Rosuvastatin enhances anti-inflammatory and inhibits pro-inflammatory functions in cultured microglial cells

Microglial activation results in profound morphological, functional and gene expression changes that affect the pro- and anti-inflammatory mechanisms of these cells. Although statins have beneficial effects on inflammation, they have not been thoroughly investigated for their ability to affect microglial functions. Therefore the effects of rosuvastatin, one of the most commonly prescribed drugs in cardiovascular therapy, either alone or in combination with bacterial lipopolysaccharide (LPS), were profiled in pure microglial cultures derived from the forebrains of 18-day-old rat embryos. To reveal the effects of rosuvastatin on a number of pro- and anti-inflammatory mechanisms, we performed morphometric, functional and gene expression studies relating to cell adhesion and proliferation, phagocytosis, pro- and anti-inflammatory cytokine (IL-1β, tumor necrosis factor α (TNF-α) and IL-10, respectively) production, and the expression of various inflammation-related genes, including those related to the above morphological parameters and cellular functions. We found that microglia could be an important therapeutic target of rosuvastatin. In unchallenged (control) microglia, rosuvastatin inhibited proliferation and cell adhesion, but promoted microspike formation and elevated the expression of certain anti-inflammatory genes (Cxcl1, Ccl5, Mbl2), while phagocytosis or pro- and anti-inflammatory cytokine production were unaffected. Moreover, rosuvastatin markedly inhibited microglial activation in LPS-challenged cells by affecting both their morphology and functions as it inhibited LPS-elicited phagocytosis and inhibited pro-inflammatory cytokine (IL-1β, TNF-α) production, concomitantly increasing the level of IL-10, an anti-inflammatory cytokine. Finally, rosuvastatin beneficially and differentially affected the expression of a number of inflammation-related genes in LPS-challenged cells by inhibiting numerous pro-inflammatory and stimulating several anti-inflammatory genes. Since the microglia could elicit pro-inflammatory responses leading to neurodegeneration, it is important to attenuate such mechanisms and promote anti-inflammatory properties, and develop prophylactic therapies. By beneficially regulating both pro- and anti-inflammatory microglial functions, rosuvastatin may be considered as a prophylactic agent in the prevention of inflammation-related neurological disorders.

Effects of Pyridazinone Herbicides during Chloroplast Development in Detached Barley Leaves II. Effects on Lipid Content, Fatty Acid Composition and Ultrastructure of Chloroplasts

The effects of three differently substituted pyridazinone herbicides were studied on the lipid content, fatty acid composition of glycerolipids, fatty acid synthesizing capacity and ultrastruc­ture of chloroplasts after 72 h of greening of etiolated barley leaves. SAN 9789 caused a nearly threefold increase in the total fatty acid content of chloroplasts. and this increase was accom­panied by an increase in the DGDG- and phospholipid-content as well. SAN 6706 and 9785 caused reduction in the linolenic to linoleic acid ratio in nearly all lipid classes, only PC was unaffected. Both herbicides reduced the saturated to unsaturated ratio in the PG, SAN 9789 had no effect on the fatty acid composition of the PG. Fatty acid synthesis was inhibited in the SAN 6706- and 9789-treated leaves as monitored by incorporation of labelled acetate, but all of the three pyridazinones stimulated the incorporation of labelled galactose into chloroplast galactolipids. SAN 6706 and 9789 also caused abnormal organization of chloroplast lamellar system.

Development of the microglial phenotype in culture

Selected morphological, molecular and functional aspects of various microglial cell populations were characterized in cell cultures established from the forebrains of E18 rat embryos. The mixed primary cortical cultures were maintained for up to 28days using routine culturing techniques when the microglial cells in the culture were not stimulated or immunologically challenged. During culturing, expansion of the microglial cell populations was observed, as evidenced by quantitative assessment of selected monocyte/macrophage/microglial cell-specific markers (human leukocyte antigen (HLA) DP, DQ, DR, CD11b/c and Iba1) via immunocyto- and histochemistry and Western blot analysis. The Iba1 immunoreactivity in Western blots steadily increased about 750-fold, and the number of Iba1-immunoreactive cells rose at least 67-fold between one day in vitro (DIV1) and DIV28. Morphometric analysis on binary (digital) silhouettes of the microglia revealed their evolving morphology during culturing. Microglial cells were mainly ameboid in the early stages of in vitro differentiation, while mixed populations of ameboid and ramified cell morphologies were characteristic of older cultures as the average transformation index (TI) increased from 1.96 (DIV1) to 15.17 (DIV28). Multiple immunofluorescence labeling of selected biomarkers revealed different microglial phenotypes during culturing. For example, while HLA DP, DQ, DR immunoreactivity was present exclusively in ameboid microglia (TI<3) between DIV1 and DIV10, CD11b/c- and Iba1-positive microglial cells were moderately (TI<13) and progressively (TI<81) more ramified, respectively, and always present throughout culturing. Regardless of the age of the cultures, proliferating microglia were Ki67-positive and characterized by low TI values (TI<3). The microglial function was assessed by an in vitro phagocytosis assay. Unstimulated microglia with low TI values were significantly more active in phagocytosing fluorescent microspheres than the ramified forms. In vitro studies on microglial population dynamics combined with phenotypic characterization can be of importance when different in vivo pathophysiological situations are modeled in vitro.

Somato-dendritic synapses in the nucleus reticularis thalami of the rat

In the reticular nucleus of the rat thalamus, about 30% of the synapses are brought about by the perikarya of parvalbumin-immunopositive neurons, which establish somato-dendritic synapses with large dendrites of nerve cells of specific thalamic nuclei. Although the parvalbumin-immunopositive presynaptic structures bear resemblance to goblet-like or calyciform axonal endings, electron microscopic immunocytochemistry and in situ hybridization revealed that these structures are parts of the perikaryal cytoplasm studded with synaptic vesicles. In about 15% of the somato-dendritic synapses, axons are seen to be in synaptic contact with the parvalbumin-immunoreactive perikaryon. Double immunohistochemical staining revealed that the parvalbumin immunoreactive presynaptic perikarya and dendrites contained GABA. It is assumed that the peculiar somato-dendritic synaptic complexes subserve the goal of filtration of impulses arriving at the reticular nucleus from various thalamic nuclei, thus processing them for further sampling.

Branching-pattern analysis of the dendritic arborization in the thalamic nuclei of the rat brain

We investigated the dendritic patterns of rapid Golgi-impregnated, highly similar multipolar neurons from two functionally different thalamic regions of the rat brain: two dorsal nuclei (the nucleus laterodorsalis thalami, pars dorsomedialis and the nucleus laterodorsalis thalami, pars ventrolateralis), and two ventral nuclei (the nucleus ventrolateralis thalami and the nucleus ventromedialis thalami). The analysis involved conventional morphometric parameters (height and size) and a new parameter derived from graph theory, the relative imbalance (RI), derived from the branching patterns of the dendrites, which permits quantitative characterization of the dendritic arborization of a neuron. On this basis, neurons can be grouped into three fundamentally different types: type A, or highly-polarized (imbalanced) neurons (RI values close to 1); type B, or medium-polarized neurons (RI values around 0.5); and type C, or balanced neurons with low polarization (RI values close to 0). The orientations of the dendritic arbor, and thus the receptive fields, of the dorsal and ventral thalamic neurons, were mutually perpendicular. The H and S values indicated that the neurons in the dorsal and ventral thalamic nuclei differed significantly. However, their RI values demonstrated that they were similar neurons of type B. Our data reveal that 1 ) the dendritic arbor cannot be reliably characterized purely on the basis of height and size, and 2) RI is a valuable morphometric parameter that identifies the true nature of the dendritic arborization.

Ontogeny of calmodulin gene expression in rat brain

Calmodulin (CaM), a multifunctional intracellular calcium receptor, is a key element in signaling mechanisms. It is encoded in vertebrates by multiple apparently redundant genes (CaM I, II, III). To investigate whether differential expression takes place in the developing rat brain, a quantitative in situ hybridization analysis was carried out involving 15 brain areas at six ages between embryonic day 19 and postnatal day 20 (PD20) with gene-specific [(35)S]cRNA probes. A widespread, developmental stage-specific and differential expression of the three CaM genes was observed. The characteristic changes in the CaM mRNA levels in the examined time frame allowed the brain regions to be classified into three categories. For the majority of the areas (e.g. the piriform cortex for CaM III), the signal intensities peaked at around PD10 and the expression profile was symmetric (type 1). Other regions (e.g. the cerebral cortex, layer 1 for CaM II) displayed their highest signal intensities at the earliest age measured, followed by a gradual decrease (type 2). The signal intensities in the regions in the third group (e.g. the hypothalamus for CaM III) fluctuated from age to age (type 3). Marked CaM mRNA levels were measured for each transcript corresponding to the three CaM genes in the molecular layers of the cerebral and cerebellar cortici and hippocampus, suggesting their dendritic translocation. The highest signal intensity was measured for CaM II mRNA, followed by those for CaM III and CaM I mRNAs on PD1. However, the CaM II and CaM III mRNAs subsequently decreased steeply, while the CaM I mRNAs were readily detected even on PD20. Our results suggest that during development (1) the transcription of the CaM genes is under differential, area-specific control, and (2) a large population of CaM mRNAs is targeted to the dendritic compartment in a gene-specific manner.

Methods for quantification of in situ hybridization signals obtained by film autoradiography and phosphorimaging applied for estimation of regional levels of calmodulin mRNA classes in the rat brain

Comparative analysis of the regional abundances of the various mRNAs in neural tissues requires the quantitation of target nucleic acid sequences while their tissue distribution is preserved. A quantitative in situ hybridization protocol is presented for the assessment of regional levels of calmodulin (CaM) I, II and III mRNAs in the rat brain. Coronal brain cryostat sections were hybridized with multiple CaM [35S]cRNA probes and co-exposed to an autoradiographic film or storage phosphor screen, together with a membrane-based radioactive standard scale. The membrane scale was calibrated against a brain paste standard scale. Regression analyses of the sensitometric graphs of standard scales corresponding to the autoradiographic film and to the storage phosphor screen were performed by means of exponential (ROD=p(1)(1-exp[-p(2)x])) and linear (LI=ax) functions, respectively (ROD is relative optical density, LI is labeling intensity, and x is radioactivity). The ROD/LI values for the hybridized brain regions were converted into cRNA probe copy numbers (estimations of mRNA copy numbers) through use of the above standard scales. This method was applied to compare the regional abundances of multiple CaM mRNAs in the brains of control, dehydrated, chronic ethanol-treated and ethanol withdrawal-treated animals.

Postischemic calmodulin gene expression in the rat hippocampus

The hippocampal calmodulin (CaM) gene expression was determined in the rat after transient forebrain ischemia. Ischemia was induced by the 4-vessel occlusion model, and the hybridized mRNA copy numbers corresponding to the 3 CaM genes detected by phosphorimaging were determined by quantitative in situ hybridization 24 h post-insult. A small, but significant upregulation (by 8.8%) of the CaM I gene was observed in the CA1 pyramidal cell layer, whereas other regions exhibited a maintained or slightly decreased CaM gene expression. The CaM mRNA levels decreased most markedly (by 10-15%) in the hippocampal molecular layers. No consistent correlation was found between the ischemic vulnerability and the CaM gene expression pattern. The results indicate that the induction of delayed neuronal death is not incidental to the transcriptional activation of the CaM genes in the ischemic rat hippocampus in vivo. As the calcium-bound CaM content increases during the ischemic insult, downregulation of the CaM gene expression could be a homeostatic response aimed at maintaining the intracellular level of the active CaM pool.

Multiple calmodulin genes exhibit systematically differential responses to chronic ethanol treatment and withdrawal in several regions of the rat brain

Ethanol induces profound alterations in the neuronal signaling systems, including the calcium (Ca(2+)) signaling. Prolonged exposure to ethanol evokes adaptive changes in the affected systems as they strive to restore the normal neuronal function. We investigated the involvement of calmodulin (CaM) genes, coding for the major mediator protein of intracellular Ca(2+) signals, in these adaptive processes at the mRNA level. The changes induced in the regional abundances of the CaM I, II, and III mRNA classes by chronic ethanol treatment and withdrawal were examined by means of quantitative in situ hybridization, employing gene-specific [35S]cRNA probes on rat brain cryostat sections. Regional analysis of the resulting changes in mRNA levels highlighted brain areas that belong in neuronal systems known to be especially sensitive to the action of ethanol. The results revealed systematically differential regulation for the three mRNA classes: the CaM I and CaM III mRNA levels displayed increases, and CaM II levels decreases in the affected brain regions, in both chronic ethanol- and withdrawal-treated animals. As regards the numbers of brain regions undergoing significant alterations in mRNA content, the CaM I mRNA levels exhibited changes in most brain areas, the CaM II levels did so in a lower number of brain regions, and the CaM III levels changed in only a few brain areas. These results suggest a differential regulation for the CaM genes in the rat brain and may help towards elucidation of the functional significance of the multiple CaM genes in the mammalian genome.

Calmodulin gene expression in an immortalized striatal gabaergic cell line

We have demonstrated the presence of the mRNAs transcribed from the three calmodulin (CaM) genes in the GABAergic cell line M26-1F derived from embryonic rat striatal cells and immortalized by oncogene transduction. Similarly as in the rat striatum in vivo, these clonal cells express CaM I, CaM II and CaM III mRNAs differently, the CaM I mRNA population being the most abundant, followed in sequence by the CaM II and CaM III mRNA populations. The proportions of these transcripts resemble those in the adult striatum. The possibility of deriving immortalized cell lines from primary neuronal tissue which exhibit characteristics similar to those of the tissue of origin could provide an important tool in many types of in vitro studies.

beta-Amyloid[1-40]-induced early hyperpolarization in M26-1F cells, an immortalized rat striatal cell line

The short-term (20-minute) action of beta[1-40]-amyloid on the resting transmembrane potential was investigated by means of flow-cytofluorimetric studies in M26-1F cells, an immortalized rat striatal cell line, using the potential-sensitive fluorescent probe bis-oxonol. The distribution of the individual cell-associated probe fluorescence was found to be shifted to lower levels in cells treated with beta-amyloid[1-40] for 20 minutes as compared with that of their untreated counterparts. A change in the same direction was caused by valinomycin, a hyperpolarizing ionophore, whereas gramicidin, a depolarizing ionophore, induced a shift to higher fluorescence intensities. These findings, together with the reported behaviour of this particular fluorescent probe at different transmembrane potential levels, indicate that beta-amyloid[1-40] is capable of inducing early hyperpolarization in M26-1F cells. This is one of the earliest cell physiological effect of beta-amyloid peptides that has been reported so far. Moreover, our findings indicate an ionophore-like action of amyloid peptides.

Calculation of maximal hybridization capacity (Hmax) for quantitative in situ hybridization: a case study for multiple calmodulin mRNAs

In estimations of mRNA copy numbers, quantitative in situ hybridization (ISH) is expected to be performed at saturating probe concentration. In practice, however, this condition can rarely be fulfilled when medium to high amounts of transcripts exist and/or in large-scale experiments. To resolve this problem, we developed and tested a double-step procedure involving the use of calmodulin (CaM) I, II, and III [(35)S]-cRNA probes on adult rat brain sections; the hybridization signals were detected with a phosphorimager. By means of hybridization at increasing probe concentrations for a time sufficient for saturation, saturation curves were created for and maximal hybridization capacity (Hmax) values were assigned to selected brain areas. The Kd values of these various brain areas did not differ significantly, which allowed the creation and use of one calibration graph of Hmax vs hybridized [(35)S]-cRNA values for all brain areas for a given probe concentration. Large-scale ISH experiments involving a subsaturating probe concentration were performed to estimate Hmax values for multiple CaM mRNAs. A calibration graph corresponding to this probe concentration was created and Hmax values (expressed in ISH copy no/mm(2) units) were calculated for several brain regions via the calibration. The value of the method was demonstrated by simultaneous quantification of the total accessible multiple CaM mRNA contents of several brain areas in a precise and economical way.

Water deprivation upregulates the three calmodulin genes in exclusively the supraoptic nucleus of the rat brain

Calmodulin (CaM), the ubiquitous intracellular calcium-binding protein, is coded by three bona fide CaM genes (CaM I, CaM II and CaM III) in mammals. They code for the same protein and are transcribed at particularly high levels in the brain, where CaM plays an essential role in basic neuronal functions. In this study, the expression of the three CaM genes in response to osmotic stimuli by water deprivation was investigated in the rat brain, with particular interest as concerns the hypothalamic magnocellular nuclei. CaM mRNA levels were determined by quantitative in situ hybridization autoradiography with gene-specific [35S]cRNA probes. In response to osmotic challenge, it was found that upregulation of the three CaM genes participates in the activation of the hypothalamo-hypophyseal system in the supraoptic nucleus (SON) (126% to 169%), but not in the magnocellular part of the paraventricular hypothalamic nucleus (PVN) (-10%). CaM mRNA levels decreased by 10%-15% in the suprachiasmatic nucleus (SCh) and many other extrahypothalamic brain areas. The opposite responses of the CaM gene expression in the SON and the magnocellular part of the PVN suggest a functional difference between them. Moreover, the significantly different magnitudes of the changes in the CaM mRNA levels in the SON nucleus (138%, 126% and 169% for CaM I, CaM II and CaM III, respectively) exemplify the precise differential control of the CaM gene expression in the brain.

Differential regulation of vasopressin gene expression in the hypothalamus of endotoxin-treated 14-day-old rat

The E. coli endotoxin 0111 B4, a lipopolysaccharide (LPS), in a dose of 200 ng/kg body weight/50 microl artificial cerebrospinal fluid (CSF) was given intracisternally to 14-day-old rats. Four hours later CSF, blood and urine were sampled, and consecutive brain sections from the hypothalamic area of the brain were prepared for in situ hybridization. The LPS treatment resulted in a significant (p<0.001) pleocytosis and an elevation of the protein content of the CSF. There were no changes observed in the chemical parameters of the CSF, plasma, blood or urine, i.e. vasopressin (VP) levels, osmolality, Na+ and K+ concentrations, glucose level, pH, bicarbonate or PaCO2, PaO2 values. LPS injection, however, resulted in a significantly (p<0.01) increased VP mRNA level (121% of the control value) in the supraoptic nuclei (SON), but not in the paraventricular nuclei (PVN), as compared to controls. Our findings suggest an early effect of LPS on VP gene expression selectively in the SON of 14-days-old rats. This animal model might be suitable for studying the regulation of VP gene expression and the role of this peptide in the pathogenesis of bacterial meningitis in pediatric patients.

Differential distribution and intracellular targeting of mRNAs corresponding to the three calmodulin genes in rat brain. A quantitative in situ hybridization study

To investigate the pattern of expression of the three calmodulin (CaM) genes by in situ hybridization, gene-specific [35S]-cRNA probes complementary to the multiple CaM mRNAs were hybridized in rat brain sections and subsequently detected by quantitative film or high-resolution nuclear emulsion autoradiography. A widespread and differential area-specific distribution of the CaM mRNAs was detected. The expression patterns corresponding to the three CaM genes differed most considerably in the olfactory bulb, the cerebral and cerebellar cortices, the diagonal band, the suprachiasmatic and medial habenular nuclei, and the hippocampus. Moreover, the significantly higher CaM I and CaM III mRNA copy numbers than that of CaM II in the molecular layers of certain brain areas revealed a differential dendritic targeting of these mRNAs. The results indicate a differential pattern of distribution of the multiple CaM mRNAs at two levels of cellular organization in the brain: (a) region-specific expression and (b) specific intracellular targeting. A precise and gene-specific regulation of synthesis and distribution of CaM mRNAs therefore exists under physiological conditions in the rat brain.

Slide-binding characterization and autoradiographic localization of delta opioid receptors in rat and mouse brains with the tetrapeptide antagonist [3H]TIPP

Slide-binding and autoradiographic studies were performed on cryostat sections from brains of adult Sprague-Dawley rats and BALB C mice to describe the binding characteristics of the tetrapeptide [3H]TIPP, an antagonist with high specificity and affinity for the delta opioid receptors. Steady-state binding of [3H]TIPP to cryostat sections of brain paste was reached in 120-180 min of incubation. Specific [3H]TIPP binding resulted in maximal numbers of binding sites (Bmax) of 15.59 and 23.91 fmol/mg protein, and dissociation constants (Kd) of 0.46 and 0.85 nM for rat and mouse brain paste sections, respectively. TIPP displayed the highest affinity for delta opioid receptors in inhibiting specific [3H]TIPP binding, with IC50 values of 0.82 nM and 0.14 nM in rat and mouse brain sections, respectively. While DPDPE was also effective in displacing the specific binding of [3H]TIPP (IC50 = 3.18 +/- 0.53 nM and 0.63 +/- 0.42 nM in rat and mouse brain paste sections, respectively), other subclass-selective or nonopioid ligands were much less effective, or ineffective. Autoradiographic localization of [3H]TIPP binding revealed the characteristic distribution of delta opioid receptors in both species. In consequence of its antagonistic nature, and of its unnatural amino acid residue, which makes this ligand more resistant to biodegradation, [3H]TIPP is a superior ligand for evaluation of the binding characteristics and autoradiogaphic distribution of the delta opioid receptors.

A new quantitative film autoradiographic method of quantifying mRNA transcripts for in situ hybridization

We developed and tested a novel quantitative method for the quantification of film autoradiographs, involving a mathematical model and a dot-blot-based membrane standard scale. The exponential model introduced here, ROD = p1(1 - exp[p2x]), appropriately (r2>0. 999), describes the relation between relative optical density (ROD) and radioactivity (x) in the range between 0 and 240 gray scale values (using a 256-gray scale level digitizer). By means of this model, standard curves with distinct quenching properties can be exactly interconverted, permitting the tissue-equivalent calibration of different standard scales. The membrane standard scale employed here has several advantages, including the flexible radioactivity range, the facile and rapid preparation technique, and the compact size. The feasibility of the quantification procedure is exemplified by the comparative quantification of multiple calmodulin mRNAs in the rat brain by in situ hybridization with [35S]-cRNA probes. The procedure for quantification provides a significant improvement in that the direct and exact comparison of radiolabeled species, even from different experiments, can be reliably performed. Further, the procedure can be adapted to the quantification of autoradiographs produced by other methods.

Beta-amyloid(Phe(SO3H)24)25-35 in rat nucleus basalis induces behavioral dysfunctions, impairs learning and memory and disrupts cortical cholinergic innervation

Long-term behavioral effects, changes in learning and memory functions and aberrations of cholinergic fibers projecting to the parietal cortex were investigated after bilateral injections of beta-amyloid(Phe(SO3H)24)25-35 peptide in rat nucleus basalis magnocellularis (nbm). The beta-amyloid peptide used in these experiments contained the original beta-amyloid 25-35 sequence which was coupled to a phenylalanine-sulphonate group at position 24. This additional residue serves as a protective cap on the molecule without influencing its neurotoxic properties and results in water-solubility, stability and low rates of peptide metabolism. In this paper, home cage, locomotor and open-field activities, passive shock-avoidance and 'Morris' water maze learning abilities were assessed throughout a 35-day survival period. Subsequently, acetylcholinesterase (AChE) histochemistry was used to visualize alterations of parietal cortical cholinergic innervation. In response to the neurotoxic action of beta-amyloid(Phe(SO3H)24)25-35, a progressive hyperactivity developed in the rats in their home cages which were maintained throughout the 5-week post-injection period. This was accompanied by a significant hypoactivity in the novel environment of a locomotor arena. Beta-amyloid(Phe(SO3H)24)25-35-treated animals showed greatly impaired cortical memory functions in the step-through passive shock-avoidance paradigm, while spatial learning processes remained unaffected. Moreover, beta-amyloid(Phe(SO3H)24)25-35 injections in the nucleus basalis suppressed explorative behavior in rats and inhibited conditioned stress responses 28 days after surgery. Reductions of cortical cholinergic (AChE-positive) projections provided anatomical substrate for the behavioral changes. This indicated extensive, long-lasting neurodegenerative processes as a result of beta-amyloid(Phe(SO3H)24)25-35 infusion.

The cholinergic system in Alzheimer's disease

The past decade has witnessed an enormous increase in our knowledge of the variety and complexity of neuropathological and neurochemical changes in Alzheimer's disease. Although the disease is characterized by multiple deficits of neurotransmitters in the brain, this overview emphasizes the structural and neurochemical localization of the elements of the acetylcholine system (choline acetyltransferase, acetylcholinesterase, and muscarinic and nicotinic acetylcholine receptors) in the non-demented brain and in Alzheimer's disease brain samples. The results demonstrate a great variation in the distribution of acetylcholinesterase, choline acetyltransferase, and the nicotinic and muscarinic acetylcholine receptors in the different brain areas, nuclei and subnuclei. When stratification is present in certain brain regions (olfactory bulb, cortex, hippocampus, etc.), differences can be detected as regards the laminar distribution of the elements of the acetylcholine system. Alzheimer's disease involves a substantial loss of the elements of the cholinergic system. There is evidence that the most affected areas include the cortex, the entorhinal area, the hippocampus, the ventral striatum and the basal part of the forebrain. Other brain areas are less affected. The fact that the acetylcholine system, which plays a significant role in the memory function, is seriously impaired in Alzheimer's disease has accelerated work on the development of new drugs for treatment of the disease of the 20th century.

Retinopathy induced in mice by targeted disruption of the rhodopsin gene

Retinitis pigmentosa (RP) represents the most common mendelian degenerative retinopathy of man, involving death of rod photoreceptors, cone cell degeneration, retinal vessel attenuation and pigmentary deposits. The patient experiences night blindness, usually followed by progressive loss of visual field. Genetic linkage between an autosomal dominant RP locus and rhodopsin, the photoreactive pigment of the rod cells, led to the identification of mutations within the rhodopsin gene in both dominant and recessive forms of RP. To better understand the functional and structural role of rhodopsin in the normal retina and in the pathogenesis of retinal disease, we generated mice carrying a targeted disruption of the rhodopsin gene. Rho-/- mice do not elaborate rod outer segments, losing their photoreceptors over 3 months. There is no rod ERG response in 8-week-old animals. Rho+/- animals retain the majority of their photoreceptors although the inner and outer segments of these cells display some structural disorganization, the outer segments becoming shorter in older mice. These animals should provide a useful genetic background on which to express other mutant opsin transgenes, as well as a model to assess the therapeutic potential of re-introducing functional rhodopsin genes into degenerating retinal tissues.

Chronic aluminum treatment results in aluminum deposits and affects Ml muscarinic receptors in rat brain

The effects of chronic aluminum (Al) administration on the deposition of the metal and on the receptor binding characteristics of the Ml muscarinic acetylcholine receptors (MlAChR) were studied in selected rat brain areas. Animals were injected intraperitoneally with an AlCl3 solution of 1.0 mg/ml/100 g of body weight for 5 weeks, 5 days a week. Al accumulation was detected by solochrome azurine histochemistry in the brain, where the metal could be visualized in capillaries, endothelial cells and surrounding brain tissues. Changes in the binding properties of the MlAChR after chronic Al treatment were determined with the use of selective and nonselective muscarinic antagonists. Significantly decreased number of maximal MlAChR binding sites (Bmax) as measured by the equilibrium binding of [3H]pirenzepine, were detected in all of the brain areas examined. While the nonselective antagonist [3H] (-)QNB displayed a generally decreased Bmax, value, it reached the level of significance only in the striatum. These results provide a further indication that chronic Al treatment results in the accumulation of Al in the brain and consequently affects the cholinergic neurotransmission.

Beta-amyloid (1-42) affects cholinergic but not parvalbumin-containing neurons in the septal complex of the rat

beta-Amyloid(1-42) peptide (beta AP(1-42) was injected into the medial septum of rats. After a 14-day survival time, neuronal alterations in the septal cholinergic and GABAergic systems were visualized by means of histo- and immunocytochemical methods. Neurons insulted by the peptide were primary choline acetyltransferase-immunoreactive (ir), while only minor effects of beta AP(1-42) were observed on parvalbumin-ir interneurons. These results indicate that the changes in intracellular Ca2+ level elicited by beta AP(1-42) may contribute to beta-amyloid neurotoxicity, and Ca(2+)-binding proteins may play an important role in the protection against the neurotoxic effects of beta AP(1-42).

Cholinotoxic effects of beta-amyloid (1-42) peptide on cortical projections of the rat nucleus basalis magnocellularis

Beta-amyloid(1-42) peptide (betaAP) was injected into the right nucleus basalis magnocellularis (nbm) of rats. After a 14-day survival time, the acetylcholinesterase and choline acetyltransferase activities and the number of muscarinic receptors were found biochemically to be significantly reduced in the ipsilateral frontal cortices. Confirmation of these data with silver staining also revealed degeneration of the projective fibers of the nbm to the frontal cortex. These results demonstrate the cholinotoxicity of betaAP in an in vivo animal model.

[D-Pen2,D-Pen5]enkephalin, a delta opioid agonist reduces endogenous aluminum content in the rat central nervous system

The in vivo effects of [D-Pen2,D-Pen5]enkephalin, a cyclic peptide agonist with high affinity and selectivity for the delta opioid receptors, on the endogenous aluminum content of selected areas of rat brain and spinal cord were studied by means of atomic absorption spectrophotometry. Intracerebroventricular injection of a subanalgesic dose of [D-Pen2,D-Pen5]enkephalin (0.2 microgram/3 microliters) produced a transient, time-dependent reduction of the aluminum content. This effect was statistically significant in the frontal cortex, hippocampus and striatum, but did not reach the level of significance in the medulla and thoracic spinal cord. The partial depleting effect of [D-Pen2,D-Pen5]enkephalin on aluminum content, in the range of 0.2-1.0 micrograms/3 microliters, was dose-dependent and could be reversed by naloxone pretreatment. Serum aluminum levels were unchanged after [D-Pen2,D-Pen5]enkephalin treatment. Chronic (five weeks), systemic AlCl3 treatment increased the endogenous aluminum content in all central nervous system areas examined. Interestingly, [D-Pen2,D-Pen5]enkephalin i.c.v. produced a slight depletion of this elevated metal level in these areas to values not significantly different from those of the respective control values. Chronic in vivo, as well as in vitro, effects of aluminum on opioid receptor binding characteristics were also studied. Neither the specific binding of [3H][D-Pen2,D-Pen5]enkephalin nor [3H]Tyr-D-Ala-Gly-NMePhe-Gly-ol to membranes of frontal or parietal cortices, striatum or hippocampus, prepared from rats chronically treated with AlCl3, were affected.(ABSTRACT TRUNCATED AT 250 WORDS)

Prodynorphin and vasopressin mRNA levels are differentially affected by chronic ethanol ingestion in the mouse

Opioid peptides derived from the precursor, prodynorphin, are co-localized with vasopressin in the hypothalamus and posterior pituitary, and vasopressin and prodynorphin synthesis are coordinately regulated during salt-loading. We had previously found that chronic ethanol ingestion resulted in decreased levels of hypothalamic and extrahypothalamic vasopressin mRNA, and the current study investigated the effect of ethanol ingestion on prodynorphin mRNA levels. A cRNA probe was constructed from a PCR product amplified from mouse genomic DNA. Cloning and sequencing of the PCR product revealed that the sequence of the mouse prodynorphin gene used to synthesize the probe is highly conserved, with high sequence similarity to corresponding regions of the gene in other mammalian species. In situ hybridization using the cRNA probe showed a widespread distribution of prodynorphin mRNA in mouse brain. In dehydrated mice, prodynorphin mRNA was significantly increased in the hypothalamus and nearly all other brain areas examined. In ethanol-fed mice, prodynorphin mRNA was also significantly increased in hypothalamus (50-60%) and in most brain areas. In the same mice, measurement of hypothalamic vasopressin mRNA confirmed a significant (approximately 60%) decrease. These results indicate that hypothalamic vasopressin and prodynorphin mRNA can be differentially regulated in certain situations.

Chronic ethanol ingestion decreases vasopressin mRNA in hypothalamic and extrahypothalamic nuclei of mouse brain

Endogenous arginine vasopressin was previously shown to modulate the rate of loss of functional (CNS) tolerance to ethanol, suggesting that chronic ethanol ingestion might alter vasopressin synthesis and/or release. Since extrahypothalamic vasopressin is believed to be involved in the CNS effects of the peptide, we determined the effect of ethanol on vasopressin mRNA in the bed nucleus of the stria terminalis (BST), as well as in several hypothalamic nuclei. Chronic ethanol ingestion, that produced functional tolerance and physical dependence in mice, resulted in decreased vasopressin mRNA levels in all areas examined. In contrast, as expected, dehydration resulted in increases in vasopressin mRNA in the BST and in all hypothalamic nuclei except the suprachiasmatic nucleus. In the BST, both ethanol ingestion and dehydration affected cells in the central region of the nucleus, while cells in the caudal portion were only affected by ethanol treatment. The results indicate that chronic ethanol ingestion generally reduces the synthesis of vasopressin, and that increased vasopressin synthesis is not necessary in order for the peptide to affect ethanol tolerance.

Regulation of endogenous calcium and magnesium levels by delta opioid receptors in the rat brain

The effects of the potent agonist (D-Pen2, D-Pen5) enkephalin (DPDPE), a conformationally restricted ligand which is highly selective for delta opioid receptors, were studied on the endogenous levels and regional distributions of selected mono- and divalent cations in rat brain and thoracic spinal cord by means of atomic absorption spectrophotometry. In general, lower Na+, K+, Ca2+, Mg2+ and Mn2+ levels were characteristic of the medulla and spinal cord compared to that of cortices, striatum and hippocampus, while the highest metal ion levels were detected in the olfactory bulb. Sixty minutes after a single dose of 0.2 microgram DPDPE, administered intracerebroventricularly, transient decreases of endogenous Ca2+ and Mg2+ contents in the parietal cortex, hippocampus and striatum were found with no changes observed in the levels of monovalent cations or Mn2+. A time-dependent down-regulation in Ca2+ and Mg2+ content was also demonstrated, with Ca2+ being faster to respond to DPDPE treatment. The action of DPDPE was dose-dependent (0.2-1.0 micrograms) and could be antagonized by a 30 min naloxone pretreatment. Naloxone alone had no effect on the endogenous cation levels. It is concluded that delta opioid receptors may specifically be involved in the regulation of endogenous ion levels and their movements in the central nervous system of rat.

Brain regional specificity and time-course of changes in the NMDA receptor-ionophore complex during ethanol withdrawal

Previous work, using membrane receptor binding techniques, demonstrated an increase in hippocampal MK-801 binding sites in mice after chronic ethanol ingestion. The current studies, using quantitative autoradiography, demonstrate that chronic ethanol ingestion also produces increases in MK-801 binding in cerebral cortex, striatum and thalamus, as well as in hippocampus. The persistence of changes in MK-801 binding paralleled the time-course for ethanol withdrawal seizure susceptibility. These results support the hypothesis that an increase in the number of NMDA receptor/channel complexes in hippocampus, and possibly other brain regions, plays a role in the generation or expression of ethanol withdrawal seizures.

Partial depletion of endogenous zinc level by (D-Pen2, D-Pen5)enkephalin in the rat brain

The effects of the potent delta opioid agonist (D-Pen2, D-Pen5)enkephalin (DPDPE) were studied on the endogenous levels and regional distribution of Zn2+ in rat central nervous system by means of flame atomic absorption spectrophotometry. The olfactory bulb exhibited the highest Zn2+ level, followed by the frontal and parietal cortices, striatum and hippocampus; the lowest ion levels were found in the medulla and thoracic spinal cord. Intracerebroventricular administration of DPDPE resulted in significant, time- and dose-dependent decreases in endogenous Zn2+ contents in the parietal cortex, hippocampus and striatum. The action of DPDPE was antagonized by a 30 min naloxone pretreatment. Naloxone alone was without effect in eliciting these responses. Thus, delta opioid receptors may regulate or modulate endogenous Zn2+ levels in the rat brain.

Cholinotoxic effects of aluminum in rat brain

The in vivo and in vitro effects of Al on the cholinergic system of rat brain were studied. The amount of Al accumulated after the chronic, intraperitoneal administration of aluminium gluconate (Al-G) or AlCl3, both at a dose of 1 mg/ml/100 g of body weight, increased in the frontal and parietal cortices, the hippocampus, and the striatum. Significantly decreased choline acetyltransferase activities after chronic Al treatment were measured in the parietal cortex, the hippocampus, and the striatum, but not in the frontal cortex. The acetylcholinesterase activity was not changed significantly in any brain area investigated. Both Al-G and AlCl3 administrations resulted in a general decrease (to 40-70% of the control values) in the specific l-[3H]nicotine binding, involving all brain areas studied. The specific (-)-[3H]quinuclidinyl benzilate binding was reduced (to 40-60% of the control values) only after 25 days of Al treatment. Al-G and AlCl3 were equivalent in eliciting these reductions in vitro studies revealed different alterations of the cholinergic system in response to Al treatment. No changes were observed either in choline acetyltransferase activity or in cholinergic receptor bindings. Both Al-G and Al2(SO4)3 treatments, however, exhibited a biphasic effect on the acetylcholinesterase activity. At low Al concentrations (10(-8)-10(-6) M), the activity was slightly increased, whereas at higher concentrations (10(-6)-10(-4) M), it was inhibited by a maximum of 25% as compared to the controls. Thus, these cholinotoxic effects are probably due not to a direct interaction between the metal and the cholinergic marker proteins, but rather to a manifestation and consequence of its neurodegenerative effects.

Effects of ischemia on cholinergic neurotransmission and electrolyte content in newborn pig lumbar spinal cord

The biochemical changes of the elements of cholinergic neurotransmission (choline acetyltransferase, ChAT; acetylcholinesterase, AChE; butyrylcholinesterase, BuChE; and muscarinic cholinergic receptors, mAChR) as well as the electrolyte content were studied in ischemic lumbar spinal cord segments of newborn pigs. Ischemia was elicited by ligating the aorta for 30 min. Although no significant changes were observed in the sodium, potassium and calcium content of ischemic spinal cords, the calcium content was slightly elevated, to 119.3% of the control value. Whereas significant depletions were observed in both AChE and ChAT activities (to 69.1 and 87.7% of the control value, respectively), there was no significant change in BuChE activity as compared to the control value. The mAChR were also decreased, from 33.25 +/- 2.2 to 27.18 +/- 1.9 fmol/mg protein, while the Kd value was not significantly altered. It is concluded that even a relatively brief interruption of the oxygen supply can cause severe damage in the lumbar spinal cord of the newborn pig, affecting the cholinergic neurotransmission elements. This animal model might be suitable for studying the effects of hypoxia in newborns and children during chest operations involving the descending aorta.

The opioid system in neurologic and psychiatric disorders and in their experimental models

Evidence from experimental and clinical studies suggests the involvement of the endogenous opioid system in several neurologic and psychiatric disorders (Alzheimer's, Huntington's and Parkinson's diseases, drug-induced movement disorders, Gilles de la Tourette syndrome, stroke, ischemia, brain and spinal cord injury, epilepsy, schizophrenia and affective disorders). However, its involvement is rather a secondary one, perhaps being a severe consequence of a primary, nonopioid disturbance. Thus, treatment of an opioidergic manifestation of a disorder of nonopioidergic origin is necessarily symptomatic and targets only the restoration of the opioid system; such treatment may be beneficial in ameliorating the clinical symptoms of the disorder.

The role of arginine vasopressin in alcohol tolerance

Administration of the neuropeptide, arginine vasopressin, to animals that have acquired functional tolerance to ethanol will maintain such tolerance, even in the absence of further ethanol ingestion by the animals. In mice, this action of the peptide is mediated by central nervous system V1 receptors and requires intact brain noradrenergic systems. Autoradiographic studies have shown that some V1 receptors are localized presynaptically on catecholaminergic neuronal terminals in the mouse lateral septum, suggesting that vasopressin may act via modulation of catecholamine release. In addition, vasopressin has been found to increase mRNA levels for the proto-oncogene, c-fos, in septum and hippocampus, possibly by an action at postsynaptic receptors. Expression of c-fos, which has been hypothesized to play a role in central nervous system neuroadaptation, could transform short-term actions of vasopressin into long-term effects on ethanol tolerance. Studies with vasopressin antagonists indicate that the endogenous peptide influences tolerance, and therefore the effect of chronic ethanol ingestion on vasopressin synthesis and release was studied. In mice and rats, hypothalamic vasopressin mRNA is decreased by chronic ethanol exposure, although effects on plasma vasopressin levels differ in the two species. The effect of ethanol on extrahypothalamic vasopressin synthesis in brain is under investigation. The results suggest mechanisms by which vasopressin can produce long-term changes in central nervous system function, and provide evidence for a disturbance of vasopressin regulation during chronic ethanol ingestion.

Transport of muscarinic cholinergic marker protein activities in regenerating sciatic nerve of rat

The transport characteristics of choline acetyltransferase (ChAT; EC 2.3.1.6), acetylcholinesterase (AChE; EC 3.1.1.7), and the muscarinic acetylcholine receptors (mAChR) were studied in perineurally sutured, regenerating rat sciatic nerve. At different times after repair, the sciatic nerve was ligated for 24 h, and the activities of the cholinergic marker proteins, as well as the binding capacity, were measured proximally and distally from the ligature. The number of bidirectionally transported receptors increased linearly up to 5 months postoperatively (6.1-33.6% and 5.6-25.6% of the control level proximal and distal to the ligature, respectively). The quantity of anterogradely transported ChAT reached a plateau 3 months postoperatively (74.9% of the control level), whereas the retrogradely transported enzyme was then only 34.7% of the control value. The activity of AChE increased linearly during nerve regeneration, and exceeded the control level after 4 months (121.0% and 63.7% proximally and distally, respectively). The data indicate that the altered bidirectional transport of cholinergic marker proteins may be monitored quantitatively during nerve regeneration. This method might be suitable for studies of the nerve regeneration process.

Changes in acetylcholine content, release and muscarinic receptors in rat hippocampus under cold stress

The aim was to study the mechanism of the previously established decrease in acetylcholine (ACh) concentration in the rat hippocampus under cold stress. Male rats were exposed for 14 days to cold (5 degrees C) or kept (controls) at room temperature (24 degrees C). Acetylcholine content, release and muscarinic receptor binding were investigated in the hippocampus. Cold exposure resulted in a decrease of ACh concentration in the dorsal hippocampus. Moreover, the potassium-evoked release of ACh from hippocampal slices was increased and an increase of maximal binding capacity of [3H] (-) quinuclidinyl benzilate in the dorsal hippocampus of cold exposed animals was also observed. Thus the decrease of hippocampal ACh concentration under cold exposure is probably due to its increased release. On balance then, our results demonstrate that cold stress in the rat induces significant activation of the hippocampal cholinergic system.

[3H]-[H-D-Phe-Cys-Tyr-D-Trp-Orn-Thr-Pen-Thr-NH2] ([3H]CTOP), a potent and highly selective peptide for mu opioid receptors in rat brain

The cyclic, conformationally restricted octapeptide [3H]-[H-D-Phe-Cys-Tyr-D-Trp-Orn-Thr-Pen-Thr-NH2] ([3H]CTOP) was synthesized and its binding to mu opioid receptors was characterized in rat brain membrane preparations. Association rates (k+1) of 1.25 x 10(8) M-1 min-1 and 2.49 x 10(8) M-1 min-1 at 25 and 37 degrees C, respectively, were obtained, whereas dissociation rates (k-1) at the same temperatures were 1.93 x 10(-2) min-1 and 1.03 x 10(-1) min-1 at 25 and 37 degrees C, respectively. Saturation isotherms of [3H]CTOP binding to rat brain membranes gave apparent Kd values of 0.16 and 0.41 nM at 25 and 37 degrees C, respectively. Maximal number of binding sites in rat brain membranes were found to be 94 and 81 fmol/mg of protein at 25 and 37 degrees C, respectively. [3H]CTOP binding over a concentration range of 0.1 to 10 nM was best fit by a one site model consistent with binding to a single site. The general effect of different metal ions and guanyl-5'-yl-imidodiphosphate on [3H]CTOP binding was to reduce its affinity. High concentrations (100 mM) of sodium also produced a reduction of the apparent mu receptor density. Utilizing the delta opioid receptor specific peptide [3H]-[D-Pen2,D-Pen5]enkephalin, CTOP appeared to be about 2000-fold more specific for mu vs. delta opioid receptor than naloxone. Specific [3H]CTOP binding was inhibited by a large number of opioid or opiate ligands.(ABSTRACT TRUNCATED AT 250 WORDS)

Analgesic and tolerance-inducing effects of the highly selective delta opioid agonist [D-Pen2,D-Pen5]enkephalin in mice

The novel and highly selective, conformationally restricted enkephalin analogue for delta-opioid receptors, [D-Pen2,D-Pen5]enkephalin (DPDPE; Pen = penicillamine), was studied in various in vivo tests for analgesia, tolerance and physical dependence. Intracerebroventricular (i.c.v.) administration of DPDPE caused a dose-dependent, naloxone-reversible antinociception, measured with the heat-irradiant (tail-flick) method. Acute tolerance developed to the antinociceptive effect of DPDPE. DPDPE also caused mild signs of physical dependence (withdrawal hypothermia and body weight loss) after repeated peptide treatment. Severe signs of morphine withdrawal (e.g. withdrawal jumping) on the other hand, could not be reversed by the administration of DPDPE. It is concluded that the activation of central delta-opioid receptors may play a role in controlling pain mechanisms, and that this activation is followed by the rapid development of a tolerance to this action.

Central effects of the potent and highly selective mu opioid antagonist D-Phe-Cys-Tyr-D-Trp-Orn-Thr-Pen-Thr-NH2 (CTOP) in mice

The ability of the selective cyclic mu-opioid receptor antagonist, D-Phe-Cys-Tyr-D-Trp-Orn-Thr-Pen-Thr-NH2 (CTOP), to inhibit the acute and chronic effects of morphine in vivo was studied in mice. Intracerebroventricular (i.c.v.) administration of CTOP antagonized the analgesic effect of morphine in a dose-dependent manner, as measured by the heat-irradiant (tail-flick) method. CTOP was more effective than naloxone in inhibiting analgesia on a molar basis. CTOP also antagonized the acute morphine-induced hypermotility. CTOP caused withdrawal hypothermia and a loss of body weight in morphine-dependent animals. After the development of morphine-induced chronic dependence, CTOP administered i.c.v. caused a dose-dependent loss of body weight and hypothermia, and was about 10-400 times more potent than naloxone. CTOP administered alone to drugnaive mice did not cause antinociception, changes in body weight or body temperature.

[3H]AF-DX 116 labels subsets of muscarinic cholinergic receptors in rat brain and heart

The in vitro binding properties of the novel muscarinic antagonist [3H]AF-DX 116 were studied using a rapid filtration technique. Association and dissociation rates of [3H]AF-DX 116 binding were rapid at 25 degrees C (2.74 and 2.70 X 10(7) min-1 M-1 for K+1; 0.87 and 0.93 min-1 for k-1) but 20-40 times slower at 0-4 degrees C (0.13 and 0.096 X 10(7) min-1 M-1 for k+1; 0.031 and 0.022 min-1 for k-1 in cerebral cortical and cardiac membranes, respectively). Kinetic dissociation constants (Kds) were estimated to be 31.8 nM and 30.9 nM at 25 degrees C; 23.1 nM and 0-4 degrees C for the cerebral cortex and heart, respectively. In saturation studies, [3H]AF-DX 116 labeled 29 percent of the total [3H](-)QNB binding sites in the cerebral cortical membranes and 87 percent in the cardiac membranes, with Kd values of 28.9 nM and 17.9 nM, respectively. Muscarinic antagonists inhibited [3H]AF-DX 116 binding in a rank order of potency of atropine greater than dexetimide greater than AF-DX 116 greater than PZ greater than levetimide in both tissues. Except for PZ/[3H]AF-DX 116 and AF-DX 116/[3H]AF-DX 116 in the cerebral cortex, all the antagonist competition curves had Hill coefficients close to one. Carbachol and oxotremorine produced shallow inhibition curves against [3H]AF-DX 116 binding in both tissues. Regional distribution studies with [3H](-)QNB, [3H]PZ and [3H]AF-DX 116 showed that most of the muscarinic receptors in the cerebral cortex, hippocampus, nucleus accumbens and corpus striatum are of the M1 subtype while those in the brainstem, cerebellum and other lower brain regions are of the M2 subtype. These results indicate that [3H]AF-DX 116 is a useful probe for the study of heterogeneity of muscarinic cholinergic receptors.

Design and synthesis of conformationally constrained somatostatin analogues with high potency and specificity for mu opioid receptors

A series of cyclic, conformationally constrained peptides related to somatostatin were designed and synthesized in an effort to develop highly selective and potent peptides for the mu opioid receptor. The following new peptides were prepared and tested for their mu opioid receptor potency and selectively in rat brain binding assays: D-Phe-Cys-Tyr-D-Trp-Orn-Thr-Pen-Thr-NH2 (2, CTOP); D-Phe-Cys-Tyr-D-Trp-Arg-Thr-Pen-Thr-NH2 (3, CTAP); D-Phe-Cys-Tyr-D-Trp-Nle-Thr-Pen-Thr-NH2 (4); D-Phe-Cys-Tyr-D-Trp-Lys-Val-Pen-Thr-NH2 (5); D-Phe-Cys-Tyr-D-Trp-Lys-Gly-Pen-Thr-NH2 (6); D-Phe-Cys-Tyr-Trp-Lys-Thr-Pen-Thr-NH2 (7); D-Tyr-Cys-Tyr-D-Trp-Lys-Thr-Cys-Thr-OH (8); D-PhGly-Cys-Tyr-D-Trp-Lys-Thr-Pen-Thr-NH2 (9); and D-PhGly-Pen-Phe-D-Trp-Lys-Thr-Cys-Thr-OH (10). The most selective peptide, 2 (CTOP), displayed both high affinity (IC50 = 3.5 nM) and exceptional selectivity (IC50 delta/IC50 mu = 4,000) for mu opioid receptors. Furthermore, 2 exhibited very low affinity for somatostatin receptors in the rat brain (IC50 greater than 24,000 nM), with an IC50 somatostatin/IC50 mu receptor selectivity of 8,750. These conformationally constrained cyclic peptides should provide new insight into the structural and conformational requirements for the mu opioid receptor and the physiological role of this receptor.

Light microscopic autoradiographic localization of delta opioid receptors in the rat brain using a highly selective bis-penicillamine cyclic enkephalin analog

Light microscopic autoradiography was used to visualize the neuroanatomical distribution of rat brain delta opioid receptors. Slide-mounted sections of rat brain were labeled with [3H]-[2-D-penicillamine, 5-D-penicillamine]enkephalin([3H]DPDPE), a highly selective delta opioid agonist. Saturation isotherms of [3H]DPDPE binding to thaw-mounted brain slices gave a maximal number of binding sites of 79.9 fmol/mg of protein and an apparent dissociation constant (Kd) of 6.3 nM. DPDPE and met-enkephalin inhibited [3H]DPDPE binding with high affinity (lC50 values of 6.3 and 13.8 nM, respectively). Putative mu opioid receptor selective ligands such as morphine sulfate, Tyr-D-Ala-Gly-NMePhe-Gyl-ol and [N-MePhe3, D-Pro4]morphiceptin (PL017) were less potent inhibitors of [3H]DPDPE binding. The rat brain areas containing the highest densities of receptors were the claustrum, basolateral amygdaloid nucleus, the caudate-putamen and nucleus accumbens, the external plexiform layer of the olfactory bulb and the olfactory tubercle. Moderate receptor density was characteristic of the hippocampal formation in which grains were seen over the molecular layer of the dentate gyrus and stratum oriens (CA1), and of the different layers of cerebral cortex. Generally, low density of binding was found over the thalamus and the septal nuclei. Low specific binding was also seen in the cerebellum, medulla oblongata and in the dorsal horn of the spinal cord. There was little specific [3H]DPDPE binding over the white matter areas.

Cyclic somatostatin octapeptide analogues with high affinity and selectivity toward mu opioid receptors

A series of cyclic conformationally restricted penicillamine containing somatostatin octapeptide analogues have been prepared by standard solid phase synthetic techniques and tested for their ability to inhibit specific [125I]CGP 23,996 (des-Ala1-,Gly2-[desamino-Cys3Tyr11]-dicarba3, 14-somatostatin), [3H]naloxone or [3H]DPDPE ([D-Pen2-D-Pen5]enkephalin) binding in rat brain membrane preparations. We now report structure-activity relationship studies with the synthesis of our most potent and selective mu opioid receptor compound D-Phe-Cys-Tyr-D-Trp-Orn-Thr-Pen-Thr-NH2, which we refer to as Cys2Tyr3Orn5Pen7-amide. While this octapeptide exhibited high affinity (IC50 = 2.80 nM) for an apparently single population of binding sites (nH = 0.89 +/- 0.1) and exceptional selectivity for mu opioid receptors with an IC50(DPDPE)/IC50 (naloxone) ratio of 4,829, it also displayed very low affinity for somatostatin receptors (IC50 = 22,700 nM). Thus, Cys2Tyr3Orn5Pen7-amide may be the ligand of choice for further characterization of mu opioid receptors and for examining the physiological role of this class of receptors.

Light microscopic autoradiographic localization of somatostatin receptors in the rat brain

The binding parameters and distribution of somatostatin receptors were determined in the rat brain using in vitro light microscopic autoradiography. The proteolysis resistant somatostatin analog (des-Ala1-, Gly2-desamino-Cys3Tyr11-dicarba3,14-somatostatin; CGP 23,996) radiolabeled with 125iodine proved to be suitable for the localization of somatostatin receptors. Slide mounted tissue sections showed that 125I-CGP 23,996 bound to the somatostatin receptor with a mean Kd value of 4.0 nM. The mean density of receptors (maximum binding) was determined to be 182 fmol/mg of protein. Both somatostatin and unlabeled CGP 23,996 displayed high-affinity binding for somatostatin receptors with IC50 values of 6 and 5 nM, respectively. The areas containing the highest densities of receptors are the basal amygdaloid nucleus, medial habenular nucleus, stratum oriens and radiatum of CA1 and CA2, and the subiculum. High receptor density can also be found in the deep layers of the cingulate cortex and in the deep layers of temporal cortex. Moderate densities occur in the caudate-putamen, the granule cell layer of the cerebellum, CA3 area of the hippocampus, the molecular layer of the dentate gyrus and in the substantia nigra. Brain areas with low specific binding include the molecular layer of the cerebellum and the corpus callosum, a white matter area.

Modulation of the acetylcholine system in the superior cervical ganglion of rat: effects of GABA and hypoglossal nerve implantation after in vivo GABA treatment

gamma-Aminobutyric acid (GABA) was applied to the superior cervical ganglion (SCG) of CFY rats in vitro and in vivo, with or without implantation of a hypoglossal nerve, to evaluate the effects of these experimental interventions on the acetylcholine (ACh) system, which mainly serves the synaptic transmission of the preganglionic input. Long-lasting GABA microinfusion into the SCG in vivo apparently resulted in a "functional denervation." This treatment reduced the acetylcholinesterase (AChE; EC 3.1.1.7) activity by 30% (p less than 0.01) and transiently increased the number of nicotinic acetylcholine receptors, but had no significant effect on the choline acetyltransferase (acetyl-coenzyme A:choline-O-acetyltransferase; EC 2.3.1.6) activity, the ACh level, or the number of muscarinic acetylcholine receptors. The relative amounts of the different molecular forms of AChE did not change under these conditions. In vivo GABA application to the SCG with a hypoglossal nerve implanted in the presence of intact preganglionic afferent synapses exerted a significant modulatory effect on the AChE activity and its molecular forms. The "hyperinnervation" of the ganglia led to increases in the AChE activity (to 142.5%, p less than 0.01) and the 16S molecular form (to 200%, p less than 0.01). It is concluded that in vivo GABA microinfusion and GABA treatment in the presence of additional cholinergic synapses has a modulatory effect on the elements of the ACh system in the SCG of CFY rats.

Conformationally restricted cyclic analogues of substance P: insight into the receptor binding process

Three new cyclic substance P analogues were prepared to examine the possible role of a pseudocyclic turn structure for receptor recognition. In the guinea pig isolated ileum [Cys5, Cys11]-SP5-11-NH2 and [Cys6, Cys11]-SP5-11-NH2 were inactive at concentrations up to 100 microM, while [Cys5, Cys6, Nle11]-SP was a weak agonist. The order of relative affinities on the rat brain radioreceptor assay was as follows: [Cys5, Cys6, Nle11]-SP greater than [Cys5, Cys11]-SP5-11-NH2 greater than [Cys6, Cys11]-SP5-11-NH2. We interpret these results to indicate that a pseudocyclic structure of the 5-11 sequence may not be an important factor involved in the receptor recognition of substance P.