Modulation of Histamine Release in the Rat Brain by K-Opioid Receptors

The opioid modulation of histamine release was studied in rat brain slices labeled with L-[3H]histidine. The K(+)-induced [3H]histamine release from cortical slices was progressively inhibited by the preferential kappa-agonists ketocyclazocine, dynorphin A (1-13), Cambridge 20, spiradoline, U50,488H, and U69,593 in increasing concentrations. In contrast, the mu-agonists morphine, morphiceptin, and Tyr-D-Ala-Gly-(NMe)Phe-Gly-ol (DAGO) were ineffective as were the preferential delta-agonists [D-Ala2,D-Leu5]enkephalin (DA-DLE) and [D-Pen2,D-Pen5]enkephalin (DPDPE). Nor-binaltorphimine (nor-BNI) and MR 2266, two preferential kappa-antagonists, reversed the inhibitory effect of the various kappa-agonists more potently than did naloxone, with mean Ki values of 4 nM and 25 nM, respectively. The effects of ketocyclazocine and naloxone also were seen in slices of rat striatum, another brain region known to contain histaminergic nerve endings. We conclude that kappa-opioid receptors, presumably located on histaminergic axons, control histamine release in the brain. However, nor-BNI and naloxone failed, when added alone, to enhance significantly [3H]histamine release from cerebral cortex or striatum, and bestatin, an aminopeptidase inhibitor, failed to decrease K(+)-evoked [3H]histamine release. These two findings suggest that under basal conditions these kappa-opioid receptors are not tonically activated by endogenous dynorphin peptides. The inhibition of cerebral histamine release by kappa-agonists may mediate the sedative actions of these agents in vivo.     

Regulation of Histamine Release and Synthesis in the Brain by Muscarinic Receptors

The cholinergic modulation of histamine release and synthesis was studied in rat brain slices or synaptosomes labeled with L-[3H]histidine. Carbachol in increasing concentrations progressively reduced the K+-induced [3H]histamine release from cortical slices. Pirenzepine, a preferential M1-receptor antagonist, reversed the carbachol effect in an apparently competitive manner and with Ki values of 1-6 X 10(-8) M. 11-[(2-[(Diethylamino)methyl]-1-piperidinyl)acetyl]-5,11-dihydro-6H- pyrido[2,3-b][1,4]benzodiazepine-6-one (AF-DX 116), considered a preferential M2-receptor antagonist, reversed the carbachol effect with a mean Ki of approximately 2 X 10(-7) M. Oxotremorine behaved as a partial agonist in the modulation of histamine release. Neostigmine, an acetylcholinesterase inhibitor, inhibited the K+-induced release of [3H]histamine from cortical slices, and the effect was largely reversed by pirenzepine, an observation suggesting a modulation by endogenous acetylcholine. The effects of carbachol and pirenzepine were observed with slices of other brain regions known to contain histaminergic nerve terminals or perikarya, as well as with cortical synaptosomes. The two drugs also modified, in opposite directions, [3H]histamine formation in depolarized cortical slices. In vivo oxotremorine inhibited [3H]histamine formation in cerebral cortex, and this effect was reversed by scopolamine. When administered alone, scopolamine failed to enhance significantly the 3H- labeled amine formation, a finding suggesting that muscarinic receptors are not activated by endogenous acetylcholine released under basal conditions. It is concluded that muscarinic heteroreceptors, directly located on histaminergic nerve terminals, control release and synthesis of histamine in the brain. These receptors apparently belong to the broad M1-receptor category and may correspond to a receptor subclass displaying a rather high affinity for AF-DX 116.     

Linkage analysis of schizophrenia with five dopamine receptor genes in nine pedigrees

Alterations in dopamine neurotransmission have been strongly implicated in the pathogenesis of schizophrenia for nearly 2 decades. Recently, the genes for five dopamine receptors have been cloned and characterized, and genetic and physical map information has become available. Using these five loci as candidate genes, we have tested for genetic linkage to schizophrenia in nine multigenerational families which include multiple affected individuals. In addition to testing conservative disease models, we have used a neurophysiological indicator variable, the P50 auditory evoked response. Deficits in gating of the P50 response have been shown to segregate with schizophrenia in this sample and may identify carriers of gene(s) predisposing for schizophrenia. Linkage results were consistently negative, indicating that a defect at any of the actual receptor sites is unlikely to be a major contributor to schizophrenia in the nine families studied.     

A rapid assay for chloroplast-encoded triazine resistance in higher plants

We have designed a simple and rapid assay for chloroplast-based triazine resistance in higher plants using PCR amplification of thepsbA gene coupled toMaeI digestion of the amplified product to distinguish triazine resistant from sensitive biotypes. Our assay is universal and avoids the need of lengthy procedures of previously published assays, which either required spraying of seedlings in a controlled environment, quantification of chlorophyll fluorescence of leaf discs after incubation in triazine solution, DNA sequencing of thepsbA gene, or Southern-blot analysis. Our diagnostic system is qualitative, reliable, fast and simple. More than 100 seedlings taken directly from the field can be analyzed in one day. This system has a direct application towards a more rational use of herbicides in production fields. It also represents a valuable tool to monitor spreading of resistant biotypes through time and space and can serve as a model system applicable to other gene monitoring needs.     

Mating Call Discrimination in Female European (Coturnix c. coturnix) and Japanese Quail (Coturnix c. japonica)

Each year, thousands of domestic Japanese and hybrid quails are released within the breeding range of the European quail. We showed recently that no post‐zygotic isolating mechanisms have yet been established between these subspecies. The aim of this study was to investigate whether pre‐zygotic mechanisms are strong enough to prevent hybridization. We tested the level of subspecies selectivity in females of European and Japanese quail respectively using playbacks of European, hybrid and Japanese male mating calls. European quail females emitted the greatest number of rally calls in response to mating calls by conspecific males. Their responses were the weakest to mating calls produced by males of the other subspecies and intermediate to mating calls by hybrid males. In contrast, Japanese quails produced similar responses to all types of mating calls. These results suggest that mixed pairs could form in the wild. The European quail could thus become one of the most endangered galliforms of the Western Palearctic.     

Carbon source utilization of soil extracted microorganisms as a tool to detect the effects of soil supplemented with genetically engineered and non-engineered Corynebacterium glutamicum and a recombinant peptide at the community level

Abstract: Substrate utilization of microbial cells extracted from soil with a 0.85% aqueous sodium chloride solution, was determined to estimate effects on soil microorganisms at the community level with microtiter plates (Biolog GN®) containing 95 different sources of organic carbon. A consistent pattern of utilized substrates was obtained after 24 h of microtiter plate incubation at 28°C. The absorbance values (OD₅₉₀) obtained from a microtiter plate reader after background correction were transformed by using the average absorbance values of oxidized substrates as a threshold to distinguish between well utilized and poorly or non-utilized substrates and thereby reduce variances between replicates. Doubling times of the extracted soil microorganisms in the microtiter plates were tested with 12 substrates and ranged from 1.96 h to 3.23 h, depending on the carbon source. The carbon source utilization assay was used to assess the effects of soil inoculation with Corynebacterium glutamicum with and without a genetically engineered plasmid (pUN1; 6.3 kb), which encoded for the synthesis of the mammalian protease inhibiting peptide, aprotinin. Additionally, aprotinin itself was added at two concentrations to soil samples. An identical decrease in the number of carbon sources utilized, especially carbohydrates, occurred upon soil inoculation with both C. glutamicum strains after inoculation with 10⁶ cells g⁻¹ soil. This effect was only detectable during the first three weeks of incubation, as long as cell numbers of C. glutamicum (pUN1) were above 10⁵ cfu g⁻¹. Soil amendment with aprotinin resulted in utilization of additional substrates, most of them carbohydrates. With 0.1 mg aprotinin g⁻¹ soil this stimulation lasted 2 days and with 10 mg g⁻¹ it lasted for 7 days.     

Two Intracellular Signaling Pathways for the Dopamine D3 Receptor: Opposite and Synergistic Interactions with Cyclic AMP

Abstract: As cerebral neurons express the dopamine D₁ receptor positively coupled with adenylyl cyclase, together with the D₃ receptor, we have investigated in a heterologous cell expression system the relationships of cyclic AMP with D₃ receptor signaling pathways. In NG108-15 cells transfected with the human D₃ receptor cDNA, dopamine, quinpirole, and other dopamine receptor agonists inhibited cyclic AMP accumulation induced by forskolin. Quinpirole also increased mitogenesis, assessed by measuring [³H]thymidine incorporation. This effect was blocked partially by genistein, a tyrosine kinase inhibitor. Forskolin enhanced by 50–75% the quinpirole-induced [³H]thymidine incorporation. This effect was maximal with 100 n M forskolin, occurred after 6–16 h, was reproduced by cyclic AMP-permeable analogues, and was blocked by a protein kinase A inhibitor. Forskolin increased D₃ receptor expression up to 135%, but only after 16 h and at concentrations of >1 µ M . Thus, in this cell line, the D₃ receptor uses two distinct signaling pathways: it efficiently inhibits adenylyl cyclase and induces mitogenesis, an effect possibly involving tyrosine phosphorylation. Activation of the cyclic AMP cascade potentiates the D₃ receptor-mediated mitogenic response, through phosphorylation by a cyclic AMP-dependent kinase of a yet unidentified component. Hence, transduction of the D₃ receptor can involve both opposite and synergistic interactions with cyclic AMP.     

In vivo binding of 3H-pimozide in mouse striatum: Effects of dopamine agonists and antagonists

Several lines of evidence indicate that the i.v. injection of ³H-pimozide results in a specific in vivo binding of the neuroleptic to dopaminergic receptors.First, ³H-pimozide is preferentially accumulated in the striatum as compared to non-dopaminergic structures like the cerebellum. Second, the selective accumulation of ³H-pimozide is prevented by prior administration of various neuroleptics as well as by apomorphine. Moreover, doses of antagonists which prevent this accumulation were identical to those which lead to an increased striatal HVA level. Third, ³H-pimozide accumulation is not modified by the administration of a variety of non-dopaminergic agents.However, ³H-pimozide binding is not prevented either by indirect dopamine agonists and is even greatly increased by d-amphetamine at high doses. The possibility that direct or indirect dopamine agonists may favour the binding of the antagonist through a modification of receptor sites is discussed.     

The emerging roles of lactate as a redox substrate and signaling molecule in adipose tissues

Journal of Physiology and Biochemistry - Thermogenic (brown and beige) adipose tissues improve glucose and lipid homeostasis and therefore represent putative targets to cure obesity and related...