PubMed Health⌕ Search

Biomedical subjects

R D Ciaranello

Publications and source records attributed to R D Ciaranello.

At least 55 records · Page 3Linked to original sources
PubMed1987

[3H]dihydroergotamine as a high-affinity, slowly dissociating radioligand for 5-HT1B binding sites in rat brain membranes: evidence for guanine nucleotide regulation of agonist affinity states.

[3H]Dihydroergotamine (DE) labels a population of binding sites in rat brain membranes with an affinity of approximately 70 pM in both hippocampus (maximal binding at saturation [Bmax] = 340 fmol/mg of protein) and cerebral cortex (Bmax = 250 fmol/mg of protein). Specific binding typically comprises about 97% of total binding at the Kd of the radioligand when nonspecific binding is determined in the presence of 100 nM unlabeled DE. Association kinetics at 37 degrees C are consistent with a uniform association rate constant for all sites labeled. Specific binding is completely reversible with addition of excess unlabeled DE, but dissociation does not proceed with simple first-order kinetics, suggesting the presence of more than one discrete binding site. Competition studies with selective drugs reveal alpha adrenergic, 5-HT1A and 5-HT1B components of [3H]DE specific binding. When phentolamine (500 nM) is included to block alpha receptors and DPAT (100 nM) or spiroxatrine (500 nM) is included to block 5-HT1A receptors, specific binding is exclusively to sites with drug affinities characteristic of 5-HT1B receptors. Under these 5-HT1B-selective conditions, [3H]DE binding is about 90% specific, with a Kd of about 50 to 60 pM and a Bmax of 96 fmol/mg of protein in hippocampus and 77 fmol/mg of protein in cortex. [3H]DE binding to 5-HT1B sites is very slowly dissociable, with a T1/2 of greater than 2 h at 37 degrees C. 5-HT1B antagonists and DE itself yield competition curves at [3H]DE-labeled 5-HT1B sites that are adequately fit assuming a single site in nonlinear regression analysis. Competition by the agonists 5-HT and RU 24969 at 5-HT1B sites are often best described by two site fits. Addition of 100 microM guanylyl 5'-imidodiphosphate appears to convert nearly all 5-HT1B sites to those having low affinity for agonists while having a much smaller effect on the binding of [3H]DE. This suggests that the 5-HT1B site exists in two interconvertable agonist affinity states and is yet another member of the G-protein-linked receptor family. In agreement with previous studies using other radioligands, no 5-HT1B sites can be detected in bovine, porcine or human hippocampus membranes.

Animals↗
PubMed1987

Ascorbic acid prevents nonreceptor "specific" binding of [3H]-5-hydroxytryptamine to bovine cerebral cortex membranes.

[3H]-5-Hydroxytryptamine ([3H]-5-HT) decomposes rapidly when exposed to air in solution at physiological pH if antioxidants are not present. The decomposition products appear to bind to two saturable sites on brain membranes (apparent Kd values = 1-2 and 100-1000 nM). This binding mimics "specific" ligand/receptor binding in that it is inhibited by 10 microM unlabeled 5-HT. This inhibition is not competitive, but rather is due to the prevention of [3H]-5-HT breakdown by excess unlabeled 5-HT. Unlike genuine ligand/receptor binding, the binding of [3H]-5-HT breakdown products is essentially irreversible and does not display a tissue distribution consistent with binding to authentic 5-HT receptors. [3H]-5-HT decomposition can be eliminated by the inclusion of 0.05 to 5 mM ascorbic acid. At these concentrations ascorbic acid is not deleterious to reversible [3H]-5-HT binding. When [3H] 5-HT exposure to air occurs in the presence of brain membranes, the apparent antioxidant activity of brain membranes themselves affords protection against [3H]-5-HT degradation equal to ascorbic acid. This protection is effective below final [3H]-5-HT concentrations of 10 nM. Above 10 nM [3H]-5-HT, addition of ascorbic acid or other antioxidants is necessary to avoid the occurrence of additional low affinity (apparent Kd = 15-2000 nM) binding sites that are specific but nonetheless irreversible. When care is taken to limit [3H]-5-HT oxidation, the only reversible and saturable specific binding sites observed are of the 5-HT1 high affinity (Kd = 1-2 nM) type. Radioligand oxidation artifacts may be involved in previous reports of low affinity (Kd = 15-250 nM) [3H]-5-HT binding sites in brain membrane preparations.

Animals↗
PubMed1987

Modulation of activity of the striatal dopaminergic system during the hibernation cycle.

To evaluate how the activity of a well-established neurotransmitter pathway is modulated by a behavioral state, 3H-spiperone binding sites and dopamine (DA) and DA metabolite concentrations were measured in the striata of ground squirrels in 5 phases of the hibernation cycle. Whereas levels of striatal DA and its deaminated metabolite DOPAC did not change significantly, the concentrations of the O-methylated-deaminated metabolite, homovanillic acid (HVA), decreased in all phases of hibernation relative to euthermia. Striatal 3H-spiperone binding sites declined across the hibernation cycle in parallel with the reduction of HVA concentration; receptor binding affinity was unchanged by arousal state. In conjunction with previously reported findings, these results are consistent with the hypothesis that hibernation is associated with a down-regulation of the postsynaptic D2 receptors secondary to increased extracellular DA concentration and reduced DA degradation.

3,4-Dihydroxyphenylacetic Acid↗
PubMed1986

Empirically derived subclassification of the autistic syndrome.

A method is presented for empirical subclassification of autistic and autisticlike children, based on observations of current behavior. The advantage of the method is that it identifies profiles of co-occurring behaviors and accordingly assigns children to subtypes. The subtypes are more clinically homogeneous than the overall sample of autistic children. Preliminary findings are presented, including an effort to validate the subclasses by suggesting possible relationships between subtype membership and perinatal markers, developmental milestones, and independent measures of concurrent behavior.

Adolescent↗
PubMed1986

Muscarinic cholinergic receptors and the canine model of narcolepsy.

The role of the muscarinic cholinergic receptor in narcolepsy was examined using radioligand binding to various brain regions of normal and genetically narcoleptic Doberman pinschers. In this multi-litter study, a previous report of a proliferation of muscarinic cholinergic receptors in the brainstem was confirmed, and the concentration of the M2 receptor subtype, in particular, was elevated. This up-regulation of brainstem cholinergic receptors suggests a problem with release of acetylcholine, which, together with previous reports of an impairment of dopamine release, may be indicative of a fundamental membrane problem in narcolepsy.

Amygdala↗
PubMed1986

Brain benzodiazepine receptor characteristics in canine narcolepsy.

A regional analysis of brain benzodiazepine (BDZ) receptors was conducted in narcoleptic and normal dogs to determine whether these sites are altered in narcolepsy. It was postulated that BDZ receptors play a role in the excessive sleepiness of narcolepsy because activation of these sites in freely behaving normal animals is hypnogenic. [3H]Flunitrazepam binding sites were assessed in 11 discrete areas of the forebrain and brainstem. No consistent or statistically significant group differences in either receptor densities (Bmax) or binding affinities (Kd) were found. These findings do not support the assertion that BDZ receptors are involved in the pathogenesis of canine narcolepsy.

Animals↗
PubMed1985

Comparison of dopamine beta-hydroxylase activity in normal rat adrenal medulla and rat pheochromocytoma cells.

Dopamine beta-hydroxylase activity is reportedly negligible in malignant rat adrenal cell lines. However, in two pheochromocytoma cell lines, PC12 and PCG2, considerable amounts of this catecholamine enzyme exist but its characteristics differ from the enzyme found in normal rat tissue in two ways. First, in normal adrenal medullary tissue, dopamine beta-hydroxylase activity increases linearly with increasing protein concentration. Second, there is a stringent requirement for copper. Concentrations of copper above or below the optimum inhibit enzymatic activity. In contrast, in pheochromocytoma cells, dopamine beta-hydroxylase exhibits a sigmoidal response with increasing tissue content. At dilute protein concentrations where considerable dopamine beta-hydroxylase activity is observed in normal adrenal medullary extracts, enzymatic activity is negligible in the pheochromocytoma cell lines. As the protein concentration is increased, activation of the enzyme occurs, and enzymatic activity increases linearly with further increases in protein concentration. At very high concentrations of protein, enzymatic activity plateaus. For both PC12 and PCG2 cells, dopamine beta-hydroxylase activity shows minimal copper dependency, suggesting that endogenous inhibitors present in normal tissue are absent in these malignant cell lines. Under conditions of maximum activation, the activity of the enzyme in PC12 cells becomes equivalent to that in normal rat adrenal medulla but remains 45-fold greater than that in PCG2 cells.

Adrenal Gland Neoplasms↗
PubMed1985

Pharmacological characterization of solubilized 5-HT1 serotonin binding sites from bovine brain.

This report describes the pharmacologic characterization of [3H]serotonin binding activity solubilized from bovine frontal cortical membranes. The ability of a number of serotonin (5-HT) and lysergic acid diethylamide (LSD) analogs to compete with [3H]serotonin and D-[3H]LSD for binding to membrane and solubilized 5-HT1 sites has been investigated. The results indicate that the solubilized binding site is probably of the 5-HT1B type. Fifteen of the 21 compounds tested exhibit nearly identical affinity for membrane or solubilized 5-HT1 binding sites. However, some important differences were observed, and these may help elucidate the molecular structure of the binding site. In particular, some N-substituted tryptamine analogs show a markedly lower affinity for solubilized 5-HT1 sites compared to their binding to intact membranes. Further, the solubilized site does not distinguish stereoisomers of LSD: both D- and L-LSD bind to solubilized 5-HT1 sites with comparable high affinities, whereas D-LSD has a markedly higher affinity for the membrane 5-HT1 site. Methiothepin, which binds to the 5-HT1 site primarily through its amine groups, has virtually no affinity for the solubilized receptor, whereas it is quite potent at competing for [3H]serotonin binding to membrane sites. These observations lead to the conclusions that in bovine cortical membranes, the 5-HT1 site contains both indole and amine attachment sites. After solubilization, the indole attachment site retains its binding properties, but the amine attachment site has been significantly altered.(ABSTRACT TRUNCATED AT 250 WORDS)

Amines↗
PubMed1985

Co-localization of substance P- and phenylethanolamine-N-methyltransferase-like immunoreactivity in neurons of ventrolateral medulla that project to the spinal cord: potential role in control of vasomotor tone.

Both substance P (SP)- and epinephrine-containing neurons in the rostral ventrolateral medulla have been thought to play a role in regulating vasomotor tone. The combination of retrograde transport of a fluorescent dye (Fast Blue) and immunofluorescent staining for SP- and phenylethanolamine-N-methyltransferase (PNMT)-immunoreactivity was used to determine the relationships of these two groups of ventrolateral medullary neurons which project to the spinal cord. The majority of spinally projecting neurons in the rostral ventrolateral medulla contain both PNMT-like and SP-like immunoreactivity. The presence of PNMT-immunoreactive material in a neuron implies that epinephrine is a probable neurotransmitter for such a cell. Earlier work demonstrated that epinephrine and SP have opposite effects on the firing of sympathetic preganglionic neurons. Our results raise the possibility of a novel mechanism of synaptic regulation of the sympathetic preganglionic vasomotor neurons.

Animals↗
PubMed1985

Regulation of biogenic amine methyltransferases by glucocorticoids via S-adenosylmethionine and its metabolizing enzymes, methionine adenosyltransferase and S-adenosylhomocysteine hydrolase.

This report examines the possibility that glucocorticoids control the degradation of adrenal phenylethanolamine N-methyltransferase and pineal hydroxyindole O-methyltransferase by regulating endogenous concentrations of the cosubstrate, S-adenosylmethionine, via its metabolic enzymes, methionine adenosyltransferase and S-adenosylhomocysteine hydrolase. Assays for these latter enzymes were established and optimized in the adrenal and pineal glands. The effects of hypophysectomy and dexamethasone or ACTH treatment on these enzymes were monitored along with concomitant changes in methyltransferase activity. Hypophysectomy simultaneously decreases methionine adenosyltransferase and S-adenosylhomocysteine hydrolase activity in both tissues. Dexamethasone administration to hypophysectomized animals does not alter either methionine adenosyltransferase activity or S-adenosylhomocysteine hydrolase activity in the adrenal gland. However, it does increase S-adenosylhomocysteine hydrolase activity in the pineal gland. In contrast, ACTH administration restores both enzymes in the adrenal while being ineffective in the pineal. These results suggest that glucocorticoids may be regulating S-adenosylmethionine levels and methyltransferase activity via the metabolic enzymes, methionine adenosyltransferase and S-adenosylhomocysteine hydrolase, but that glucocorticoid control may be both tissue- and drug-specific.

Acetylserotonin O-Methyltransferase↗
PubMed1985

Central effects of RDS-127: sexual behavior after intracerebroventricular administration and in vitro receptor binding studies.

RDS-127, in a dose-related manner, induced seminal emission ex copula after intracerebroventricular (i.c.v.) administration. In mating tests initiated 6 min after i.c.v. administration, RDS-127 induced decreases in ejaculation latency and intromission frequency, with some rats ejaculating on the initial intromission. Additionally, penile reflexes were eliminated by 150 micrograms and 600 micrograms, but not by an intermediate dose. In in vitro radioligand binding studies, RDS-127 potently displaced [3H]DPAT binding to 5-HT1A sites in rat cortex (Ki = 14 +/- 4 nM) and was only moderately effective in displacing [3H]spiperone binding to dopaminergic D2 sites in rat striatum. RDS-127 was essentially ineffective at 5-HT1B sites labeled by [3H]5-HT in rat striatum (Ki = 13 000 +/- 4 000 nM). These data demonstrate that centrally administered RDS-127 mimics the previously reported alterations in sexual behavior after systemic treatment and that RDS-127 is a high affinity 5-HT1A agent with low affinity at the 5-HT1B binding site.

8-Hydroxy-2-(di-n-propylamino)tetralin↗
PubMed1985

Demonstration of inter- and intraspecies differences in serotonin binding sites by antibodies from an autistic child.

Serotonin (5-HT) binding sites from bovine and rat cerebral cortex membranes share pharmacological properties that allow both to be subclassified by the same criteria. We show here that [3H]5-HT binding sites from human cortex also possess pharmacological properties that follow the same subclassification scheme as for bovine and rat cortex. In addition, we show that solubilized 5-HT1 and 5-HT3 sites from all three species have an s20,w value of 3.4. Despite these similar pharmacological and physical characteristics, we can demonstrate antigenic differences between receptor types and species. Human 5-HT1A sites can be distinguished from human 5-HT1B, 5-HT2, and 5-HT3 sites and from equivalent sites in rat and bovine cortex. The anti-human 5-HT1A antibodies were discovered in the blood of an autistic child and may have clinical or etiologic significance for this disorder.

Animals↗
PubMed1984

Narcolepsy: cholinergic receptor changes in an animal model.

An inbred colony of narcoleptic doberman pinschers has been analyzed for muscarinic receptor levels in 19 discrete brain regions. In comparison to age-matched controls, receptors were generally elevated in the brainstem and reduced in forebrain areas. No changes in receptor binding affinity were detected. The increased receptor levels found in the brainstem suggest that cholinoceptive neurons in this region are hypersensitive and may be involved in the initiation of cataplexy and other aspects of the narcolepsy syndrome.

Animals↗
PubMed1984

alpha-Noradrenergic potentiation of neurotransmitter-stimulated cAMP production in rat striatal slices.

The present study examines the possible involvement of alpha-adrenergic receptors in catecholamine-stimulated cAMP production in intact slices of rat striatum. Norepinephrine (NE) produces a greater stimulation of cAMP levels than does the beta-adrenergic agonist, isoproterenol (ISO), and the NE response is inhibited by both the beta-adrenergic antagonist, propranolol, and the alpha-adrenergic antagonist, phentolamine. The alpha-adrenergic agonist, 6-fluoronorepinephrine (6-FNE), has little or no effect on basal cAMP levels; however, 6-FNE causes a marked potentiation of the cAMP response to ISO. Hence, NE stimulation of cAMP levels in striatal slices appears to involve a synergistic interaction between alpha- and beta-adrenergic receptors. alpha-Receptors also potentiate adenosine stimulation of cAMP levels in striatal slices. However, in contrast to results previously reported in cerebral cortical slices, the alpha-adrenergic component of the NE response in striatal slices is not dependent on endogenous adenosine. Finally, 6-FNE interactions with adenylate cyclase in striatal homogenates differ from those observed in the slice preparation. In homogenates, 6-FNE appears to directly stimulate adenylate cyclase through a D-1 receptor. D-1 receptor involvement in catecholamine responses in the striatal slice preparation, on the other hand, appears to be minimal.

Animals↗
PubMed1983

Narcolepsy: biogenic amine deficits in an animal model.

Concentrations of biogenic amine metabolites in discrete brain areas differed significantly between dogs with genetically transmitted narcolepsy and age- and breed-matched controls. Dopamine and 3,4-dihydroxyphenylacetic acid were consistently elevated in the brains of narcoleptic animals, while homovanillic acid was not. Narcoleptic animals consistently exhibited lower utilization of dopamine and higher intraneuronal degradation of dopamine but no uniform decrease in serotonin utilization. Hence neuropathology appears to be associated with genetically transmitted canine narcolepsy. The data indicate a nonglobal depression of dopamine utilization or turnover or both.

3,4-Dihydroxyphenylacetic Acid↗