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Biomedical subjects

C B Pert

Publications and source records attributed to C B Pert.

At least 91 records · Page 5Linked to original sources
PubMed1985

A quantitative study of [3H]D-Ala2-D-Leu5-enkephalin binding to rat brain membranes. Evidence that oxymorphone is a noncompetitive inhibitor of the lower affinity delta-binding site.

The mechanism by which mu ligands inhibit the binding of prototypic delta agonists to preparations of brain membranes is controversial. Most investigators assume competitive inhibition. In this study, we examine the interaction of the mu agonist oxymorphone and delta agonist DSTLE (D-Ser2-Thr6-Leu-enkephalin) with [3H]D-Ala2-D-Leu5-enkephalin (DADL) binding to membranes of rat brain. According to the two-site competitive model, mu ligands are competitive inhibitors at both sites. The two-site allosteric model supposes that mu ligands are competitive inhibitors at one binding site, and noncompetitive inhibitors at the other binding site. Quantitative analysis of DSTLE and oxymorphone binding demonstrated that the two-site allosteric model fit the data significantly better than did the two-site competitive model, and that oxymorphone is a noncompetitive inhibitor of the lower affinity [3H]DADL-binding site. Autoradiographic studies demonstrated that the lower affinity [3H]DADL-binding site (mu-noncompetitive binding site) had an anatomical distribution apparently indistinguishable from that obtained with [3H]oxymorphone (type I pattern), supporting the hypothesis that the lower affinity delta-binding site is the delta-binding site of an opiate receptor complex consisting of interacting mu- and delta-binding sites.

Animals↗
PubMed1985

Neuropeptides and their receptors: a psychosomatic network.

A major conceptual shift in neuroscience has been wrought by the realization that brain function is modulated by numerous chemicals in addition to classical neurotransmitters. Many of these informational substances are neuropeptides, originally studied in other contexts as hormones, "gut peptides," or growth factors. Their number presently exceeds 50 and most, if not all, alter behavior and mood states, although only endogenous analogs of psychoactive drugs like morphine, Valium, and phencyclidine have been well appreciated in this context. We now realize that their signal specificity resides in receptors (distinct classes of recognition molecules), rather than the close juxtaposition occurring at classical synapses. Rather precise brain distribution patterns for many neuropeptide receptors have been determined. A number of brain loci, many within emotion-mediating brain areas, are enriched with many types of neuropeptide receptors suggesting a convergence of information at these "nodes." Additionally, neuropeptide receptors occur on mobile cells of the immune system; monocytes can chemotax to numerous neuropeptides via processes shown by structure-activity analysis to be mediated by distinct receptors indistinguishable from those found in brain. Neuropeptides and their receptors thus join the brain, glands, and immune system in a network of communication between brain and body, probably representing the biochemical substrate of emotion.

Animals↗
PubMed1985

Nicotinic binding in rat brain: autoradiographic comparison of [3H]acetylcholine, [3H]nicotine, and [125I]-alpha-bungarotoxin.

Three radioligands have been commonly used to label putative nicotinic cholinoceptors in the mammalian central nervous system: the agonists [3H]nicotine and [3H]acetylcholine ([3H]ACh--in the presence of atropine to block muscarinic receptors), and the snake venom extract, [125I]-alpha-bungarotoxin([125I]BTX), which acts as a nicotinic antagonist at the neuromuscular junction. Binding studies employing brain homogenates indicate that the regional distributions of both [3H]nicotine and [3H]ACh differ from that of [125I]BTX. The possible relationship between brain sites bound by [3H]nicotine and [3H]ACh has not been examined directly. We have used the technique of autoradiography to produce detailed maps of [3H]nicotine, [3H]ACh, and [125I]BTX labeling; near-adjacent tissue sections were compared at many levels of the rat brain. The maps of high affinity agonist labeling are strikingly concordant, with highest densities in the interpeduncular nucleus, most thalamic nuclei, superior colliculus, medial habenula, presubiculum, cerebral cortex (layers I and III/IV), and the substantia nigra pars compacta/ventral tegmental area. The pattern of [125I]BTX binding is strikingly different, the only notable overlap with agonist binding being the cerebral cortex (layer I) and superior colliculus. [125I]BTX binding is also dense in the inferior colliculus, cerebral cortex (layer VI), hypothalamus, and hippocampus, but is virtually absent in thalamus. Various lines of evidence suggest that the high affinity agonist-binding sites in brain correspond to nicotinic cholinergic receptors similar to those found at autonomic ganglia; BTX-binding sites may also serve as receptors for nicotine and are possibly related to neuromuscular nicotinic cholinoceptors.

Acetylcholine↗
PubMed1984

Autoradiographic distribution of nicotine receptors in rat brain.

The autoradiographic visualisation of 90%-specific tritiated nicotine binding to slide-mounted sections of rat brain is reported. Tritiated nicotine bound with high affinity (nanomolar Kd) and was selectively displaced by nicotinic agonists (e.g. L-nicotine approximately ACh greater than D-nicotine). The strikingly discrete distribution pattern obtained deviates from that of alpha-bungarotoxin, and suggests several possible roles for nicotinic transmission in the brain.

Alzheimer Disease↗
PubMed1984

3-[18F]Acetylcyclofoxy: a useful probe for the visualization of opiate receptors in living animals.

A fluoro-analogue of the potent narcotic antagonist, naltrexone, was synthesized and shown to bind with high affinity to opiate receptors in vitro. 3-[18F]acetylcyclofoxy was prepared via a one-step triflate displacement reaction with the positron emitting 18F ion from tetraethylammonium [18F] fluoride. 3-[18F]acetylcyclofoxy accumulation in opiate receptor rich brain regions of both rat and baboon is shown to be completely displaced by the active enantiomer of naloxone [-)-naloxone) while the identical dose of the pharmacologically inert (+)-naloxone has no detectable effect. Moreover, both rat and baboon brain showed the well documented, typical opiate receptor distribution so that basal ganglia and thalamus are clearly visible in the living baboon brain up to 95 min after intravenous injection of 3-[18F] acetylcyclofoxy. We expect that 3-[18F )acetylcyclofoxy will be a useful probe for visualizing opiate receptors in living humans.

Animals↗
PubMed1984

Small cell carcinoma of the lung: macrophage-specific antigens suggest hemopoietic stem cell origin.

Four surface antigens previously recognized only in macrophages are present on human small cell lung carcinoma cells and tumors. Cancerous cells may arise from macrophage precursors in bone marrow, and these precursors migrate to lung to participate in the repair of damaged tissue produced by continuous heavy smoking. The characteristic presence of neuropeptides such as bombesin in small cell carcinoma, when considered along with these findings, presents new possibilities for the role of such peptides in nervous, endocrine, and immune system function.

Antigens, Neoplasm↗
PubMed1984

Visualization of rat brain receptors for the neuropeptide, substance P.

Biochemical analysis of the binding of [125I]Bolton-Hunter coupled substance P [( 125I]BH-SP) to slide-mounted sections of rat brain demonstrated that [125I]BH-SP labels a binding site with a structure-activity profile characteristic of a substance P receptor. Under optimized preincubation and incubation conditions, the locations of substance P (SP) receptors were visualized by film and emulsion autoradiography. Receptor densities were quantified by computer-assisted densitometry. SP receptors are widely but discretely distributed throughout sensory, limbic and cortical areas of rat brain, though several motor areas also possess SP receptors. No receptors were detected in the substantia nigra and interpeduncular nucleus, which are innervated by SPergic nerves; these regions of the brain may possess a low affinity SP receptor not detectable with this assay. Findings are discussed in the framework of an overall notion of the role of neuropeptides in the biochemistry of emotion.

Animals↗
PubMed1984

In vivo autoradiography: visualization of stress-induced changes in opiate receptor occupancy in the rat brain.

A method of in vivo autoradiography was utilized which allows the visualization of local changes in opiate receptor occupation in the intact rat brain. The method is based on the exclusion of [3H]diprenorphine binding in areas in which the release of endogenous opiate peptides is increased by behavioral manipulation. The technique lends itself to the use of film autoradiography, allowing the mapping of relative levels of functional receptor occupancy throughout the whole brain. Prolonged intermittent footshock and forced swims in cold water (two stress-inducing manipulations which are known to release endogenous opiates) were found to cause highly significant decreases in specific high-affinity [3H]diprenorphine binding, as measured by liquid scintillation counting. These changes were unaccompanied by corresponding changes in non-specific binding and were not related to local changes in blood flow. A prolonged non-stressful swim in warm water caused no changes in [3H]diprenorphine binding. The use of tritium-sensitive film autoradiography allowed the resolution of these decreases to the level of individual nuclei. Differences in specific binding were found to be greatest in the periaqueductal gray, the reticular formation, and in midline-intralaminar thalamic nuclei, all of which have been implicated in the modulation of pain sensation.

Animals↗
PubMed1984

Tritiated-6-beta-fluoro-6-desoxy-oxymorphone: a highly selective ligand for the opiate mu receptor whose binding is characterized by low nonspecific binding.

In this paper we examine the binding of [3H]FOXY (tritiated-6-beta-fluoro-6-desoxy-oxymorphone) to membranes of rat brain. Using the site-directed alkylating agents BIT and FIT, evidence is presented that [3H]FOXY selectively labels mu opiate binding sites in vitro. Further, BIT and FIT did not significantly affect [3H]bremazocine binding to kappa receptors. Scatchard plots of [3H]FOXY binding were somewhat curvilinear, suggesting the presence of two classes of mu binding sites. At concentrations up to 19 nM, 90 percent of the total binding was specific. The combination of high mu-selectivity and low nonspecific binding suggests the [3H]FOXY may prove to be a powerful tool for studying the opiate mu receptor.

Animals↗
PubMed1984

Autoradiographic localization of a novel peptide binding site in rat brain using the substance P analog, eledoisin.

Using slide mounted sections of rat brain sausage, we have characterized the binding of [125I]Bolton Hunter conjugated eledoisin and [125I]Bolton Hunter conjugated substance P. Structure activity studies suggest that the two radiolabeled peptides bind to different binding sites. Autoradiographic studies support this notion. Whereas [125I]BH-SP sparsely labels the interpeduncular nucleus and does not label the substantia nigra at all, [125I]BH-ED densely labels the former and sparsely labels the latter structure. Further, the cortical labeling patterns obtained with the two peptides are strikingly different. These data support the hypothesis that there exist two classes of tachykinin binding sites in rat nervous tissue.

Animals↗
PubMed1984

Preparation of rat brain membranes greatly enriched with either type-I-delta or type-II-delta opiate binding sites using site directed alkylating agents: evidence for a two-site allosteric model.

Although it is widely accepted that radiolabeled prototypic delta receptor agonists label two binding sites in vitro, the mechanism by which mu ligands inhibit peptide binding as well as the identity of the binding sites remains unsettled (Rothman and Westfall, Mol. Pharmacol. 21:538-547, 1982 ; Bowen et al., Proc. Natl. Acad. Sci. U.S.A. 78:4818-4822, 1981). Using the site directed, receptor selective alkylating agents, BIT and FIT (Rice et al., Science 220:314-316, 1983), we describe the preparation of membranes devoid of high affinity binding sites and demonstrate that the mu agonist oxymorphone noncompetitively inhibits the binding of [3H]DADL to the residual lower affinity binding sites.

Alkylating Agents↗
PubMed1984

Morphine noncompetitively inhibits [3H]leucine enkephalin binding to membranes lacking type-II delta binding sites: evidence for a two-site allosteric model.

Using the site-directed, delta-selective alkylating agent FIT (Rice et al., Science 220, 314-316, 1983), membranes devoid of detectable higher affinity delta binding sites were prepared. As compared to control membranes, the IC50 of morphine required to inhibit [3H]LE binding to FIT-treated membranes was two orders of magnitude lower. Further, morphine was a noncompetitive inhibitor of [3H]LE binding to FIT-treated membranes, supporting the notion that the lower affinity delta binding site is the delta binding site of the opiate receptor complex.

Allosteric Regulation↗
PubMed1984

Ionic conditions differentially affect 3H-DADL binding to type-I and type-II opiate delta receptors in vitro.

It is widely accepted that the prototypic delta agonist DADL (D-ala2-D-leu5-enkephalin) labels two binding sites in vitro. Using the site directed, receptor selective alkylating agents, BIT and FIT (Rice et al.. Science 220:314-316, 1983), we recently described (Rothman et al, Neuropeptides, in press) the preparation of membranes possessing only lower affinity 3H-DADL binding sites (FIT-treated membranes, type-I delta sites) as well as membranes greatly enriched with higher affinity binding sites (BIT-treated membranes, type-II delta sites). In this paper we report that ionic conditions differentially affect the binding of 3H-DADL to FIT- and BIT-treated membranes, supporting the notion that 3-H-DADL labels two distinct delta binding sites.

Animals↗
PubMed1984

Effect of beta-FNA on opiate delta receptor binding.

beta-FNA, the beta-fumaramate methyl ester of naltrexone, has been shown to antagonize irreversibly the actions of morphine on the guinea pig ileum and mouse vas deferens bioassays but does not affect the actions of delta-receptor ligands on the mouse vas deferens bioassay, suggesting that the compound does not irreversibly bind to the delta receptor. In this paper we examine the effect of beta-FNA on the binding of the prototypic delta agonists, Leu-enkephalin and D-Ala2-D-Leu5-enkephalin, its metabolically stable analogue, and show that treatment of membranes with beta-FNA does lead to alterations in the in vitro properties of delta receptors.

Animals↗
PubMed1983

Opiatergic projection from the bed nucleus to the habenula: demonstration by a novel radioimmunohistochemical method.

In a modification of the indirect immunohistochemical method 125I-labeled secondary antibodies were used to autoradiographically visualize enkephalin-like immunoreactivity. Electrolytic lesions of the bed nucleus of the stria terminalis (BNST) resulted in a decrease in enkephalin-like immunoreactivity in the ipsilateral habenula. This suggests an opiatergic pathway originating in the BNST and projecting to the habenula. In addition, the value of the radioimmunohistochemical technique is discussed.

Animals↗
PubMed1983

Opiate receptor localization in rat cerebral cortex.

The differential distributions of [3H]naloxone-labeled and [3H]D-Ala-D-Leu-enkephalin-labeled opiate receptors in rat cerebral cortex were localized autoradiographically and quantified by grain counting and computerized densitometry. In addition, receptor distributions were compared to terminal patterns of thalamocortical projections labeled by axoplasmic transport of [3H]amino acids. Opiate receptors labeled with [3H]naloxone in a mu ligand selectivity pattern show striking laminar heterogeneity and are densest in limbic cortical areas, intermediate in the motor cortex, and fewest in the primary sensory areas. By contrast, opiate receptors labeled with [3H]D-Ala2-D-Leu5-enkephalin in a delta ligand selectivity pattern are much more homogeneously distributed across both regions and laminae within regions. Mu receptors in most cortical areas have density peaks in layers I and VI and each peak shows a density gradient that is sloped within the layer so that the highest densities are at the most superficial and the deepest portions of cortex. In addition, there is an intermediate peak whose laminar position varies depending on the area in which it is found. In rostral agranular cortex, including limbic and motor areas, the [3H]naloxone binding peaks are in layers I, III, and VI. In primary somatosensory cortex, the intermediate peak is in layer Va and in most of remaining homotypical cortex it is in layer IV. Some areas have only bilaminar labeling, in superficial and deep layers; these include portions of the sulcal and retrosplenial cortices. Piriform and entorhinal cortices have dense [3H]naloxone binding only in the deepest layer and show a descending gradient of density toward the superficial layer. The positions of the mu receptor peaks were compared with termination patterns of projections originating in the thalamus. Close correspondence was found between receptor binding in the prelimbic, primary somatosensory, and entorhinal areas and projection terminations arising from the thalamic mediodorsal, posterior, and central medial nuclei, respectively. Although regional variations in [3H]D-Ala2-D-Leu5-enkephalin-labeled receptor density are uncommon, a gradual decrease in the number of sites along the dorsomedial wall of the cortex from anterior cingulate to caudal retrosplenial limbic cortex can be observed. Laminar variations in binding density are small as well; higher concentrations of the peptide binding sites are usually found in the deep cortical layers. These findings emphasize aspects of opiate receptor architecture which may be relevant to identifying cortical "opiatergic" neurocircuitry and raise the possibility of opiate modulation of thalamocortical transmission.

Animals↗