Anti-mu opioid antiserum against the third external loop of the cloned mu-opioid receptor acts as a mu receptor neutral antagonist

The region from the third external loop to the C terminus of MOR-1 appeared to be critical to the selective binding of MOR-1 ligands as DAMGO and morphine to MOR-1. To study the pharmacological properties of the third extracellular loop an antibody was raised in rabbits against the sequence 304-316 which is unique to MOR-1 and includes the third external loop; the anti-MOR-1 antibody was affinity purified against the immunogen sequence and characterized by [3H]DAMGO and Western blotting; [3H]DPDPE binding assay remained unchanged in the presence of the antibody. Anti-MOR-1 IgG was characterized as a neutral antagonist in Chinese hamster ovary (CHO) cells hyperexpressing constitutively active MOR-1s; in fact, anti-MOR-1 IgG completely reversed the inhibition induced by the MOR-1 agonist endomorphin1, endomorphin2, DAMGO and morphine on forskolin stimulated cyclic AMP (cAMP) accumulation and attenuated both the action of the selective MOR-1 agonist DAMGO to increase [35S]GTPgammaS binding and the action of the MOR-1 inverse agonist beta-chlornaltrexamine (CNA) to decrease [35S]GTPgammaS binding. Radioligand binding assay using membrane suspensions from CHO cells hyperexpressing MOR-1 revealed a significant decreased binding affinity and capacity of all the tested MOR-1 selective ligands after preincubation with anti-MOR-1 IgG. Therefore, the third extracellular loop of MOR-1 appeared to be a key element for the binding of MOR-1 ligands.

Endogenous morphine modulates acute thermonociception in mice

The endogenous synthesis of morphine has been clearly demonstrated throughout the phylogenesis of the nervous system of mammals and lower animals. Endogenous morphine, serving as either a neurotransmitter or neurohormone, has been demonstrated in the nervous system of both vertebrates and invertebrates. As one of the effects of exogenous morphine is the modulation of pain perception, we investigated the effects that the depletion of endogenous morphine had on nociceptive transmission. The immunoneutralization of endogenous morphine from brain extracellular spaces was obtained through the intracerebroventricular administration of affinity purified anti-morphine IgG to mice, which then underwent the hot plate test. Endogenous morphine immunoneutralization decreased thermal response latency and attenuated the anti-nociceptive effect of the mu selective agonist DAMGO in hot plate test suggesting that endogenous morphine is involved in pain modulation.

Corpus callosum agenesis, multiple cysts, skin defects, and subtle ocular abnormalities with a de novo mutation [45,XX,der(5), t(5;;14) (pter;q11.2)]

We report on a 2-year-old girl with a de novo mutation [45,XX,der(5),t(5;14) (pter;q11.2)] with corpus callosum agenesis, multiple cysts (cerebral and cardiac), subtle eye abnormalities, and at least two different skin defects, strongly indicating neuroectodermal involvement, as a neuromuscular choristoma (hamartoma) and an eccrine hamartoma. Fluorescent in situ hybridization with different single-locus probes showed that chromosome 5 has a very small deletion, confined to a region composed of repetitive sequences. By contrast, the long (q) arm of chromosome 14 seems to be much more involved in the rearrangement, with partial monosomy spanning from the centromere to the D14S72 and D14S261 loci. The extent of the deleted region of chromosome 14 is approximately 16 cM. To our knowledge, this is the smallest reported deletion involving the chromosome 14q11.2 region to be associated with a developmental disorder resulting in variable eye, skin, and brain anomalies. We suggest that a new syndrome, mimicking in some ways the MLS phenotype, is caused by a deletion in the chromosome 14q11.2 region.

Endogenous morphine

It is now well accepted that endogenous morphine is present in animals, both in invertebrates and vertebrates. It is a key signaling molecule that plays an important role in downregulating physiological responses, such as those in the immune system, including immune elements in the CNS. It has been demonstrated that a specific mu-opiate-receptor subtype, mu3, mediates these downregulatory effects through release of NO. This article examines morphine as an endogenous signaling molecule, in terms of its role in neural and immune regulation.

Endogenous morphine levels increase in molluscan neural and immune tissues after physical trauma

The aim of this study was to demonstrate by biochemical and immunocytochemical methods the presence of endogenous morphine in nervous and immune tissues of the freshwater snail, Planorbarius corneus. High performance liquid chromatography (HPLC) coupled to electrochemical detection performed on tissues from control snails, revealed that the CNS contains 6.20+/-2.0 pmol/g of the alkaloid, the foot tissue contains a much lower level, 0.30+/-0.03 pmol/g, whilst morphine is not detected in the hemolymph and hepatopancreas. In specimens that were traumatized, we detected a significant rise of the CNS morphine level 24 h later (43.7+/-5.2 pmol/g) and an initial decrease after 48 h (19.3+/-4.6 pmol/g). At the same times, we found the appearance of the opiate in the hemolymph (0.38+/-0.04 pmol/ml and 0.12+/-0.03 pmol/ml) but not in the hepatopancreas. Using indirect immunocytochemistry, a morphine-like molecule was localized to a number of neurons and a type of glial cell in the CNS, to some immunocytes in the hemolymph and to amoebocytes in the foot, as well as to fibers in the aorta wall. Simultaneously to the rise of morphine biochemical level following trauma, morphine-like immunoreactivity (MIR) increased in both intensity and the number of structures responding positively, i.e., neurons and fiber terminals. In another mollusc, the mussel Mytilus galloprovincialis, the same pattern of enhanced MIR was found after trauma. Taken together, the data suggest the presence of a morphinergic signaling in invertebrate neural and immune processes resembling those of classical messenger systems and an involvement in trauma response.

Potassium-induced release of endogenous morphine from rat brain slices

Endogenous morphine has been clearly demonstrated by gas chromatography/mass spectrometry in the brain, spinal fluid, adrenal glands, and liver of mammals. To clarify the role of endogenous morphine, its release from rat brain slices was studied in vitro in the presence of high potassium concentrations, with and without calcium in the medium. The perfusate was hydrolyzed, solid phase-extracted, and then analyzed by gas chromatography/mass spectrometry. Depolarization due to high potassium concentrations increased the release of the alkaloid manyfold with respect to the basal value, and the release was dependent on the presence of calcium in the medium. These results suggest that endogenous morphine might act as a neurotransmitter or neuromodulator in the rat CNS.

Immunocytochemical localization of endogenous codeine and morphine

Experiments carried out by indirect immunofluorescence and unlabelled antibody enzyme procedures revealed the presence of morphine-like immunoreactive material in the perikarya, fibers, and terminals of neurons in different, discrete areas of rat and human brain. The monoclonal and polyclonal anti-morphine antibodies used do not distinguish between morphine and codeine. Endogenous morphine seems to be stored in neurons as the 3-ethereal sulphate conjugate. This possibility is supported by the finding that, although active uptake of [3H]morphine has not been detected in brain synaptosomes, long-term i.c.v. injection of the tritiated opiate results in the accumulation of radioactivity inside the same neurons in which the endogenous alkaloids have been detected. Finally, striatal slices exposed to high K+ concentrations showed a rapid disappearance of the morphine-like immunoreactive material from neurons, indicating that endogenous alkaloids are released from neurons by depolarization.

Endogenous codeine and morphine are stored in specific brain neurons

Codeine and morphine have been detected in mammalian brain by radioimmunoassay (RIA), and in brain and other tissues by gas-chromatography/mass-spectrometry (GCMS) in different laboratories. It has been also shown that rat liver can synthesize the skeleton of the morphine molecule, thus suggesting that this alkaloid, which is the prototype of mu-receptor agonists, plays a physiological role in brain. We report the presence of morphine-like immunoreactive compounds inside the cell body, fibers and terminals of neurons in different brain areas. Moreover, neurons localized in the same brain areas were capable of accumulating and storing [3H]morphine slowly infused intracerebroventricularly (i.c.v.) through an osmotic minipump.

Peptidergic innervation of mesenteric lymphatics in guinea pigs: an immunocytochemical and pharmacological study

By immunocytochemistry, substance P immunoreactive (SP-IR) and vasoactive intestinal peptide immunoreactive (VIP-IR) nerve fibers were examined in guinea pig mesenteric lymph collectors. The immunoreactive nerve fibers, located in the adventitia of lymphatics, were few and were irregularly distributed along the vessel wall. These fibers appeared to be more numerous and more evenly distributed along the corresponding artery and vein walls within the same area. SP immunoreactivity in the vascular nerves was depleted in guinea pigs injected with capsaicin but was unaffected by the injection of 6-hydroxydopamine. By contrast, VIP-IR nerve fibers were unaffected by both treatments. It is concluded that SP-IR nerve fibers in the lymphatics are likely to be of sensory origin and that VIP containing nerves in the lymph collectors are distinct from SP-containing and noradrenergic nerves. It is also suggested that lymph collectors possess a complex although limited innervation pattern not only of autonomic nerve fibers containing classic neurotransmitters but also of peptidergic nerve fibers of a different origin with a vasomotor and/or sensory action.