Biomedical subjects

D Zaccheo

Publications and source records attributed to D Zaccheo.

At least 19 recordsLinked to original sources

PubMed1998

Opposite roles of apolipoprotein E in normal brains and in Alzheimer's disease.

We have characterized the interaction between apolipoprotein E (apoE) and amyloid beta peptide (Abeta) in the soluble fraction of the cerebral cortex of Alzheimer's disease (AD) and control subjects. Western blot analysis with specific antibodies identified in both groups a complex composed of the full-length apoE and Abeta peptides ending at residues 40 and 42. The apoE-Abeta soluble aggregate is less stable in AD brains than in controls, when treated with the anionic detergent SDS. The complex is present in significantly higher quantity in control than in AD brains, whereas in the insoluble fraction an inverse correlation has previously been reported. Moreover, in the AD subjects the Abeta bound to apoE is more sensitive to protease digestion than is the unbound Abeta. Taken together, our results indicate that in normal brains apoE efficiently binds and sequesters Abeta, preventing its aggregation. In AD, the impaired apoE-Abeta binding leads to the critical accumulation of Abeta, facilitating plaque formation.

Alzheimer Disease↗

PubMed1998

Sensitivity to ageing of the limbic dopaminergic system: a review.

The limbic system includes the complex of brain centres, nuclei and connections that provide the anatomical substrate for emotions. Although the presence of small amounts of dopamine (DA) in several limbic structures has been recognized for a long time, for many years it was thought that limbic DA represented a precursor of noradrenaline in the biosynthetic pathway of catecholamines. More recent evidence has shown that limbic centres and nuclei are supplied with a dopaminergic innervation arising from the ventral tegmental area (field A10) and in smaller amounts from the mesencephalic A9 field. The dopaminergic limbic system is sensitive to ageing. Parameters of dopaminergic neurotransmission (DA levels, biosynthetic and catabolic markers and DA receptors) undergo age-related changes which depend on the structure and species investigated and are characterized mainly by a decline of different parameters examined. In this paper, the influence of ageing on DA biosynthesis, levels, metabolism and receptors are reviewed in laboratory rodents, monkeys and humans as well as in cases of Alzheimer's disease and Parkinson's disease. The possibility that changes of dopaminergic neurotransmission markers in the limbic system are associated with cognitive impairment and psychotic symptoms affecting the elderly is discussed. Better knowledge of dopaminergic neurotransmission mechanisms in the so-called physiological ageing and in senile dementia may provide new insights in the treatment of behavioural alterations frequently occurring in old age.

Aging↗

PubMed1998

Autoradiographic localisation of muscarinic cholinergic receptor subtypes in human placenta.

The localisation of M1-M4 muscarinic cholinergic receptor subtypes was investigated in sections of normal human term placenta by light microscope autoradiography. Muscarinic cholinergic receptor subtypes were found almost exclusively in syncytiotrophoblast. Neither other cellular components of placenta, nor blood vessels were labelled. Quantitative analysis of the density of silver grains developed in sections incubated with the different protocols for labelling M1-M4 receptor subtypes, revealed that syncytiotrophoblast expresses all subtypes of muscarinic cholinergic receptor investigated. A higher density of binding sites was found in the apical than in the basal portion of syncytiotrophoblast. The demonstration of muscarinic cholinergic receptors in syncytiotrophoblast suggests that a cholinergic system may have a role in regulating transport of compounds from maternal to foetal interface.

Adult↗

PubMed1998

Early glycoxidation damage in brains from Down's syndrome.

In Down's syndrome, the presence of three copies of chromosome 21 is associated with premature aging and progressive mental retardation sharing the pathological features of Alzheimer disease. Early cortical dysgenesis and late neuronal degeneration are probably caused by an overproduction of amyloid beta-peptide, followed by an increased cellular oxidation. Interestingly, chromosome 21 codes for superoxide-dismutase and amyloid beta precursor resulting, in Down's syndrome, in an overflow of these gene products and metabolites. We studied Down's fetal brain cortex to evaluate the presence and amount of lipid and protein oxidation markers; moreover, we quantified two forms of glycation end products that are known to be involved in the process of cellular oxidation. All these parameters are significantly increased in Down's fetal brains in comparison to controls, providing the evidence that accelerated brain glycoxidation occurs very early in the life of Down's syndrome subjects.

Aldehydes↗

PubMed1998

Increased amyloidogenic secretion in cerebellar granule cells undergoing apoptosis.

Some clues suggest that neuronal damage induces a secondary change of amyloid beta protein (Abeta) metabolism. We investigated this possibility by analyzing the secretion of Abeta and processing of its precursor protein (amyloid precursor protein, APP) in an in vitro model of neuronal apoptosis. Primary cultures of rat cerebellar granule neurons were metabolically labeled with [35S]methionine. Apoptosis was induced by shifting extracellular KCl concentration from 25 mM to 5 mM for 6 h. Control and apoptotic neurons were then subjected to depolarization-stimulated secretion. Constitutive and stimulated secretion media and cell lysates were immunoprecipitated with antibodies recognizing regions of Abeta, full-length APP, alpha- and beta-APP secreted forms. Immunoprecipitated proteins were separated by SDS/PAGE and quantitated with a PhosphorImager densitometer. Although intracellular full-length APP was not significantly changed after apoptosis, the monomeric and oligomeric forms of 4-kDa Abeta were 3-fold higher in depolarization-stimulated secretion compared with control neurons. Such increments were paralleled by a corresponding increase of the beta-APPs/alpha-APPs ratio in apoptotic secretion. Immunofluorescence studies performed with an antibody recognizing an epitope located in the Abeta sequence showed that the Abeta signal observed in the cytoplasm and in the Golgi apparatus of control neurons is uniformly redistributed in the condensed cytoplasm of apoptotic cells. These studies indicate that neuronal apoptosis is associated with a significant increase of metabolic products derived from beta-secretase cleavage and suggest that an overproduction of Abeta may be the consequence of neuronal damage from various causes.

Amyloid beta-Peptides↗

PubMed1998

Dopamine D2-like receptors in the kidney of spontaneously hypertensive rats: a radioligand binding assay and light microscope autoradiography study.

1. Dopamine D2-like receptors were investigated in sections of kidney from male spontaneously hypertensive rats (SHRs) at 6 and 14 weeks of age using radioligand binding assay and autoradiographic techniques with [3H]-spiperone as a ligand. 2. Systolic blood pressure values were slightly higher in 6-week-old SHRs in comparison with age-matched normotensive Wistar-Kyoto (WKY) rats and considerably higher in 14-week-old SHRs in comparison with the other groups investigated. Renal dopamine levels were higher in SHRs aged 6 and 14 weeks in comparison with age-matched WKY rats. Noradrenaline concentrations were similar in 6-week-old SHRs and normotensive WKY rats, and increased slightly in SHRs aged 14 weeks. 3. The density of [3H]-spiperone binding sites was similar in SHRs and WKY rats at 6 weeks of age, and decreased in SHRs at 14 weeks in comparison with age-matched normotensive animals. Light microscope autoradiography revealed the accumulation of silver grains in the tunica adventitia, in the adventitia-media border of intrarenal arteries and within cortical tubules. A few specific silver grains were also developed in the glomerular tuft. No changes in the density and pattern of silver grains were noticeable between SHRs and WKY rats at 6 weeks of age, whereas a reduction in silver grains largely affecting vascular binding sites was observed at 14 weeks of age. 4. Renal denervation considerably decreased the density of [3H]-spiperone binding sites in sections of rat kidney, with an almost complete loss of vascular binding sites. 5. The above findings indicate the occurrence of a decrease of dopamine D2-like receptors in the kidney of SHRs with the progress of hypertension. Dopamine D2-like receptors which are mainly prejunctional are involved in the modulation of sympathetic neurotransmission in the kidney. The loss of these receptors in SHRs may contribute to the pathophysiology of hypertension.

Adrenergic alpha-Agonists↗

PubMed1998

Pharmacological characterization and autoradiographic localization of a putative dopamine D4 receptor in the heart.

1. The pharmacological profile and the anatomical localization of a putative dopamine D4 receptor were assessed in sections of rat and human atria and ventricles using combined radioligand binding and autoradiographic techniques with [3H]-spiperone as a ligand. 2. [3H]-Spiperone was bound specifically to sections of human and rat atria and ventricles. The binding was time-, temperature- and concentration-dependent, belonging to a single class of high-affinity sites. In atria, the dissociation constant value (Kd) was 0.45 nM in rats and 0.32 nM in humans, and the maximum density of binding sites (Bmax) was 31.6+/-2.9 fmol mg(-1) tissue in rats and 18.8+/-0.7 fmol mg(-1) tissue in humans. In ventricles, Kd was 0.38 nM in rats and 0.39 nM in humans, and the Bmax was 43.5+/-3.0 fmol mg(-1) tissue in rats and 56.4+/-3.2 fmol mg(-1) tissue in humans. 3. The pharmacological profile of [3H]-spiperone binding to sections of both rat and human atria and ventricles was consistent with the labelling of dopamine D2-like receptors. [3H]-Spiperone binding was more sensitive to displacement by the neuroleptic clozapine in sections of atria than of ventricles, suggesting the expression of a dopamine D4 receptor in atrial tissue. Moreover, preincubation of some sections with a dopamine D4 receptor antibody and subsequent exposure to [3H]-spiperone caused a remarkable decrease of radioligand binding to sections of atria, but only a slight reduction of binding to sections of ventricles. 4. Light microscope autoradiography revealed the accumulation of silver grains over atrial tissue within atrial myocardiocytes. A higher density of silver grains was developed in rat than in human atria. In ventricles, silver grains were accumulated primarily in cluster areas both in rats and in humans. 5. The above findings suggest the expression of a dopamine D4 receptor in rat atria, but not in ventricles. A similar site was identified in human atria. The possible relevance of a dopamine D4 receptor in the heart is discussed.

Adolescent↗

PubMed1997

Is amyloid beta-protein glycated in Alzheimer's disease?

Recent data suggest that protein glycation is involved in the process of amyloid formation in Alzheimer's disease (AD). To further investigate this issue, we analyzed the presence of advanced glycation end products (AGE) in soluble and insoluble forms of amyloid beta-protein (A beta) as well as in apolipoprotein E (apoE), a protein bound to amyloid deposits. Both proteins were extracted from cerebral cortex obtained from patients with AD and probed by immunoblotting with two antibodies specific for different AGE, already known to immunocytochemically label amyloid plaques. All the AGE antibodies failed to recognize either A beta or apoE, whereas they reacted with synthetic A beta glycated in vitro. These findings indicate that other proteins associated with amyloid deposits are candidates to be modified with AGE in Alzheimer's cerebral tissue.

Alzheimer Disease↗

PubMed1997

Muscarinic cholinergic receptor subtypes expression by human placenta.

The presence of a cholinergic system in the placenta is suggested by several data, but no information is available concerning cholinergic receptor expression by placenta. The present study was designed to investigate muscarinic cholinergic receptors in sections of human placenta using a radioligand binding techniques with [3H]N-methyl scopolamine ([3H]NMS) as a ligand. [3H]NMS was bound to sections of human placenta in a manner consistent with the labelling of muscarinic cholinergic receptors. The dissociation constant (Kd) value was 0.1 +/- 0.03 nM and the maximum density of binding site (Bmax) value was 10.82 +/- 0.09 fmol/mg of tissue. The binding was time-, temperature- and concentration-dependent, belonging to one class of high affinity sites. Analysis of [3H]NMS displacement curves by compounds acting on the different subtypes of muscarinic cholinergic receptor subtypes suggests that human placenta expresses the four subtypes (M1-M4) of muscarinic cholinergic receptor assayable with radioligand binding assay techniques. The demonstration of muscarinic cholinergic recognition sites in human placenta may contribute to define the possible significance of placental cholinergic system. Moreover, human placenta can be used as an easily obtainable human source of M1-M4 muscarinic cholinergic receptor subtypes.

Adult↗

PubMed1997

Muscarinic cholinergic receptors and acetylcholinesterase activity in umbilical artery and vein in pregnancy-induced hypertension (pre-eclampsia).

The influence of pregnancy-induced hypertension (pre-eclampsia) on muscarinic cholinergic receptors and on acetylcholinesterase (AChE) activity was investigated using frozen sections of the umbilical artery and vein. Pre-eclamptic patients undergoing Caesarean delivery and normotensive pregnant control woman undergoing Caesarean delivery with similar parity, gestation length and age were examined. Muscarinic cholinergic receptors were assayed in frozen sections of the umbilical artery and vein by a radioligand binding assay technique, using [3H]-N-methyl scopolamine (NMS) as a ligand. AChE was demonstrated with a histochemical technique associated with microdensitometry. [3H]-NMS was specifically bound to sections of both umbilical artery and vein in a manner consistent with the labelling of muscarinic cholinergic receptors. The affinity of the radioligand was similar in the two vessels, whereas the maximum density of binding sites (Bmax) was higher in the umbilical vein than in the artery. A faint AChE reactivity was observed in the tunica media of both umbilical artery and vein. In pre-eclampsia, a loss of [3H]-NMS binding sites not accompanied by changes in the affinity of radioligand was found. The decrease of muscarinic cholinergic receptors involved to a greater extent the umbilical artery than the vein. No differences in AChE activity were found at the level of umbilical artery and vein between control and pre-eclamptic subjects. These findings suggest that pre-eclampsia is characterized by a loss of muscarinic cholinergic receptors in the umbilical circulation not accompanied by changes of the acetylcholine catabolizing enzyme AChE. It is possible that the decreased density of vascular muscarinic cholinergic receptors in pregnancy-induced hypertension contribute to the increased resistance of the umbilical circulation occurring in pre-eclampsia.

Acetylcholinesterase↗

PubMed1996

Pharmacological characterization and autoradiographic localization of dopamine receptors in the rat adrenal medulla.

The pharmacological profile and the anatomical localization of dopamine D1-like and D2-like receptors were studied in sections of rat adrenal medulla, with radioligand binding and autoradiographic techniques, respectively. [3H]([R]-(+)-chloro-2,3,4,5-tetrahydro-5-phenyl-1 H-3benzazepin-al hemimaleate) (SCH 23390) was used as a ligand for dopamine D1-like receptors and [3H]spiperone was used as a ligand for dopamine D2-like receptors. Radioligand binding and light microscope autoradiography did not show specific [3H]SCH 23390 binding in sections of rat adrenal medulla. This suggests that rat adrenal medulla does not express dopamine D1-like receptors. [3H]Spiperone was specifically bound to sections of rat adrenal medulla. The binding was time-, temperature- and concentration-dependent, with a dissociation constant (Kd) of 1.05 nM and a maximum density of binding sites (Bmax) of 100.2 +/- 3.8 fmol/mg tissue. The pharmacological profile of [3H]spiperone binding to rat adrenal medulla was similar to that displayed by neostriatum, which is known to express dopamine D2 receptors. Light microscope autoradiography showed the accumulation of specifically bound [3H]spiperone as silver grains within sections of adrenal medulla. Silver grains were found primarily over the cellular membrane of chromaffin cells. The above data indicate that chromaffin cells of the rat adrenal medulla express dopamine receptors belonging to the dopamine D2 receptor subtype. These receptors are probably involved in the modulation of catecholamine release from chromaffin cells, as documented by functional studies.

Adrenal Medulla↗

PubMed1996

NADPH-diaphorase activity in brain macrophages during postnatal development in the rat.

NADPH-diaphorase histochemistry, that allows the visualization of cells producing the gaseous intercellular messenger nitric oxide, was used in the study of the forebrain during the first three postnatal weeks in the rat. Subpopulations of NADPH-diaphorase positive neurons were observed at all ages studied. In addition, non-neuronal NADPH-diaphorase-stained cells were detected in the subcortical white matter, and were very numerous in the supraventricular portion of the corpus callosum, and in the internal and external capsules. These cells were present during the first two postnatal weeks, and were especially prominent at the end of the first postnatal week. They were round-shaped and morphologically similar to the brain macrophages, whose phagocytic activity has been shown in previous studies to play a role in naturally occurring cell death and elimination of exhuberant axons. Series of sections adjacent to those stained with NADPH-diaphorase were processed with immunohistochemistry, using two different antibodies (OX-42 and ED-1) that detect macrophagic and microglial markers, and antibodies that recognize the neuronal form of nitric oxide synthase. Furthermore, brain sections from rats at postnatal day 7 were sequentially processed for either OX-42 or nitric oxide synthase immunohistochemistry followed by NADPH-diaphorase histochemistry. The morphological features and distribution of the non-neuronal NADPH-diaphorase-positive cells were superimposable to those obtained with OX-42 and ED-1 immunohistochemistry. In addition, these cells did not display nitric oxide synthase immunoreactivity. Double-labelled NADPH-diaphorase-positive and OX-42-immunoreactive cells were detected at postnatal day 7. The present results show that brain macrophages express NADPH-diaphorase activity during the early stages of the normal postnatal maturation and suggest that nitric oxide produced by brain macrophages could be involved in the development reshaping of the central nervous system.

Animals↗

PubMed1996

Isolated lung perfusion with platinum in the treatment of pulmonary metastases from soft tissue sarcomas.

A multimodality approach including operation and isolated lung perfusion with platinum was used in six patients with lung metastases from soft tissue sarcomas. Staged thoracotomies were used in two patients with bilateral lesions. The inclusion criteria generally applied for surgical excision were adopted in this study. The pulmonary artery and a portion of the left atrium were isolated from systemic circulation and cannulated. The cannulas were then connected to a perfusion circuit and normothermic isolated lung perfusion was done for 60 minutes. The lung was then flushed and metastasectomy was done. Serial blood (systemic and pulmonary), tissue (normal lung and tumor), and urine samples were obtained for platinum content measurement by flameless atomic absorption spectroscopy. Lung damage was assessed by light and electron microscopy examination and by serial respiratory tests. Isolated lung perfusion was accomplished in all patients without any death, operative complication, or systemic toxicity. After operation, interstitial and alveolar edema developed in two patients (48 hours after treatment), necessitating respiratory support in one case. Total platinum concentrations in pulmonary plasma were about 43 times greater than those in systemic plasma. No differences in platinum concentrations between normal lung and metastatic tissue were found. Thus the proposed isolated lung perfusion technique is feasible and safe enough to be offered as a valid model to study combined chemosurgical approaches in the treatment of lung metastases.

Adult↗

PubMed1996

Age-dependent changes in the expression of dopamine receptor subtypes in human peripheral blood lymphocytes.

The pharmacological profile and the density of dopamine D3 and D5 receptor subtypes expressed by human peripheral blood lymphocytes of subjects of different ages (ranging from 20 to 75 years) were assessed using radioligand binding techniques. Dopamine D3 receptor was assayed with [3H]7-hydroxy-N,N-di-n-propyl-2-aminotetraline ([3H]7-OH-DPAT) as a ligand. Dopamine D5 receptor was assayed using [3HIR]-(+)-(-chloro-2,3,4,5, tetrahydro-5-phenyl-1H-3-benzazepin-al-hemimaleate) ([3H]SCH 23390) as a ligand. The affinity and the pharmacological profile of [3H]7-OH-DPAT and [3H]SCH 23390 at dopamine D3 and D5 receptor, respectively, were similar in subjects of different ages. The density of dopamine D3 receptor binding sites was slightly decreased in subjects of 30-39 years in comparison with younger individuals. A remarkable loss of dopamine D3 receptor was then found between 40 and 49 years of age in comparison with younger subjects. A further slight decrease was noticeable between 50 and 59 years of age. The number of [3H]7-OH-DPAT binding sites was then stabilized after 60 years of age. The density of dopamine D5 receptor binding sites did not show age-dependent changes. The above findings indicate the occurrence of a decline in the density of lymphocyte dopamine D3 but not D5 receptor between adult and mature subjects. The possibility that dopamine D3 receptor assay in peripheral blood lymphocytes may represent a tool for investigating dopamine receptor function in aging and age-related neurological disorders is discussed.

Adult↗

PubMed1996

Presence of soluble amyloid beta-peptide precedes amyloid plaque formation in Down's syndrome.

Abnormal and excessive accumulation of the amyloid beta-peptide (A beta) in the brain is a major and common characteristic of all Alzheimer's disease (AD) forms irrespective of their genetic background. Insoluble aggregates of A beta are identified as amyloid plaques. These deposits are thought to form when the amount of A beta is increased in the brain parenchyma as a result of either overexpression or altered processing of the amyloid precursor protein (APP). Soluble A beta ending at carboxyl-terminal residue 40 (A beta 40) and, in lesser amount, the form ending at residue 42 (A beta 42), are normal products of the APP metabolism in cell cultures. Increased secretion of soluble A beta 42 has been observed in cells transfected with constructs modeling APP gene mutations of familial forms of AD (refs 4, 5). On the basis of these in vitro data it has been hypothesized that the presence of soluble A beta 42 plays a role in the formation of amyloid plaques. Subjects affected by Down's syndrome (DS) have an increased APP gene dosage and overexpress APP. Apparently because of this overexpression, they almost invariably develop amyloid deposits after the age of 30 years, although they are free of them at earlier ages. Moreover, it has been observed that A beta 42 precedes A beta 40 in the course of amyloid deposition in DS brain. Thus, DS subjects provide the opportunity to investigate in the human brain the metabolic conditions that precede the formation of the amyloid deposits. Here we report that soluble A beta 42 is present in the brains of DS-affected subjects aged from 21 gestational weeks to 61 years but it is undetectable in age-matched controls. It is argued that overexpression of APP leads specifically to A beta 42 increase and that the presence of the soluble A beta 42 is causally related to plaque formation in DS and, likely, in AD brains.

Adolescent↗

PubMed1995

Effect of long-term treatment with the dihydropyridine-type calcium channel blocker darodipine (PY 108-068) on the cerebral capillary network in aged rats.

The effects of treatment with the dihydropyridine Ca+2 antagonist darodipine (PY 108-068) on age-related changes in the cerebral capillary network was studied using alkaline phosphatase histochemistry with quantitative image analysis. The investigation was performed on male Wistar rats of 12 months (adult reference group) and 27 months. The 27-month-old rats consisted of two groups, the first of control untreated animals and the second of rats receiving an oral dose of 5 mg/kg/day of darodipine from the 21st to the 27th month. The cerebral areas examined included the frontal cortex, the occipital cortex, Ammon's horn of the hippocampus, and the dentate gyrus. The number and the average length of alkaline phosphatase-positive capillaries were decreased in old rats, when compared with adult rats. The intercapillary distance, which is considered as a sensitive parameter for capillary density was increased in aged rats in comparison to adult rats. The capillary diameter was increased slightly or unchanged in old rats. The Ammon's horn and the frontal cortex were the cerebral areas most affected by age-dependent changes of the capillary network. Treatment with darodipine increased the number and the average length of alkaline phosphatase-reactive capillaries and reduced the intercapillary distance and the diameter of cerebral capillaries in old rats. The pericapillary microenvironment of the Ammon's horn was the most sensitive to treatment with darodipine. The above results showed that treatment with darodipine is capable of counteracting some microvascular changes occurring in the brain of aged rats. This suggests that the blockade of dihydropyridine-type Ca2+ channels has a positive effect on the brain microvascular system and may counteract the impairment of pericapillary microenvironment occurring with aging.

Aging↗

PubMed1995

Effect of treatment with the dihydropyridine-type calcium antagonist darodipine (PY 108-068) on the expression of calbindin D-28K immunoreactivity in the cerebellar cortex of aged rats.

The influence of long term treatment with the dihydropyridine-type Ca2+ antagonist darodipine (PY 108-068) on age-dependent changes in calbindin D-28K immunoreactivity in the cerebellar cortex of male Wistar rats was assessed. In 12-month-old rats used as an adult reference group, specific calbindin D-28K immunoreactivity was found within the cytoplasm of Purkinje neurons and their dendritic processes. The number of Purkinje neurons displaying calbindin D-28K immunoreactivity was decreased in the cerebellar cortex of aged in comparison with adult rats. The pattern of calbindin D-28K immunoreactivity was similar in the cerebellar cortex of 24-month-old rats (aged), although a significant decrease in the intensity of immunoreactivity was noticeable. Treatment of aged rats with darodipine for 6 months increased the percentage of immunoreactive Purkinje neurons and the intensity of calbindin D-28K immunoreactivity in the cytoplasm of Purkinje neurons. Calbindin D-28K is a Ca2+ binding protein probably involved in the modulation of Ca2+ homeostasis. The observation of a positive effect of darodipine treatment on calbindin D-28K immunoreactivity in the cerebellar cortex suggests that manipulation of dihydropyridine-type Ca2+ channels may contribute to counter age-dependent changes of Ca2+ homeostasis.

Aging↗

PubMed1995

Identification of age-related changes of dopamine D1-like receptors in the rat cerebellar cortex.

The present study was designed to characterize the pharmacological profile of dopamine D1-like receptors in the rat cerebellar cortex and to assess if these receptor sites undergo age-related changes. Cerebella of young (3 months), adult (12 months), and old (27 months) male Wistar rats were examined by using radioligand binding techniques and light microscope autoradiography. The non-selective dopamine D1-like radioligand [3H]SCH 23390 was specifically bound to sections of rat cerebellum. The findings that dopamine displaced [3H]SCH 23390 binding in the submicromolar range suggest that labelling of a dopamine D5 (or D1B) receptor subtype. The affinity of [3H]SCH 23390 for dopamine D1-like receptors was similar in the cerebellar cortex of the three animal groups investigated, whereas radioligand binding techniques revealed a gradual age-related reduction of the density of binding sites. Light microscope autoradiography showed the localization of [3H]SCH 23390 binding sites primarily in the molecular layer and to a lesser extent in the Purkinje neuron layer of the cerebellar cortex. Aging was accompanied by a loss of [3H]SCH 23390 binding sites affecting mainly the molecular layer. The age-dependent loss of dopamine D1-like receptors is more pronounced if detected with radioligand binding techniques than with light microscope autoradiography. This suggests that the decrease of dopamine D1-like receptors observed in aging rat cerebellar cortex may depend in part on changes in the receptor expression and in part on cortico-cerebellar structural changes.

Age Factors↗