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F Amenta

Publications and source records attributed to F Amenta.

At least 199 records · Page 11Linked to original sources
PubMed1989

Autoradiographic localization of muscarinic receptors within the rat kidney.

We used a combination of radioreceptor binding and autoradiographic techniques to study the pharmacological characteristics and anatomical localization of [3H]quinuclidinyl benzylate (QNB) in kidney sections of Wistar-Kyoto (WKY) and spontaneously hypertensive rats (SHR). [3H]QNB was bound by sections of rat kidney in a manner consistent with the labeling of muscarinic acetylcholine receptors. Anatomically, these receptor sites were located primarily within the smooth muscle of the renal vascular tree and to a lesser extent within cortical and medullary tubules. The density of renal muscarinic acetylcholine receptors (both vascular and tubular) was decreased in hypertension but the affinity of the ligand for muscarinic receptors was unchanged. A possible role of muscarinic acetylcholine receptors in renal function is suggested.

Animals↗
PubMed1989

GABAA receptors in the rat stomach may mediate mucoprotective effects.

The occurrence and characteristics of binding sites specific for gamma-aminobutyric acid (GABA) and muscimol in the rat stomach were examined by biochemical and autoradiographic techniques, and the effects of GABAergic model compounds on gastric ulceration induced by chemical irritation was studied in intact and unilaterally vagotomized rats. Specific binding sites for [3H]GABA and [3H]muscimol, which showed the characteristics of GABAA receptors, were demonstrated on gastric membranes. Specific muscimol binding sites were found in all regions of the stomach and were present in both the mucosal layer and the remaining tissue of the stomach. Oral pretreatment of the rats with GABA, selective GABAA receptor agonists, or inhibitors of GABA degradation protected the gastric mucosa against the ulcers induced by acidified ethanol (chemical irritant), in both intact and vagotomized rats. These findings are consistent with the view that a subpopulation of GABAA receptors in the rat stomach may mediate the anti-ulcer effect.

Administration, Oral↗
PubMed1989

Acetyl-L-carnitine reduces the age-dependent loss of glucocorticoid receptors in the rat hippocampus: an autoradiographic study.

Brain autoradiography in adrenalectomized rats injected with 3H-corticosterone 2 hr before sacrifice was used to study the effect of aging and long-term acetyl-l-carnitine treatment on the hippocampal glucocorticoid receptor. Densitometric analysis of silver grains in individual nerve cells of the hippocampus showed that pyramidal neurones of the CA1 field and granular cells of the dentate gyrus are richest in 3H-corticosterone binding sites, whereas pyramidal neurons of the CA3 field have the lowest number of binding sites. There was a significant decline in the number of glucocorticoid receptors within the various hippocampal areas, both as the total number of 3H-corticosterone binding sites and as the number per single pyramidal or granule neuron associated with aging and perhaps due to loss of adrenocorticoid-competent neurons. The dentate gyrus and the CA1 region were mostly affected by the age-dependent decrease in glucocorticoid receptors of the hippocampus. Twenty-eight-month-old rats, treated with acetyl-l-carnitine for 7 months, showed a significantly higher number of 3H-corticosterone binding sites within the various hippocampal regions examined than did age-matched controls. The CA1 and the dentate gyrus were the regions most susceptible to amelioration by acetyl-l-carnitine treatment. These findings suggest a positive effect of acetyl-l-carnitine treatment on age-related changes which occur in the hippocampus.

Acetylcarnitine↗
PubMed1989

Enzyme histochemistry of glutamate dehydrogenase in ageing rat cerebellar cortex.

The influence of ageing on glutamate dehydrogenase activity was studied in the cerebellar cortex of 3-month-old (young), 12-month-old (adult) and 26-month-old (aged) male Sprague-Dawley rats by using an enzyme histochemical technique. In young rats the enzyme reactivity was observed in the neuropil of the molecular layer as well as in the perikarya of basket cells and of stellate cells; within the cytoplasm of Purkinje neurons and in synaptic glomeruli of the granular layer. Glutamate dehydrogenase activity was significantly increased in the cerebellar cortex of adult rats and decreased in old animals. The synaptic glomeruli of the granular layer were the structures of the cerebellar cortex more remarkably affected by age-related changes. The possibility that decreased glutamate catabolism occurring in the ageing cerebellar cortex may result in an excess of the amino acid and may contribute to the nerve cell loss occurring in the cerebellum of old rats is discussed.

Aging↗
PubMed1989

Autoradiographic localization of vasoactive intestinal polypeptide receptors in the rat mesenteric vascular tree.

By the use of combined in vitro radioreceptor binding and autoradiographic techniques, we analyzed the pharmacological properties and the anatomical localization of the vasoactive intestinal polypeptide (VIP) receptor in rat superior mesenteric artery and in medium and small mesenteric artery branches. 125I-VIP was bound by sections of rat superior mesenteric artery in a manner consistent with the labeling of specific VIP receptors, with Kd and Bmax values of 0.23 nM and 0.71 pmol/mg protein respectively. Inhibition of 125I-VIP binding with VIP and related peptides gives the following rank order of potency: VIP greater than peptide histidine methionine greater than secretin. Light microscope autoradiography reveals specific VIP binding sites within the medial layer of superior mesenteric artery and its branches. Medium and small sized vessels are richer in 125I-VIP binding sites than the larger ones.

Animals↗
PubMed1989

Age-related changes of the mossy fibre system in rat hippocampus: effect of long term acetyl-L-carnitine treatment.

Age-related changes of the hippocampal mossy fibre system were studied in rats of different ages (4, 12, and 24 months) using the Timm's histochemical technique for the detection of tissue stores of zinc and heavy transitional metals. Quantitative image analysis and microdensitometry techniques were applied for the evaluation of the changes themselves. The area occupied by mossy fibres and the intensity of Timm's staining in field CA3 of hippocampus were greater in adult rats than in young and old animals. These findings are consistent with previous behavioural data indicating that young and old rats exhibited a reduced passive avoidance learning with respect to adult animals. The above techniques were also used in a second session of this study designed to investigate the effect of a 6-months treatment with acetyl-L-carnitine (ALC) on the hippocampal mossy fibre system. ALC was found to increase significantly the area occupied by mossy fibres and the intensity of Timm's staining in the hippocampus of old rats. These findings are in agreement with and support from an anatomical point of view, the data indicating that long-term treatment with ALC improves passive avoidance performance.

Acetylcarnitine↗
PubMed1989

Binding of [3H]-muscimol to GABAA sites in the guinea-pig urinary bladder: biochemical assay and autoradiography.

1. The specific binding of [3H]-muscimol, a gamma-aminobutyric acidA receptor (GABAA) agonist, to whole membranes of the guinea-pig urinary bladder was examined. In addition, the distribution of specific muscimol binding sites within the bladder was visualized by autoradiography. 2. It was demonstrated that in a frozen-thawed whole membrane preparation of the organ the specific binding of [3H]-muscimol is reproducible, reversible and saturable. 3. Saturable binding was of a single component with an equilibrium dissociation constant (Kd) of 12 nM and a maximal density (Bmax) of about 80 fmol mg-1 protein. 4. In displacement experiments with several model compounds, [3H]-muscimol binding sites showed the characteristics of a GABAA receptor site. 5. Autoradiographic experiments revealed uneven distribution of specifically bound [3H]-muscimol in the bladder. The density of binding sites was high in clusters within the smooth muscle layers of the bladder fundus and of the urethra, while the apex and the neck were not specifically labelled. 6. The present findings show that GABAA type receptor sites in the guinea-pig urinary bladder may be labelled by [3H]-muscimol in a specific and reproducible manner. Moreover, the localization of these binding sites is consistent with the presence of GABAA receptors in only a subpopulation of vesical ganglia.

Animals↗
PubMed1989

Effect of acetyl-L-carnitine treatment on the density of muscarinic receptors in the brain of methylazoxymethanol-microencephalic rats.

The effect of methylazoxymethanol (MAM), administered on the 15th gestational day, on the density and pattern of muscarinic cholinergic receptors in some brain areas was assessed using combined radioreceptor binding and autoradiographic techniques. The effect of 15 days' treatment with acetyl-L-carnitine on the same parameter was also assessed. The density of muscarinic cholinergic receptors was found to be increased in the brain of MAM-microencephalic rats. Acetyl-L-carnitine administration caused a significant reduction in the density of receptors under study. A possible role of acetyl-L-carnitine in restoring central cholinergic neurotransmission is discussed.

Acetylcarnitine↗
PubMed1989

Effect of acetyl-L-carnitine treatment on brain ribonucleic acid levels in methylazoxymethanol-microencephalic rats.

The effects of methylazoxymethanol acetate (MAM) administered on the 15th gestational day, and of acetyl-L-carnitine treatment, on rat brain total and ribosomal RNA levels, were studied. In the brain of MAM-treated rats both total and ribosomal RNA concentrations were significantly reduced. Acetyl-L-carnitine treatment restored total and ribosomal RNA levels. The frontal cortex and the hippocampus were the brain areas most sensitive to acetyl-L-carnitine administration. Histochemical demonstration of tissue stores of nucleic acids showed that the loss of RNA induced by MAM occurs primarily within the cytoplasm of nerve cells in various telencephalic areas. Neuronal cytoplasmatic RNA is also sensitive to acetyl-L-carnitine treatment.

Acetylcarnitine↗
PubMed1989

Evidence from functional and autoradiographic studies for the presence of tubular dopamine-1 receptors and their involvement in the renal effects of fenoldopam.

Evidence from receptor-ligand binding and biochemical studies seems to suggest the possible existence of tubular dopamine DA-1 receptors in the rat kidney. However, it is not yet clear whether these putative tubular DA-1 receptors are involved in the functional renal responses elicited during the administration of DA and DA receptor agonists. In the present study we have examined the renal effects of several doses of selective DA-1 receptor agonist fenoldopam in pentobarbital-anesthetized rats in an attempt to unmask a direct tubular DA-1 receptor-mediated diuresis and natriuresis. Additionally, we have performed receptor-ligand binding and autoradiographic studies to examine the presence and localization of DA-1 receptors in various regions of the rat kidney. At the highest dose studied (2 micrograms/kg/min), fenoldopam produced diuresis and natriuresis, which was accompanied by a significant decrease in blood pressure and also a significant increase in glomerular filtration rate. At 1 micrograms/kg/min, the diuretic and natriuretic effects of fenoldopam were observed in the absence of any changes in blood pressure and glomerular filtration rate, but there was a significant increase in renal blood flow. However, at 0.5 micrograms/kg/min, fenoldopam-induced natriuresis and diuresis was not accompanied by any changes in blood pressure, renal blood flow or glomerular filtration rate, implying a direct tubular effect. These effects of fenoldopam appear to be mediated via activation of DA-1 receptors, because they were antagonized by the selective DA-1 antagonist SCH 23390.(ABSTRACT TRUNCATED AT 250 WORDS)

2,3,4,5-Tetrahydro-7,8-dihydroxy-1-phenyl-1H-3-ben↗
PubMed1988

An increase in the expression of neuropeptidergic vasodilator, but not vasoconstrictor, cerebrovascular nerves in aging rats.

Perivascular nerve fibres containing noradrenaline (NA), serotonin (5-HT), substance P (SP), vasoactive intestinal polypeptide (VIP), neuropeptide Y (NPY) and calcitonin gene-related peptide (CGRP) were localized in whole-mount stretch preparations of the arteries of the rat circle of Willis using fluorescence and immunohistochemical techniques. Changes in the pattern and density of these perivascular nerves were studied from birth to 27 months of age. All perivascular nerve types reached a peak density of innervation at 1 month of age. This was followed by a general fall in the density of fluorescent nerve fibres. However, with aging, there was a decrease in the expression of vasoconstrictor neurotransmitters (NA and 5-HT) in cerebrovascular nerves, whereas the expression of vasodilator neurotransmitter (VIP and CGRP) in perivascular nerve fibres supplying the rat cerebral arteries was strikingly increased in old age. The density of NPY- and SP-containing nerve fibres was not significantly altered in old age. These changes are discussed in relation to the increased incidence of cerebrovascular disorders in the elderly.

Aging↗
PubMed1988

Presence of dopamine-dependent adenylate cyclase activity in human renal cortex.

The effects of dopamine (DA) and of two selective DA DA1 agonists (SKF 38393 and SKF 82526) on adenylate cyclase activity were studied with human kidney cortex membrane preparations. DA elicited a dose-related stimulation of adenylate cyclase activity with an EC50 of 60 microM. The selective DA DA1 antagonist SCH 23390 behaved as a competitive antagonist, shifting the dose-response curve to the right. The non-selective beta-adrenoceptor antagonist (-)-propranolol did not affect the EC50 of the dose-response curve to DA but attenuated the maximal stimulatory effect of DA at concentrations higher than 100 microM. (+)-Sulpiride inhibited DA-induced adenylate cyclase stimulation in a dose-dependent manner with an IC50 of 4.6 X 10(-8) M but (-)-sulpiride was without effect. Both SKF 38393 and SKF 82526 stimulated the adenylate cyclase activity of human kidney cortex; this effect was completely antagonized by SCH 23390. Our results, demonstrating the presence of DA-sensitive adenylate cyclase activity, strongly suggest the presence of a DA receptor of the DA1 subtype in human kidney cortex.

Adenylyl Cyclases↗
PubMed1988

Age-related changes in vasoactive intestinal polypeptide levels and distribution in the rat lung.

Vasoactive intestinal polypeptide (VIP) levels and distribution were studied in the lung of young-adult (3-month-old) and aged (28-month-old) male Wistar rats by radioimmunoassay and immunofluorescence. VIP concentrations were reduced approximately by 60% as the animal ages. The density of VIP-immunoreactive nerve fibres was remarkably reduced within bronchial smooth muscle and bronchial glands. Moreover, the number of VIP-immunoreactive nerve cell bodies located in intraparenchymal ganglia was decreased in old rats. The density of VIP-containing perivascular plexuses was slightly reduced in senescence. The present data are indicative that VIP neuronal system is impaired in the lung of old rats. In view of the significant age-dependent loss of VIP-immunoreactive nerve fibres that supply the bronchial tree and bronchial glands it cannot be excluded that the relaxant action exerted by peptide on airway smooth muscle and the control of bronchial secretion exerted by VIP are impaired in old age.

Aging↗
PubMed1988

Age-related changes of the metabolic profile of rat cerebellar cortex: enzyme histochemical study.

The influence of aging on the metabolic profile of cerebellar cortex was studied in young (3-month-old), adult (12-month-old) and aged (26-month-old) male Sprague-Dawley rats using enzyme histochemical techniques. The following enzymatic activities related to energy transduction were examined: lactate-(LDH) and succinate-(SDH) dehydrogenases; NADH2-tetrazolium reductase (NADHD) and alpha-glycerophosphate-dehydrogenase (GPDH). The intensity of enzymatic staining within the neuropil of molecular and granular layers as well as within the cytoplasm of Purkinje neurons of young, adult and aged animals was assessed microphotometrically. In the molecular layer LSH, SDH and NADHD levels were reduced in old rats; GPDH was decreased both in adult and old animals. In Purkinje neurons no age-related changes of the enzymatic activities under study were observed. In the granular layer LDH and GPDH showed an age-dependent loss; SDH and NADHD were unchanged. The possibility that age-related changes of the enzymatic activities under study may be due to impaired energy production mechanisms and/or represent the consequence of reduced energetic needs resulting from the documented age-dependent loss of synapses in the molecular or in the granular layers of cerebellar cortex is discussed.

Aging↗
PubMed1988

Age-related changes of noradrenergic innervation of rat splanchnic blood vessels: a histofluorescence and neurochemical study.

The influence of ageing on the noradrenergic innervation of superior mesenteric artery and vein, renal artery and vein, and portal vein was studied in male Wistar rats by means of catecholamine histofluorescence, image analysis techniques and high pressure chromatography with electrochemical detection. Old age was accompanied by a marked increase in the density of noradrenergic innervation and an increase of noradrenaline levels in superior mesenteric artery, renal artery, and portal vein. In contrast, no significant age-related changes were observed in the density of noradrenergic innervation or in noradrenaline levels in superior mesenteric and renal vein. The present data indicate that, at least in superior mesenteric and renal artery and portal vein, senescence is not accompanied by loss or by lack of change in the noradrenergic innervation as commonly believed to be the case in many vascular trees. On the basis of our findings it cannot be excluded that increased plasma catecholamine levels observed in senescence derive, in part, from perivascular sympathetic endings.

Adrenergic Fibers↗
PubMed1988

Identification of beta-adrenergic sensitive adenylate cyclase in rat thoracic duct.

The effect of L-isoproterenol on the 3',5'-cyclic adenosine monophosphate (cAMP) generating system in rat thoracic duct membranes was investigated in order to identify beta-adrenergic receptors. L-Isoproterenol elicited a dose-dependent stimulation of cAMP formation; L-noradrenaline was less effective than L-isoproterenol in stimulating cAMP increase, whereas L-phenylephrine was without important effects on cAMP levels. L-Propranolol, a selective antagonist of beta-adrenergic receptors, caused a dose-dependent decrease of the effects of L-isoproterenol. In contrast, the L-isoproterenol-elicited increase of cAMP was unaffected by the alpha-adrenergic and dopamine receptor-blocking agents phentolamine and haloperidol. These data indicate that L-isoproterenol stimulates cAMP formation in the rat thoracic duct by a specific interaction with beta-adrenergic receptors positively coupled to adenylate cyclase.

Adenylyl Cyclases↗
PubMed1988

Age-related changes in the noradrenergic innervation of the coronary arteries in old rats: a fluorescent histochemical study.

Age-related changes in the density of the noradrenergic perivascular plexus supplying the coronary vessels in the rat were studied using the glyoxylic acid fluorescence technique. A marked decrease in the density of the noradrenergic innervation of large, medium and small size coronary arteries was observed in 25-month-old rats. In contrast, the fluorescent nerves supplying the coronary veins were not decreased in old animals. The present data are indicative of an age-related reduction of fluorescent noradrenergic nerves in the rat coronary arteries.

Aging↗