Search PubMed⌕ Search

Biomedical subjects

A S Basile

Publications and source records attributed to A S Basile.

At least 91 records · Page 5Linked to original sources
PubMed1989

GABAA receptor complex in an experimental model of hepatic encephalopathy: evidence for elevated levels of an endogenous benzodiazepine receptor ligand.

The involvement of the gamma-aminobutyric acidA (GABAA) receptor complex in the pathogenesis of hepatic encephalopathy was examined in thioacetamide-treated rats with fulminant hepatic failure. Partially purified extracts from encephalopathic rat brain were approximately three times more potent in inhibiting [3H]Ro 15-1788 binding to benzodiazepine receptors than identically prepared extracts from control rats. High levels of inhibitory activity were also found in extracts of plasma, heart, and liver from thioacetamide-treated rats. The inhibition of [3H]Ro 15-1788 binding by brain extracts appeared to be competitive and reversible and was unaffected by treatment with either proteolytic enzymes or boiling. Further, GABA significantly enhanced the potency of these extracts in inhibiting [3H]flunitrazepam binding. In contrast, no differences were found in radioligand binding to the constituent recognition sites of the GABAA receptor complex in well-washed brain membranes prepared from control and encephalopathic animals. These findings suggest that the recognition-site qualities of the constituent proteins of the GABAA receptor complex are unchanged in an experimental model of hepatic encephalopathy. However, significant elevations in the level of a substance or substances with neurochemical properties characteristic of a benzodiazepine receptor agonist may contribute to the electrophysiological and behavioral manifestations of hepatic encephalopathy.

Animals↗
PubMed1989

Characterization of the effects of AHN 086, an irreversible ligand of "peripheral" benzodiazepine receptors, on contraction in guinea-pig atrial and ileal longitudinal smooth muscle.

The effects of AHN 086 and its reversibly acting structural analogue Ro 5-4864 were studied in the spontaneously beating guinea-pig atria and field-stimulated guinea-pig ileal longitudinal smooth muscle in the presence and absence of dihydropyridine calcium channel modulators. The treatment of guinea-pig atria with AHN 086 followed by extensive washing did not alter contraction. However, AHN 086 (0.5 microM) potentiated (88%) the positive inotropic responses by BAY K 8644, an effect that was not reversed by extensive washing of the tissue. Higher concentrations of AHN 086 (greater than 2 microM) irreversibly inhibited the intropic, but not the chronotropic responses to BAY K 8644, nifedipine, and isoproterenol. Ro 5-4864 (10 microM) produced a reversible enhancement of the inotropic responses and block of the chronotropic responses to BAY K 8644. In guinea-pig ileal longitudinal smooth muscle, both AHN 086 and Ro 5-4864 reversibly inhibited field-stimulated contractions. Neither Ro 5-4864 nor AHN 086 affected the ability of nifedipine to inhibit field-stimulated contractions of ileal longitudinal smooth muscle. Treatment of intact atrial with 5 microM AHN 086 followed by extensive washing resulted in a significant inhibition (30-50%) of [3H]Ro 5-4864 binding to peripheral benzodiazepine receptors and of [3H]nitrendipine binding to voltage-operated calcium channels, but did not affect [3H]dihydroalprenolol binding to beta-adrenergic receptors on atrial membranes. The same treatment applied to intact ileal longitudinal smooth muscle affected neither [3H] (-)-quinuclidinyl benzilate binding to muscarine receptors nor [3H]nitrendipine binding, but did result in a significant inhibition (30-50%) of [3H]Ro 5-4864 binding to ileal longitudinal smooth muscle membranes.(ABSTRACT TRUNCATED AT 250 WORDS)

3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethy↗
PubMed1989

Electrophysiological actions of Ro5-4864 on cerebellar Purkinje neurons: evidence for "peripheral" benzodiazepine receptor-mediated depression.

The effects of Ro 5-4864 (4'-chlorodiazepam; the archetypic peripheral benzodiazepine receptor ligand) were examined on the electrophysiological responses of rat cerebellar Purkinje neurons maintained in vitro. Ro 5-4864 produced a biphasic response (consisting of an increase followed by a decrease in spontaneous firing) in approximately 50% of the neurons studied. The remaining neurons responded to Ro 5-4864 application with decreased spontaneous activity. The EC50 and IC50 values for the excitatory and depressant responses to Ro 5-4864 were 490 and 450 nM, respectively. Preincubation with PK 11195 [N-methyl-N-(methyl-1-propyl)chloro-2-phenyl-1-isoquinoline-3-carboxamid e; a peripheral benzodiazepine receptor antagonist] reduced the potency of Ro 5-4864 to inhibit cell firing in a competitive fashion, but did not alter Ro 5-4864-elicited excitations. A similar effect was observed with the monocarboxylic acid anion transport inhibitor UK 5099 [alpha-cyano-beta-(1-phenylindol-3-yl)acrylate]. In contrast, the increases in cell firing elicited by t-butylbicyclophosphorothionate (a GABA-gated chloride channel blocker) were enhanced 6-fold by coperfusion with both Ro 5-4864 and PK 11195. These findings suggest that the Ro 5-4864 induced depressions of Purkinje neuron spontaneous activity is mediated by peripheral benzodiazepine receptors, whereas the excitation may result from modulation of the gamma-aminobutyric acid-gated chloride ionophore.

Animals↗
PubMed1988

Modulation of neurotransmitter metabolism by dihydropyridine calcium channel ligands in mouse brain.

The regional concentrations of dopamine, serotonin, dihydroxyphenylacetic acid, homovanillic acid and 5-hydroxyindole acetic acid were measured in mouse brain following administration of the dihydropyridine calcium channel activator BAY K 8644, and antagonist, nifedipine. BAY K 8644 (1-8 mg/kg) produced dose- and time-dependent increases in dihydroxyphenylacetic acid, homovanillic acid and 5-hydroxyindoleacetic acid concentrations in the caudate, without altering dopamine and serotonin levels. No changes in 5-hydroxyindoleacetic acid concentration were observed in the raphe nuclei, hypothalamus, hippocampus and frontal cortex. Nifedipine (4 mg/kg) blocked BAY K 8644- (2 mg/kg) elicited increases in dihydroxyphenylacetic acid in the caudate. Furthermore, a higher dose of nifedipine (8 mg/kg) decreased dihydroxyphenylacetic acid and homovanillic acid, but did not affect dopamine, serotonin or 5-hydroxyindoleacetic acid concentrations, while a lower dose of nifedipine (2 mg/kg) significantly increased serotonin, 5-hydroxyindoleacetic acid and homovanillic acid, but did not affect dopamine and dihydroxyphenylacetic acid concentrations. The findings that both BAY K 8644 and nifedipine affect neurotransmitter metabolism in vivo in a dose-, time- and brain region-dependent manner, suggest that high-affinity dihydropyridine calcium channel binding sites play an important role in regulating neurotransmitter turnover in the central nervous system.

3,4-Dihydroxyphenylacetic Acid↗
PubMed1988

Regulation of renal peripheral benzodiazepine receptors by anion transport inhibitors.

The in vitro and in vivo regulation of [3H]Ro 5-4864 binding to peripheral benzodiazepine receptors (PBR) by ion transport/exchange inhibitors was studied in the kidney. The potencies of 9-anthroic acid, furosemide, bumetanide, hydrochlorothiazide and SITS as inhibitors of [3H]Ro 5-4864 binding to renal membranes were consistent with their actions as anion transport inhibitors (Ki approximately equal to 30 - 130 microM). In contrast, spironolactone, amiloride, acetazolamide, and ouabain were less potent (Ki = 100-1000 microM). Administration of furosemide to rats for five days resulted in a profound diuresis (approximately equal to 350% increase in urine volume) accompanied by a significant increase in PBR density (43%) that was apparent by the fifth day of treatment. Administration of hydrochlorothiazide or Ro 5-4864 for five days also caused diuresis and increased renal PBR density. Both the diuresis and increased density of PBR produced by Ro 5-4864 were blocked by coadministration of PK 11195, which alone had no effect on either PBR density or urine volume. The equilibrium binding constants of [3H]Ro 5-4864 to cardiac membranes were unaffected by administration of any of these drugs. These findings suggest that renal PBR may be selectively modulated in vivo and in vitro by administration of ion transport/exchange inhibitors.

4-Acetamido-4'-isothiocyanatostilbene-2,2'-disulfo↗
PubMed1988

Tissue specific regulation of "peripheral-type" benzodiazepine receptor density after chemical sympathectomy.

The characteristics of [3H]Ro 5-4864 binding to "peripheral" benzodiazepine receptors (PBR) in the central nervous system and peripheral tissues were examined after chemical sympathectomy with 6-hydroxydopamine (6-OHDA). One week after the intracisternal administration of 6-OHDA, the number of [3H]Ro 5-4864 binding sites (Bmax) in the hypothalamus and striatum increased 41 and 50%, respectively, concurrent with significant reductions in catecholamine content. An increase (34%) in the Bmax of [3H]Ro 5-4864 to cardiac ventricle was observed one week after parenteral 6-OHDA administration. In contrast, the Bmax of [3H]Ro 5-4864 to pineal gland decreased 48% after 6-OHDA induced reduction in norepinephrine content. The Bmax values for [3H]Ro 5-4864 binding to other tissues (including lung, kidney, spleen, cerebral cortex, cerebellum, hippocampus and olfactory bulbs) were unaffected by 6-OHDA administration. The density of pineal, but not cardiac PBR was also reduced after reserpine treatment, an effect reversed by isoproterenol administration. These findings demonstrate that alterations in sympathetic input may regulate the density of PBR in both the central nervous system and periphery in a tissue specific fashion.

Animals↗
PubMed1988

Characterization of stress-induced alterations in [3H] Ro5-4864 binding to peripheral benzodiazepine receptors in rat heart and kidney.

Inescapable tailshock has been shown to elicit a tissue specific decrease in the density of peripheral benzodiazepine receptors (PBR). We have now explored possible mechanisms that may be responsible for this phenomenon. An 80 minute session of inescapable tailshock produced a reduction in the binding of [3H] Ro5-4864 to renal membranes at 0, 1 and 2 hr after stress, with values returning to control (naive) levels within 24 hr. In cardiac membranes, statistically significant reductions were observed only at 2 and 4 hr after stress. The role of the pituitary-adrenal axis and the sympathetic nervous system in this phenomenon was assessed by subjecting adrenalectomized, hypophysectomized, 6-OHDA-treated or control (sham-operated or saline-treated) rats to inescapable shock. Neither adrenalectomy, hypophysectomy, nor 6-OHDA pretreatment altered the stress-induced reduction in renal PBR. However, the stress-induced decrease in renal PBR was blocked by pretreatment with clonazepam (1 mg/kg), a potent anxiolytic with low affinity for PBR.

Adrenalectomy↗
PubMed1988

Differential responsiveness of cerebellar Purkinje neurons to GABA and benzodiazepine receptor ligands in an animal model of hepatic encephalopathy.

The role of the GABA-benzodiazepine receptor complex in the pathogenesis of hepatic encephalopathy was investigated by recording the electrophysiological responses of single cerebellar Purkinje neurons from rabbits with hepatic encephalopathy due to galactosamine-induced fulminant hepatic failure. Both the GABAmimetic muscimol and the benzodiazepine receptor agonist flunitrazepam were 3-4 times more potent in depressing the spontaneous activity of Purkinje neurons from rabbits with hepatic encephalopathy than from control animals. Furthermore, qualitatively different responses of Purkinje neurons to benzodiazepine receptor antagonists (Ro 15-1788 and Ro 14-7437) were found in controls and rabbits with hepatic encephalopathy. These compounds markedly excited Purkinje neurons from rabbits with hepatic encephalopathy, but had either no effect (Ro 14-7437) or partially suppressed (Ro 15-1788) the spontaneous activity of neurons from control animals. In addition, incubation of Purkinje neurons from rabbits with hepatic encephalopathy with subthreshold concentrations of Ro 14-7437 reduced their sensitivity to muscimol, whereas treatment of control neurons with Ro 14-7437 had no effect on their sensitivity to muscimol. Finally, Purkinje neurons from hepatic encephalopathy and control rabbits displayed no difference in sensitivity to the depressant actions of the alpha-adrenoceptor agonist phenylephrine. These findings demonstrate a differential responsiveness of Purkinje neurons from an animal model of hepatic encephalopathy to ligands that interact with the GABA-benzodiazepine receptor complex. Furthermore, the observations made in this experimental model are consistent with the involvement of the GABA-benzodiazepine receptor complex in mediating hepatic encephalopathy, and provide a potential explanation for the reported efficacy of benzodiazepine receptor antagonists in ameliorating this syndrome.

Animals↗
PubMed1987

Regulation of dihydropyridine calcium antagonist binding sites in the rat hippocampus following neurochemical lesions.

The effects of catecholaminergic, cholinergic, serotonergic, and glutaminergic terminal destruction and neurotransmitter depletion on [3H]nitrendipine binding to rat brain membranes were determined using the neurotoxins 6-hydroxydopamine, 5,7-dihydroxytryptamine, and kainic acid and the neurotransmitter-depleting agent reserpine. Following intracisternal injection of 6-hydroxydopamine there were time-dependent increases (14-23%) in the density but not change in the affinity of hippocampal [3H]nitrendipine binding sites. 6-Hydroxydopamine significantly increased [3H]nitrendipine binding in the hippocampus 4 and 10 days following injection. However, no significant change in binding was observed at 16 and 26 days. [3H]Nitrendipine binding in the cerebral cortex, striatum, cerebellum, and brain stem was unaffected by 6-hydroxydopamine. Neither 5,7-dihydroxytryptamine nor kainic acid affected [3H]nitrendipine binding in the hippocampus and cerebral cortex. Acute and chronic reserpinization also did not affect [3H]nitrendipine binding in the hippocampus and cerebral cortex. These results indicate that dihydropyridine calcium antagonist bindings sites in rat brain are subject to brain region-specific regulation following neurochemical lesions and may be present in their largest densities on postsynaptic membranes.

Adrenergic Fibers↗
PubMed1987

Preservation of "peripheral" benzodiazepine receptors: differential effects of freezing on [3H]Ro 5-4864 and [3H]PK 11195 binding.

The equilibrium binding constants of [3H]Ro 5-4864 (a "peripheral" benzodiazepine receptor ligand) to renal membranes preserved by various freezing techniques were investigated. The Bmax for [3H]Ro 5-4864 binding to membranes from kidneys preserved as unwashed homogenates stored at -80, -20, or 5 degrees C, whole kidneys stores at -20 or 5 degrees C or as washed homogenate stored at -20 degrees C was significantly decreased (approximately 35%). Only when kidneys were frozen intact (using a dry-ice/acetone slurry) and stored at -80 degrees C was the density of [3H]Ro 5-4864 binding unchanged. However, the Bmax of [3H]PK 11195 (a putative "peripheral" benzodiazepine receptor antagonist) binding to renal membranes was unchanged following storage techniques that reduced the density of [3H]Ro 5-4864 binding 38%. No change was observed in the Kd values for [3H]Ro 5-4864 and [3H]PK 11195 binding to renal membranes preserved under any condition tested. These results demonstrate a method for the preservation of [3H]Ro 5-4864 binding to renal membranes, and suggests that [3H]Ro 5-4864 and [3H]PK 11195 bind to unique sites on or near the "peripheral" benzodiazepine receptor. [corrected]

Adrenalectomy↗
PubMed1987

"Peripheral" benzodiazepine binding sites in the Maudsley reactive rat: selective decrease confined to peripheral tissues.

"Peripheral" benzodiazepine binding sites (PBS) were studied in both the CNS and peripheral tissues of Maudsley reactive (MR) and Maudsley non-reactive (MNR) rats using the PBS specific ligand [3H]Ro 5-4864. A statistically significant reduction in the density of PBS was found in heart and kidney of the MR compared to the MNR. Similar reductions in the density of PBS were not observed in a number of areas of the central nervous system (including cortex, hippocampus, and hypothalamus) or other peripheral tissues, such as lung and adrenal. This selective decrease in PBS in a strain selectively bred for a high degree of "fearfulness" may be related to previous findings of a reduction in the density of PBS in the same tissues in rats subjected to uncontrollable shock. These observations suggest that PBS in heart and kidney may be altered in response to fear or anxiety.

Adrenal Glands↗
PubMed1987

Maximal electroshock increases the density of [3H]Ro 5-4864 binding to mouse cerebral cortex.

The effects of chemically and electrically-induced convulsions on the binding of [3H]Ro 5-4864 to peripheral benzodiazepine receptors (PBR) was studied in both peripheral tissues and the central nervous system (CNS). Acute, maximal electroshock (MES) increased the density of PBR in mouse cerebral cortex as evidenced by a 30% increase in the Bmax of this archetypic ligand. These values returned to control levels by 60 minutes after MES treatment. In contrast, thirty and sixty minutes after convulsions induced by Ro 5-4864, strychnine, or pentylenetetrazol, neither the Bmax nor Kd of [3H]Ro 5-4864 binding to mouse cerebral cortical membranes was altered. The increase in [3H]Ro 5-4864 binding to cortex observed 30 minutes after MES was blocked by anticonvulsant doses of phenobarbital, phenytoin and clonazepam. No changes in the characteristics of [3H]Ro 5-4864 binding was observed in cerebellar or hippocampal membranes 30 minutes following acute MES. Further, after long-term MES administration (1 treatment/day, 5 days), no change in PBR density could be detected 30 minutes after the last MES. Finally, while no change in PBR density was noted in the kidneys 30 minutes after the MES, a significant increase in PBR density was seen in the cardiac ventricles. These results demonstrate a selective modulation of PBR density by MES, suggesting that the PBR could be involved in either the generation of seizures or in postictal compensatory processes.

Animals↗
PubMed1987

Aldosterone-reversible decrease in the density of renal peripheral benzodiazepine receptors in the rat after adrenalectomy.

A statistically significant decrease in the density of peripheral benzodiazepine receptors was observed in renal membranes of rats beginning 2 weeks after adrenalectomy when compared with sham-operated controls. This decrease in peripheral benzodiazepine receptor density was manifest as a decrease in the maximum binding of two ligands, [3H]Ro 5-4864 and [3H]PK 11195, without accompanying changes in their Kd for this site. Similar changes were not seen in another aldosterone-sensitive organ, the submandibular salivary gland. The decrease in peripheral benzodiazepine receptor density observed in adrenalectomized rat renal membranes was restored to control levels after 1 week of aldosterone administration using a dose (12.5 micrograms/kg/day) that had no effect on peripheral benzodiazepine receptor density in sham-operated animals. In contrast, dexamethasone administration (50 micrograms/kg/day, 1 week) had no effect on renal peripheral benzodiazepine receptor density when administered to either adrenalectomized or sham-operated rats. Further, adrenal demedullation had no effect on renal peripheral benzodiazepine receptor density or affinity. The decrease in peripheral benzodiazepine receptor density was localized to the renal cortex and the outer stripe of the medulla by gross dissection of renal slices and renal tissue section autoradiography. The specific effect of adrenalectomy on renal peripheral benzodiazepine receptor density, the lack of direct effect of aldosterone on [3H] Ro 5-4864 binding and the localization of the change in peripheral benzodiazepine receptor density to the renal cortex and outer stripe suggest that these changes may reflect an adaptation of the renal nephron (possibly the distal convoluted tubule, intermediate tubule and/or the collecting duct) to the loss of mineralocorticoid hormones.

Adrenal Cortex↗
PubMed1986

Inescapable shock reduces [3H]Ro 5-4864 binding to "peripheral-type" benzodiazepine receptors in the rat.

[3H]Ro 5-4864 binding to "peripheral-type" benzodiazepine receptors was examined in brain and peripheral tissues of rats subjected to inescapable tailshocks. Two hours after a session of 80 (five-second) inescapable tailshocks, a significant reduction in [3H]Ro 5-4864 (10 mM) binding was observed in membranes from kidney (31%), cerebral cortex (29%), heart (19%) and pituitary (17%) compared to tissues from naive animals. In contrast, inescapable shock did not effect [3H]Ro 5-4864 binding to hippocampal, lung, or adrenal membranes. Scatchard analyses of [3H]Ro 5-4864 binding to renal membranes demonstrated that this session of tailshock reduced the density (Bmax) of "peripheral-type" benzodiazepine receptors without effecting the apparent affinity (Kd) of the radioligand for these sites. The effects of graded stress on [3H]Ro 5-4864 binding to cerebral cortex and kidney were investigated using 5, 20, or 80 (five-second) inescapable shocks. In cerebral cortical membranes, sessions of either 5 or 20 shocks did not affect, while 80 shocks reduced (29%) [3H]Ro 5-4864 (10 mM) binding. In renal membranes, 5 shocks significantly increased (35%), 80 shocks significantly decreased [3H]Ro 5-4864 (10mM) binding (31%). These findings demonstrate that the density of "peripheral-type" benzodiazepine receptors in both peripheral tissues and the central nervous system can be rapidly modulated by stress.

Analysis of Variance↗
PubMed1986

Characterization of benzodiazepine receptors in the bovine pineal gland: evidence for the presence of an atypical binding site.

Bovine and rat pineal benzodiazepine receptors were characterized using ligands with high affinities for either 'central-type' (CBR) or 'peripheral-type' (PBR) benzodiazepine receptors. The characteristics (Bmax = 83 +/- 10 fmol/mg protein, Kd = 3.88 +/- 0.46 nM) of benzodiazepine receptors in bovine pineal membranes measured with [3H]flunitrazepam (using flunitrazepam to define non-specific binding) were consistent with previously reported values. However, if non-specific binding was defined using Ro 15-1788 (a selective CBR ligand), the Bmax and Kd of [3H]flunitrazepam decreased 51 and 58%, respectively. In addition, when using PK 11195 to determine non-specific binding, the Bmax of [3H]flunitrazepam binding to bovine pineal decreased further (approximately 80%, Kd decreased approximately 39%). Together, these observations strongly suggested the presence of PBR in the bovine pineal. Bovine pineal PBR characterized with [3H]PK 11195 revealed a high density (relative to CBR) of high affinity binding sites (Kd = 1.08 +/- 0.30, Bmax = 776 +/- 33.0 fmol/mg protein). In contrast, when [3H]Ro 5-4864 (1-20 nM) was used to define PBR, no binding was detectable. These observations are in sharp contrast to the rat pineal gland, in which both [3H]Ro 5-4864 and [3H]PK 11195 bind to a large number of PBR with high affinity (Kd approximately equal to 1.9 nM, Bmax approximately equal to 26 pmol/mg protein). Bovine pineal PBR were further characterized with compounds structurally related to either Ro 5-4864 or PK 11195.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1986

Subcellular localization of "peripheral-type" binding sites for benzodiazepines in rat brain.

The binding of [3H]Ro 5-4864, a specific ligand for "peripheral-type" benzodiazepine binding sites and [3H]Ro 15-1788, a specific ligand for the central benzodiazepine receptors, was determined in subcellular fractions of rat brain. As previously reported, the highest levels of "peripheral-type" benzodiazepine binding sites and benzodiazepine receptors were found in the crude P1 and P2 fractions, respectively. Purification of these crude fractions revealed that high levels of both [3H]Ro 5-4864 and [3H]Ro 15-1788 binding were present in the mitochondrial and synaptosomal fractions. In contrast, the purified nuclei and myelin contained low levels of both [3H]Ro 5-4864 and [3H]Ro 15-1788 binding.

Animals↗