14%, but no significant alteration of skin hydration was measured. The FA-composition of erythrocyte membrane phospholipids demonstrated an increase of GLA (+70%) and DHGLA (+18%) and a reduction of saturated and monounsaturated FA. There was no significant alteration in nervonic acid or in AA content, but an increase in the DHGLA/AA ratio (+23%). Thus, the consumption of borage oil by elderly people lead to alteration of FA metabolism and improved skin function.

Proton translocating ATPase mediated fungicidal activity of a novel complex carbohydrate: CAN-296

CAN-296 is a complex carbohydrate (approximately 4300 Da) isolated from the cell wall of Mucor rouxii. It exhibits excellent in vitro fungicidal activity against a wide spectrum of pathogenic yeasts, including isolates resistant to azoles and polyenes. The rapid irreversible action of CAN-296 on intact fungal cells and protoplasts suggested a membrane-located target for its action. The proton translocating ATPase (H+-ATPase) of fungi is an essential enzyme required for the regulation of intracellular pH and nutrient transport. Inhibition of H+-ATPase leads to intracellular acidification and cell death. We therefore investigated the effect of CAN-296 on H+-ATPase-mediated proton pumping by intact cells of Candida and Saccharomyces species by measuring the glucose-induced acidification of external medium. CAN-296 inhibited proton pumping of Candida albicans, Candida glabrata, Candida krusei, Candida guilliermondii and Saccharomyces cerevisiae at low concentrations (0.078-1.25 mg/l). Other commonly used antifungal agents such as amphotericin B, itraconazole and fluconazole had no effect on H+-ATPase-mediated proton pumping. A clinical isolate of C. glabrata with reduced in vitro susceptibility (MIC = 10 mg/l) to CAN-296 also showed resistance to CAN-296 inhibition of proton pumping. Purified membrane fractions rich in H+-ATPase activity were not inhibited by CAN-296 suggesting that the effect on the H+-ATPase-mediated proton pumping in intact yeast cells is an indirect effect, perhaps mediated by local or global disruption of the plasma membrane. These results suggest that the inhibition of fungal H+-ATPase is at least partly responsible for the antifungal activity of CAN-296.

Anomalous expression of microtubule-associated protein 1B in the hippocampus and cortex of aged rats treated with pentylenetetrazole

The aim of the present study was to assess the age-dependent response of microtubule-associated protein 1B, a plasticity-associated protein deriving from a late gene, following administration of an epileptogenic stimulus. The effect of a single administration of the convulsant pentylenetetrazole on microtubule-associated protein 1B expression in the hippocampal formation and cortex of three-, 18- and 28-month-old rats was assessed using northern blot analysis, in situ hybridization and immunohistochemistry. In three-month-old rats, we detected initial increases in microtubule-associated protein 1B messenger RNA at 15 h following pentylenetetrazole administration in the granule cells of the dentate gyrus, in the CA3 region of the hippocampus and in layers II/III of the entorhinal cortex, and these reached a maximum at 44 h. However, in the hippocampus and cortex of 18-month-old rats, the peak occurred at 15 h, and in the brains of 28-month-old rats a blunted peak was reached at 3 h. Pentylenetetrazole treatment in young rats resulted in a robust induction of microtubule-associated protein 1B immunoreactivity in the granule cells of the dentate gyrus and in layers II/III of the entorhinal cortex, but also produced a large decrease in the retrosplenial cortex. However, following pentylenetetrazole treatment in older rats, the granule cells of the dentate gyrus were nearly devoid of microtubule-associated protein 1B immunoreactivity, whereas the retrosplenial cortex showed no changes at all, and the entorhinal cortex had an expression pattern similar to that of young rats. Aberrant immunolabeling of microtubule-associated protein 1B occurred in cortical layer VI of the aged rats where, unlike in young rats, there was heavy staining of neuronal somata. These results suggest that the regulation of the plasticity-associated protein microtubule-associated protein 1B is altered in the ageing rat brain, with the peak of expression shifted to earlier times in 18-month-old rats and blunted, variable increases at even earlier times in 28-month-old rats.

Age-dependent changes of the kidneys: pharmacological implications

About 40% of the intoxications after drug administration occur in the elderly. A significant proportion of the disease states in elderly patients is related to adverse reactions to prescribed drugs. Declining renal function, a reduction in both renal blood flow and glomerular filtration rate, is a major contributor to drug toxicity in the elderly. Therefore, a review (based on newer papers from Medline) of age-dependent changes of the kidneys and their consequences for drug therapy in geriatric patients is presented. Renal changes that occur with aging are: a decrease of renal weight, a thickening of the intrarenal vascular intima, sclerogenous changes of the glomeruli, and infiltration of chronic inflammatory cells and fibrosis in the stroma. Altered renal tubular function, including impaired handling of water, sodium, acid, and glucose, is also frequently present in old age. Impaired 'endocrinologic' functioning manifested by changes of the renin-angiotensin system, vitamin D metabolism, and antidiuretic hormone responsiveness has been reported. The aging kidney is constantly exposed to the effects of a variety of potential toxic processes, i.e., drugs and chronic illnesses including hypertension, diabetes, and atherosclerotic disease. Renal changes that occur with aging also consist of impairment in the ability to concentrate urine and to conserve sodium and water. These physiological changes increase the risks of volume depletion and prerenal type of acute renal failure. A frequent cause of acute renal failure in the elderly is drug-induced nephropathy. Nonsteroidal anti-inflammatory drugs, antibiotics, and diuretics are most often involved. Due to the age-dependent decline of renal function, the pharmacokinetics of many drugs are altered in elderly patients. Therefore, the most important renal function to monitor with aging is the creatinine clearance. Changes in pharmacokinetics of many drugs and most decisions on drug dosage can be based on this information alone, as tubular functions of the kidney decrease at rates paralleling the age-dependent decrease in glomerular filtration rate (which is approximately measured by the creatinine clearance). As a conclusion, age-dependent changes of renal function are not only responsible for changes in pharmacokinetics and pharmacodynamics. In many cases, the kidneys are the target organ of adverse drug reactions too.

Involvement of calcium inhibitable binding to the cell wall in the fungicidal activity of CAN-296

CAN-296 is a heat stable, complex carbohydrate (molecular mass 4300 Da) isolated from the cell wall of the filamentous fungus Mucor rouxii. It possesses potent in-vitro fungicidal activity against a wide spectrum of pathogenic yeasts, including azole-resistant isolates of Candida albicans and Candida glabrata. As a preliminary step in the study of the mode of action of this novel antifungal agent, we investigated the effect of various cations on the antifungal activity as well as the binding of CAN-296 to intact cells and cell-wall fractions of C. albicans. The antifungal activity of CAN-296 was inhibited by low concentrations of calcium, magnesium and lithium and by high concentrations of barium, cobalt and manganese, but not by potassium and copper. The calcium-mediated inhibition of the antifungal activity of CAN-296 was readily reversible by the removal of calcium by dialysis, and the fungicidal activity of the inhibited compound was fully restored. The uptake/binding of CAN-296 to intact cells and to the cell-wall fraction of C. albicans was time and concentration dependent. Maximum uptake/binding was obtained at 5 mg/L within 60 min and was associated with the aggregation of intact cells. Washing intact cells and the cell-wall fraction preincubated with radiolabelled CAN-296 with 150-fold excess of unlabelled compound failed to remove CAN-296 associated with the intact cells and the cell-wall fraction, suggesting that the binding of CAN-296 to C. albicans is tight. The uptake/binding of CAN-296 and the drug-mediated aggregation of intact cells were inhibited by calcium in a concentration-dependent manner. The fact that CAN-296 is a fungicidal agent that binds to intact cells and the cell-wall fraction of C. albicans very tightly, together with the observation that calcium was able to inhibit the fungicidal activity as well as the uptake/binding of CAN-296, suggests that the mode of action of this novel antifungal agent may involve interaction with the cell wall of C. albicans.

Installing PACS--lessons learned

In 1997, Carson-Tahoe Hospital in Carson City, Nev., looked into the possibility of installing its own PACS system. Increased productivity was the main business goal the hospital hoped a PACS system would meet. Only two of three chosen vendors seriously considered the request to bid because of the small number of films produced by the hospital. After installation, the hospital identified the referring physicians who used the most film and then directed its marketing efforts to them. Lessons learned include the tremendous need for training of staff, referring physicians and radiologists. Expect everyone to be slow the first week the new system is running. Map out all processes to prepare for contingencies. Make plans for archiving and be flexible in assigning tasks--next week things may change. Consider bringing in an outside consultant to measure people's expectations and fears. After nearly a year, neither the technologists nor physicians express any regrets about the installation of PACS at Carson-Tahoe.

The biological significance of plasmalogens in defense against oxidative damage

The phospholipid class of plasmalogens is ubiquitously found in considerable amounts as a constituent of mammalian cell membranes and of plasma lipoproteins. Plasmalogens are more susceptible to oxidative reactions compared to their fatty acid ester analogues, due to the reactivity of their enolether function. Studies on plasmalogen-deficient cell lines lead to the proposal that these ether lipids serve as endogenous antioxidants. No clear conclusions regarding the antioxidative effects of plasmalogens could be drawn from studies in patients of different ages with peroxisomal deficiency disorders. A defective peroxisomal plasmalogen synthesis is not necessarily associated with other defects in the metabolism of peroxisomes, as has been established in a cell line recently. In different mammalian tissues a decrease of plasmalogens with age was described. Moreover, an accumulation of plasmalogen oxidation products was measured in brain of old cattle compared to young ones. In pathologic conditions associated with oxidative stress like in spinal cord ischemia and reperfusion, plasmalogen levels varied inversely according to the oxidative burden. Oxidation products of plasmalogens increased with time of ischemia in infarcted porcine heart tissue. Enrichment of lipoproteins with plasmalogens increased their oxidative resistance, which was diminished in the case of LDL particles in patients with coronary arteriosclerosis. In red cell membranes plasmalogens were reduced with donor age and in hyperlipidemia. Under lipid lowering therapy with lovastatin an increase was observed, indicating a possible antioxidative impact of this treatment. Taken together, there is good evidence that plasmalogens are effective as endogenous antioxidants. However, more experimental approaches not confounded by other lipolytic processes are needed to establish this role of plasmalogens.

Altered expression of microtubule-associated protein 1B in cerebral cortical structures of pentylenetetrazole-treated rats

Using Northern blot, immunoblotting, immunocytochemistry, and in situ hybridization, we show that a single administration of the convulsant pentylenetetrazole leads to robust, long-term changes in microtubule-associated protein 1B and its mRNA, in the adult rat brain. The first increases in MAP1B mRNA were detected at 15 hr following pentylenetetrazole administration in the temporal (Te2) and perirhinal cortex followed by increases in microtubule-associated protein 1B immunoreactivity at 72 hr postseizure. In contrast, the levels of microtubule-associated protein 1B mRNA and protein in layers I-II of the retrosplenial and parietal cortex (Par2) declined visibly by 24 hr and 72 h, respectively, post-seizure. The changes included loss of staining in layers I-II and development of structures resembling "strings-of-beads" along the fibers of projection neurons of layer V. The levels of microtubule-associated protein 1B mRNA in the entorhinal cortex peaked at later times (72 h), especially in layers II-III, and returned to control levels by 10 days. Whereas the levels of microtubule-associated protein 1B immunoreactivity in the retrosplenial and parietal cortex recovered by 5-10 days, it persisted at high levels through day 35 in layer V of the temporal cortex (Te2), layers II-III of the perirhinal cortex and layers I-II of the lateral entorhinal cortex. These results indicate that seizure activity leads to long-term upregulation of genes coding for structural elements that are characteristic of the immature brain such as microtubule-associated protein 1B.

Ageing of equine articular cartilage: structure and composition of aggrecan and decorin

In order to identify the pathological processes involved in the destruction of articular cartilage in arthritic diseases, it is first necessary to characterise the normal homeostasis of cartilage in a healthy joint. In particular, normal age-related changes in the biochemistry of cartilage complicate any comparisons that are made between diseased and healthy tissue. There are, however, no reports in the literature detailing the influence of ageing on the biochemistry of proteoglycans in equine articular cartilage. This study addresses the absence of such information by investigating the structure of aggrecan and decorin extracted from a wide age-range of full thickness equine tissue. The total glycosaminoglycan content of articular cartilage from the metacarpophalangeal joint remained relatively constant throughout life. In contrast, specific components such as hyaluronan increased in concentration with advancing age as did the content of a structural epitope present on keratan sulphate chains. There were also significant age-related changes in the sulphation pattern of chondroitin sulphate chains. The structure of the large aggregating proteoglycan (aggrecan) became more heterogeneous in size with increasing age and each of the subspecies of aggrecan identified in the extracts was shown to carry a hyaluronan binding region (G1) domain. All subspecies of aggrecan also expressed specific epitopes to keratan sulphate, chondroitin-4-sulphate and chondroitin-6-sulphate glycosaminoglycan chains. The structure of the small nonaggregating proteoglycan decorin and the aggrecan stabilising molecule link protein were demonstrated to be similar in size and charge to that reported for other species.

In vitro antifungal activity of CAN-296: a naturally occurring complex carbohydrate

The in vitro activity of a naturally occurring complex carbohydrate, CAN-296, was evaluated by testing 132 clinical and ATCC isolates of yeast and Aspergillus fumigatus, many of which were azole-resistant. The in vitro susceptibility tests were performed by standardized broth micro- and macrodilution methods and results were compared with those obtained for amphotericin B, fluconazole, ketoconazole, flucytosine and the pneumocandin L-733,560. All tested Candida species showed highly uniform susceptibility to CAN-296 at concentrations of 0.078 to 0.312 microgram/ml; non-albicans Candida were as susceptible to CAN-296 as the Candida albicans strains. Multi-azole-resistant Candida species were highly sensitive to CAN-296. Minimum inhibitory concentration measurements did not differ from minimum lethal concentrations by more than two-fold for all tested Candida species. Aspergillus fumigatus, on the other hand, showed only moderate susceptibility to CAN-296. The kinetics of the anti-Candida activity of CAN-296 was investigated by kill-curve experiments using C. albicans and C. glabrata and the results were compared with those obtain for amphotericin B. CAN-296 was found to be rapidly fungicidal in concentrations ranging from 4-16 fold the mean MIC value. The broad spectrum of anti-Candida activity together with the rapid fungicidal effect make this complex carbohydrate a promising agent for clinical use.

Increased expression of microtubule-associated protein 1B in the hippocampus, subiculum, and perforant path of rats treated with a high dose of pentylenetetrazole

A single administration of the convulsant pentylenetetrazole (PTZ) initiates a complex pattern of long-term changes in microtubule-associated protein 1B (MAP1B) expression across the hippocampal formation. Using Northern blot and in situ hybridization we show that the first increases in MAP1B mRNA were detected at 15 h following PTZ administration in the granule cells of the dentate gyrus and CA3 region of the hippocampus and reached a maximum at 44 h. The levels of MAP1B mRNA in the subiculum peaked at later times (5 days). At 72 h MAP1B immunoreactivity was mainly localized in the granule-cell bodies and dentate inner and midmolecular layer as well as in neuronal cell bodies and the stratum lucidum, including the mossy fiber pathway of the CA3 region. By 5-10 days the levels of MAP1B in the pyramidal cells in the CA3 region decreased to very low levels; rather, heavy staining of interneuron-like cells and "strings-of-bead" structures all over the hippocampus and at the stratum oriens/alveus border were seen. The levels of MAP1B in the hippocampus returned to control levels by 20 days after PTZ administration. MAP1B immunoreactivity in the alvear path was also evident at 5 days postinjection at the CA1/alveus border. The intensity of MAP1B staining increased gradually in the perforant path starting at 72 h and persisted at high levels until day 35. Our studies show that (i) MAP1B is a temporal and regional marker for rapid and acute epileptic seizures and (ii) long-term increases in MAP1B in the perforant path might play a role in PTZ-induced seizures.

IL-1 beta induces the degradation of equine articular cartilage by a mechanism that is not mediated by nitric oxide

Proteoglycan degradation was induced in young equine articular cartilage explants cultured for eight days in the presence of 50 ng/ml recombinant human interleukin-1 beta. Degradation was initiated after 6 hours of exposure to the cytokine. This was accompanied by an induction of nitric oxide synthesis and a decrease in the incorporation of [36S]sulphate into the glycosaminoglycan chains of proteoglycans. The addition of 1mM N-iminoethyl-L-ornithine (an inhibitor of nitric oxide synthase) to the explant cultures in the presence of rhIL-1 beta suppressed the synthesis of NO and restored proteoglycan synthesis to control levels. However, treatment of explants with LNIO did not overcome proteoglycan degradation. These results indicate that although IL1 beta regulates both proteoglycan synthesis and degradation in equine cartilage explants, only the inhibition of proteoglycan synthesis is mediated by nitric oxide.

Influence of age and treadmill running on motor performance in rats

The influence of treadmill running on age-dependent changes of motor performance was investigated in differently old female Sprague-Dawley rats. Following 12 months of exercise training a test battery including gait analysis, spontaneous motor activity, and three more motor tasks of different complexity was performed. The influence of age on motor performance depended on the complexity of the motor requirement. Simple tests were less affected by age than more complex ones. Treadmill running induced positive effects on the age-dependent impairment of various motor functions in middle-aged (14-18 months old) and aged (23-27 months old) rats. The positive influence of exercise training is explained by benefits of endurance training to the cardiovascular, neuromuscular, and central nervous systems.

The relationship between endothelin-1, event-related P300 potentials, and prognosis in cerebral arteriosclerosis

OBJECTIVES

To search for a potential role of endothelin-1 (ET-1), a potent vasoconstrictor and presumably neurotoxic 21-amino acid peptide, for dysfunction of brain signal processing and cerebrovascular morbidity in nondemented patients with cerebral arteriosclerosis.

DESIGN

Cross-sectional study with longitudinal follow-up.

SETTING

University-affiliated teaching hospital.

PARTICIPANTS

A total of 106 nondemented patients with significant stenosis of either the internal carotid (cAD, cases; n = 63, mean age +/- SD, 62 +/- 7 years) or peripheral arteries (pAD, disease controls; n = 43, 60 +/- 11 years) were investigated before carotid endarterectomy and bypass surgery, respectively. After a mean follow-up of about 19 months, cerebrovascular morbidity of the cAD and pAD patients was evaluated by phone.

MEASUREMENTS

Brain signal processing functions by event-related visual P300 potentials; cerebrovascular events by a structured telephone interview; the extent of arteriosclerosis by venous ET-1 concentration.

RESULTS

Venous ET-1 levels were elevated in both cAD and pAD patient groups, but to the same degree. In these patients, ET-1 concentration was correlated slightly with diastolic blood pressure (r = .334, P = .0326, stepwise regression). Only in cAD patients with ET-1 levels above the 75th percentile were P300 latencies markedly prolonged compared with their lower ET-1 level counterparts. Furthermore, the P300 latencies of the cAD patients, but not of the pAD patients, correlated positively with venous ET-1 concentration and inversely with pack years of smoking (r = .728, P = .0002; stepwise regression). In contrast to base-line P300 abnormalities and classical risk factors (e.g., hypertension), high ET-1 levels predicted an increased cerebrovascular morbidity of cAD, but not of pAD, patients (P = .0044; Mantel Cox test).

CONCLUSIONS

In nondemented patients with cerebral arteriosclerosis, endothelin-1 is associated with P300 abnormalities reflecting subclinical dysfunction of brain signal processing. In the long-term, high venous ET-1 levels also appear to predict a higher cerebrovascular morbidity of cAD patients even after carotid endarterectomy.

Chronic tenosynovitis of the carpal extensor tendon sheaths in 15 horses

The history, clinical features, radiological findings, treatment and outcome of 15 horses with chronic tenosynovitis of the carpal extensor tendon sheaths are reported. The condition was seen most commonly in horses used for jumping and penetration of the tendon sheaths by thorns was the most common aetiology. Treatment involved surgical resection of the hyperplastic synovial membrane, and adhesions within the tendon sheath, with primary closure. When combined with early postoperative physiotherapy this was found to be an effective method of treatment. All horses in this series were not lame at follow-up, with 14 horse returning to their former level of athletic performance.

Proteoglycan metabolism of equine articular chondrocytes cultured in alginate beads

Equine chondrocytes were cultured in vitro for 30 days in ionically gelled alginate beads. The alginate polymerises into a stable gel in the presence of divalent cations (calcium), and rapid depolymerisation in the presence of a calcium chelator releases the viable chondrocytes. The chondrocytes maintained a spherical appearance for 30 days in culture, in marked contrast to monolayer cultures, which develop a dedifferentiated fibroblastic morphology. The major proteoglycan molecule produced by the encapsulated chondrocytes was aggrecan, of similar hydrodynamic size to aggrecan molecules present in the matrix of the articular cartilage from which the cells were harvested. Link protein, keratan sulphate and chondroitin sulphate were also synthesised by the chondrocytes, as demonstrated by immunohistochemistry. The proteoglycan secreted by the chondrocytes consisted of at least two pools, one remaining adjacent to the cell and forming a dense, cell-associated matrix, and another migrating more peripherally into the intercellular compartment. Newly synthesised proteoglycans extracted from the pericellular matrix and the intercellular matrix were similar in hydrodynamic size and aggregated in the presence of exogenous hyaluronan.

V+ fibronectin mRNA is increased in the brains of aged rats: effect of food restriction

Food restriction increases life-span in rodents. With regard to the central nervous system, underfeeding has been shown to have beneficial effects on synaptic transmission in old rats. However, the molecular events underlying functional changes in the brains of food-restricted rats are largely unknown. In the present study the levels of fibronectin mRNA containing the alternatively spliced segment V (FN-V+) as well as the levels of FN mRNA containing the alternatively spliced segment EIIIB (FN-EIIIB+), were examined by RNA gel blot hybridization in the brains of 3-day-old, 24-day-old, 10-month-old, 18-month-old, 30-month-old ad libitum (AL) fed, 30-month-old food-restricted (FR), and 35-37-month-old, FR rats. The hybridization signal for the FN-EIIIB+ mRNA was relatively abundant at early postnatal stages but very few transcripts were detected in the brains of adult, AL rats. The transcripts coding for FN-V+ mRNA were moderately expressed in the brains of 3-day-old, 24-day-old, 10-month-old, and 18-month-old rats. However, the FN-V+ mRNA signal was then prominently increased (approx. 3-fold) in the brains of the 30-month-old, AL rats vs. 10-month-old, AL rats, and further increased (approx. 2-fold) in the brains of 30-month-old, FR, as compared to 30-month-old, AL rats. However, the levels of FN-V+ mRNA were slightly decreased in the brains of very old (35-37-month) FR rats vs. 30-month-old FR rats. The distribution of fibronectin messenger RNA and protein was also investigated by non-radioactive in situ hybridization and immunohistochemistry, respectively. The most prominent expression of FN-V+ messenger RNA was seen in neurons of the hippocampus, including the granule cells of the dentate gyrus, and in layers III and V of the cortex of 30-month-old, FR rats. FN immunostaining closely paralleled the distribution of FN mRNA and was confined to the neuronal cell periphery. The upregulation of fibronectin gene expression upon exposure to glucocorticoids is well documented. Prolonged food restriction, acting as a stress factor, combined with decreased plasticity of glucocorticoid regulatory responses in the aged rats could cause an increase in the levels of FN mRNA and protein in the brains of old, FR rats. Since FN has been shown to provide an adhesive substrate for extending neurites, we conclude that food restriction may potentiate synaptic plasticity, via glucocorticoid receptor binding elements of the FN gene, in the brains of old rats.