The noradrenergic innervation of the ovary in old rats

The influence of ageing on the noradrenergic innervation of the ovary was studied in female Wistar rats using high pressure liquid chromatography (HPLC) with electrochemical detection and catecholamine histofluorescence techniques. Old age was accompanied by a significant decrease in ovarian noradrenaline levels. In young animals (3-month-old) noradrenergic nerve fibres were distributed primarily to blood vessels and in lesser amounts to the interstitial glands. In aged animals (24-month-old) perivascular noradrenergic fibres were reduced by more than 40%; interstitial gland nerve fibres were reduced by approximately 20%. The possibility that impaired noradrenergic ovarian innervation occurring in old age may be in some way related with age-dependent failure in reproductive activity is discussed.

Age-related changes of dopamine sensitive cyclic AMP generation in the rat frontal cortex

The dopamine (DA) D-1 and D-2 receptors coupled to 3',5'-cyclic adenosine monophosphate (cAMP) generation were studied in membrane particles of the frontal cortex in young (3-month-old), adult (12-month-old) and aged (24-month-old) male Sprague-Dawley rats. Activation of D-1 receptors with DA, apomorphine or fenoldopam enhanced accumulation of cAMP in the frontal cortex of young rats. The stimulatory effect elicited by DA on cAMP generation declined by about 20% in adult rats. No further decline in cAMP accumulation was noticeable in aged animals. The response to dopaminergic agonists was blocked by the D-1 receptor antagonist SCH 29390 in the three age groups examined. The presence of D-2 receptors, negatively coupled to cAMP generation, was demonstrated by incubating frontal cortex membrane particles with SCH 23390 and then with DA. This inhibitory response, was also elicited with D-2 receptor agonists quinpirole or bromocriptine in the absence of SCH 23390 in which these compounds produced a decrease in cAMP. The decrease in cAMP caused following D-2 receptor stimulation was shown to be enhanced with age. No difference was observed between the three age groups of animals in the activation of cAMP production by forskolin. The present data suggest a selective decrease in the coupling between the D-1 receptor and cAMP generation in the frontal cortex of adult and aged rats and of an age-dependent increase in the coupling between the D-2 receptor and cAMP inhibition. The functional consequences of these biochemical changes may have important implications in the aging of the rat frontal cortex.

Age-related changes of the noradrenergic innervation of the uterine vasculature: a fluorescence histochemical study

Age-related changes in the density of the noradrenergic perivascular plexus supplying the uterine artery and its intrauterine branches were studied in rats 4, 12 and 24 months old using the glyoxylic acid fluorescence technique. Moreover, uterine noradrenaline levels were determined by means of high pressure liquid chromatography with electrochemical detection. No changes in the density of noradrenergic innervation or in uterine noradrenaline levels were noticeable in 12 month in comparison with 4 month rats. In contrast, a significant decrease in the density of the noradrenergic perivascular plexus of uterine artery and of its intrauterine branches as well as decrease in noradrenaline concentrations of uterine horns and cervix were observed in 24 month rats. The above findings indicate an age-related impairment of uterine noradrenergic innervation.

Effect of long term hydergine treatment on the age-dependent loss of mossy fibers and of granule cells in the rat hippocampus

The effects of senescence and of long-term Hydergine treatment on the density and pattern of mossy fibers and on the number of granule cells of the dentate gyrus were studied in the rat hippocampus. Timm's technique for the histochemical demonstration of tissue stores of zinc, associated with quantitative image analysis and microdensitometry, was used for the study of mossy fibers. Consistent with our previous studies, we observed an age-related reduction both in the area occupied by mossy fibers and in the intensity of Timm staining in the mossy fiber area. Moreover, the density of granule cells in the dentate gyrus of hippocampus was reduced with age. Hydergine administration (1 and 3 mg/kg/day, p.o.), started when the rats were 17 months old and continued for 4 months, significantly increased the area occupied by mossy fibers and the intensity of Timm staining in the hippocampus of senescent animals. Moreover, Hydergine treatment was found to counteract the age-dependent decrease in granule cell number in the dentate gyrus of the hippocampus. These findings suggest that treatment with Hydergine is effective in counteracting or in slowing down the morphological disorganization observable in the hippocampal formation with advancing age. Moreover, it is possible that the effects of Hydergine administration in elderly patients might be related to an effect at the level of the hippocampus.

Age-related changes of glutamate dehydrogenase in the rat hippocampus: an enzyme histochemical study

Enzyme histochemical techniques associated with microphotometry were used to evaluate the reactivity of glutamate dehydrogenase (GDH) in the hippocampus of young (3 month) adult (12 month) and old (26 month) male Sprague-Dawley rats. In young rats the highest level of enzymatic reactivity was found in the stratum oriens of the CA-1-CA-4 fields followed in descending order by the molecular layer of fascia dentata, and by the layer of mossy fibers. In all the layers investigated GDH reactivity was higher in adult that in young rats. The older animals exhibited lower GDH reactivity than adult rats in almost all of the layers and higher enzymatic reactivity than in young rats in the stratum oriens of the CA-1-CA-4 fields. The hippocampus is known to be involved in the acquisition of two-way avoidance learning and is thought to utilize glutamate as one of its main neurotransmitters. These data suggest a possible relationship between hippocampal glutamatergic transmission and impairment of acquisition of avoidance learning occurring with age. Moreover, the possibility that a decreased glutamate catabolism occurring in old rats may contribute to the neuronal loss described in the hippocampus of aged rats is discussed.

Evidence against the existence of GABA-B receptor sites in rat cerebrovascular tree

By the use of combined radioreceptor binding and autoradiographic techniques we attempted to analyse the biochemical characteristics and the anatomical localization of GABA-B receptors in sections of rat circle of Willis and pialarachnoid arteries. 3H-GABA in the presence of 40 microM isoguvacine and 2.5 mM CaCl2 was used to label GABA-B receptor sites. Sections of rat cerebellar cortex were also processed as a reference tissue. No specific 3H-GABA binding was detectable either in radioreceptor binding or autoradiographic experiments. In contrast, the ligand was bound to sections of cerebellar cortex in a manner consistent with the labelling of GABA-B receptor sites. These findings indicate that cerebrovascular physiological responses to GABA are not linked, in the rat cerebrovascular tree, to the activation of GABA-B receptors.

Pharmacological characterization of rat renal medulla dopamine-sensitive cyclic adenosine monophosphate generating system

The dopamine (DA) DA-1 and DA-2 receptors coupled to 3'-5'-cyclic adenosine monophosphate (cAMP) generating system were characterized in membrane particles of the rat kidney medulla. In confirmation of reports using central and other peripheral tissues, activation of DA-1 receptors with DA, apomorphine or SKF 82526 induced accumulation of cAMP. This effect was blocked by the DA-1 receptors antagonist SCH 23390 and by the other DA-2 receptor antagonists fluphenazine and haloperidol. DA-2 receptor responses coupled negatively to the cAMP generating system were obtained by incubating renal medulla membrane particles with DA or SKF 82526 together with SCH 23390. DA-2 receptor responses were also elicited with the receptor agonists quinpirole and bromocriptine in the absence of SCH 23390. These inhibitory effects on cAMP generation were abolished by the DA-2 receptor antagonist l-sulpiride. Our findings suggest that rat renal medulla contains DA DA-1 and DA-2 receptors similar to those found in brain and in other peripheral tissues. The physiological significance of these receptors, if any, should be established in future studies.

Autoradiographic localization of peripheral [3H]-hydergine binding sites

The anatomical distribution of the ergot derivative [3H]-hydergine (co-dergocrine mesylate) was analyzed by the use of an in vitro autoradiographic technique on frozen sections of rat heart, mesenteric and renal arteries, adrenal gland and kidney. In the heart, [3H]-hydergine was bound by atria and by myocytes of ventricles. In the arterial wall, the drug was bound primarily by the adventitia, by the adventitia-media border and by the intimal layer. The density of adventitial and adventitial-medial binding sites has an inverse relation with the diameter of mesenteric or renal vessels. In the adrenal gland, [3H]-hydergine was bound primarily by the medulla and, in lesser amounts, by the zona glomerulosa. In the kidney, the drug was localized within the arterial tree as well as in cortical tubules and in medullary collecting tubules. The above findings suggest that [3H]-hydergine is bound by various structures involved in the regulation of cardiovascular homeostasis. Interaction with these sites probably accounts for the antihypertensive action of hydergine.

Age-dependent nerve cell loss in the brain of Sprague-Dawley rats: effect of long term acetyl-L-carnitine treatment

The age dependent loss of nerve cells was investigated in 22 brain areas from young (3 month), adult (13 month) and old (25 month) Sprague-Dawley rats. As in previous studies, we observed an age-related neuronal loss primarily in the archicortex and in the hippocampus and in other subcortical structures (amigdaloid nucleus, pontine nuclei, cerebellar cortex). In sensory areas of cerebral cortex the neuronal loss was less marked. The effect of a 6 month treatment with acetyl-L-carnitine (ALCAR) on the number of nerve cells in the same brain areas was also investigated. ALCAR treatment began when the rats were aged 16 months. ALCAR treatment was able to counteract the age-dependent decrease in nerve cell number primarily in the temporal and occipital cortical areas, in the archicortex and hippocampus. The above findings suggest that long term ALCAR treatment may be effective in slowing down the age-related nerve cell loss in some rat brain areas.

Lactate dehydrogenase, succinate dehydrogenase and nucleotide tetrazolium reductase histochemical activities in the mesentric arteries and arterioles of young and old rats

Age-related changes of the metabolic characteristics of large, medium and small brances of the rat superior mesenteric artery were investigated in young (4 month) and old (25 month) male Wistar rats, using enzyme histochemical techniques. The following enzymatic activities were examined: lactate dehydrogenase (LDH) and succinate dehydrogenase (SDH); NADPH(2)-tetrazolium reductase (NADPHD) and NADH(2)-tetrazolium reductase (NADHD). The intensity of enzymatic reactions within the tunica media of the large, medium and small branches and within the tunica intima of the large and medium branches of the artery was assessed microphotometrically. In young rats the reactivity of enzymes investigated is similar in both the tunica media and the intima with the exception of SDH which reacts stronger in the media than in the intima. LDH and NADHD displayed the most intense reaction whereas SDH reaction was less intense. In old rats LDH and NADPHD reactivity decreased, SDH reactivity increased in the intima of large and medium branches; and SDH increased in the media of large branches. The possibility is discussed that an impaired endothelial function may represent one of the most consistent phenomena of aging of the superior mesenteric artery.

Age-related changes in adrenaline content of rat splanchnic blood vessels

The influence of ageing on the adrenaline content of the superior mesenteric artery and vein, renal artery and vein and portal vein was studied in 3-month- (young), 12-month- (adult) and 24-month-old (old) male Wistar rats using radioenzymatic assay for the measurement of catecholamine levels. Adrenaline concentrations were unchanged in the vascular wall of the blood vessels examined in adult rats, but were significantly decreased in the vascular wall of the superior mesenteric, renal and portal veins of old rats. In contrast, no age-dependent changes of adrenaline levels were found in the vascular wall of the superior mesenteric or renal arteries. The possibility that the loss of adrenaline concentrations in the venous vascular wall may be in some way related to the cardiovascular impairment occurring with age is discussed.

Autoradiographic localization of [3H]muscimol binding sites in rat stomach: evidence for mucosal GABAA receptors

The distribution in the rat stomach of specific [3H]muscimol binding sites, which show characteristics of GABAA receptors, was examined by light microscopic autoradiography. Silver grains representing specific binding were present both in the antrum and body, with highest densities in the muscle layers. A small fraction of the binding was confined to gland cells of the mucosa in the gastric body, rather than in the antrum. The label was not specifically concentrated at the myenteric ganglia. These findings, along with earlier data, suggests that the local GABA content may regulate not only the contractility, but also the secretory functions of the stomach via gastric GABAA receptors.

The noradrenergic innervation of spinal cord blood vessels in old rats

The density and pattern of the sympathetic noradrenergic innervation of the extramedullary and intramedullary blood vessels of the spinal cord was studied in 3-, 12- and 25-month-old male Wistar rats using combined catecholamine histofluorescence and quantitative image analysis techniques. The study of innervation of intramedullary vessels was accomplished in spinal cord-transected rats to avoid the interference of descending spinal monoamine fibres in the observations. No age-related changes in the density of noradrenergic innervation of the anterior spinal artery or of sympathetic fibres associated with spinal cord blood vessels occurred. These results suggest that unlike perivascular noradrenergic nerves supplying the cerebrovascular tree, the sympathetic innervation of spinal cord blood vessels does not undergo age-dependent changes. It cannot be excluded that the lesser vulnerability of the spinal compared to the cerebral vascular tree to certain kinds of age-related diseases, may depend on the unchanged sympathetic trophic regulation of spinal vessels with age.

Absence of right-left asymmetries in the rat hippocampus as demonstrated by Timm staining

Although biochemical and behavioural studies have shown right-left differences in several areas of the rat limbic system, some anatomical studies reported no significant right-left differences in several morphological parameters of the hippocampus. The purpose of the present study was to determine whether there are asymmetries in the micro-anatomy of the rat hippocampus by examining the intensity of Timm staining in various hippocampal fields and the area occupied by mossy fibres by the use of combined microdensitometric and quantitative image analysis techniques. Timm staining demonstrates the distribution of intrahippocampal association pathways because it is a histochemical marker of zinc and other heavy transition metals. There were no right-left differences in the density of Timm staining at the level of the dentate gyrus, in the dendritic layer of CA1 and CA2 fields, in the mossy fibre area or in the subiculum. These findings provide further evidence of a lack of morphological asymmetry in the rat hippocampus.

Predominant epithelial localization of type A gamma-aminobutyric acid receptor sites within rat seminal vesicles and prostate glands

In order to understand the role of the gamma-aminobutyric acid (GABA)-ergic system in the reproductive organs of the male, the biochemical characteristics and the autoradiographic localization of GABA type A (GABAA) receptor sites were studied in sections of the rat epididymis, seminal vesicles and prostate gland (lateral lobe) using 3H-muscimol as a ligand. No specific 3H-muscimol binding occurred in the epididymis. 3H-muscimol was bound to sections of seminal vesicles and prostate glands in a manner consistent with the labeling of specific GABAA receptors. Binding was saturable, reversible, with Kd values of 27.5 +/- 2.0 and 26.0 +/- 1.9 nmol/l and Bmax values of 230 +/- 21 and 160 +/- 13 fmol/mg protein for seminal vesicles and prostate glands, respectively. The rank order of potency of GABAergic drugs in inhibiting 3H-muscimol binding to sections of seminal vesicles and prostate glands was also consistent with the labeling of GABAA receptors. Autoradiography demonstrated the predominant accumulation of silver grains in the epithelium of seminal vesicles and prostatic glandular tissue. These findings further support the suggestion of a possible role of GABA in the male reproductive function. The predominant epithelial localization of GABAA receptors in the seminal vesicles and in the prostate gland allows us to hypothesize that GABA may be involved in the secretory activities of these glands.

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)

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.

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

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

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.

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.

3H-muscimol binding sites within the rat choroid plexus: pharmacological characterization and autoradiographic localization

By using combined radioreceptor binding and autoradiographic techniques, we were able to localize the GABA 'A' receptor agonist 3H-muscimol in the rat choroid plexus. Within sections of rat choroid plexus, 3H-muscimol was bound specifically with a KD of 37 nM and a Bmax of 253 pmol/mg tissue. These values are consistent with the labelling of GABA 'A' receptor sites. The autoradiographic studies demonstrated that 3H-muscimol was attached to the epithelium of the choroid plexus. The blood vessels of the plexus did not exhibit specific labelling. Examination of these data suggests the existence of GABAergic mechanisms which control cerebrospinal fluid production or flow.

Are muscarinic receptors present in rat pial or intracerebral vessels?

Experiments were performed to determine whether muscarinic receptors were present within rat pial or intracerebral vessels. Localization of muscarinic receptors was determined by autoradiography using [3H]-quinuclidinyl benzilate ([3H]-QNB) as a ligand on brain sections of the frontoparietal and the temporal cortex, the neostriatum and the hippocampus. [3H]-QNB was bound specifically to sections of rat brain in a manner consistent with the labelling of muscarinic receptors. A high density of muscarinic receptors was found primarily in the neostriatum, followed, in descending order, by the cerebral cortex and the hippocampus. However, no specific [3H]-QNB binding was observed at the level of either the pial or intraparenchymal vessels. On the basis of the present data, the existence of muscarinic receptors within rat pial arteries and arterioles, as well as within intracerebral vessels, seems to be highly questionable.

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.

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.

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.