Bound forms of alkaloids in Papaver somniferum and P. Bracteatum

The polysaccharide fraction of the pericarp and seed of Papaver somniferum were shown to contain bound forms of morphine which were derived from radioactive morphine fed to living plants. Bound forms of codeine, thebaine and some unidentified alkaloid-like compounds were also detected in the pericarp and bound thebaine occurred in the pericarp of Papaver bracteatum. The complexity and molecular weight of the bound alkaloids seemed to increase during ripening, and it is suggested that these substances represent transitional forms in the metabolism and transiocation of morphine from latex to seed.     

Synergistic analgesic effects between neuronostatin and morphine at the supraspinal level

Neuronostatin, a 13-amino acid peptide, is encoded in the somatostatin pro-hormone. I.c.v. administration of neuronostatin produces a significant antinociceptive effect in the mouse tail-flick test, which is mediated by endogenous opioid receptor. However, the direct functional interaction between morphine and neuronostatin has not been characterized. In the present study, effect of neuronostatin on morphine analgesia was investigated in the tail-flick test. Our findings showed that i.c.v. administration of neuronostatin (0.3 nmol/mouse i.c.v.) significantly enhanced the antinociceptive effect of morphine (2.5, 5 or 10 μg/kg) at the supraspinal level. Results of antagonism experiments suggested that the synergistic analgesia induced by morphine and neuronostatin was mediated by μ- and к-opioid receptors not δ-opioid receptor. In conclusion, there may be a cascade amplification phenomenon when morphine and neuronostatin were co-administered in acute pain model. The above results provide evidence for the potential use of neuronostatin in combination with morphine to control pain and addiction.     

In vitro conversion of morphine to its N-oxide in Papaver somniferum latex

Radio active morphine (¹⁴C- and ³H-labelled) was fed in vitro to freshly collected samples of capsules and stem latex of Papaver somniferum and it was shown that some of it was converted to radioactive N-oxide. Although metabolic activity and variation between samples of latex collected at different times were much less marked than those previously found using in vivo methods, the results do confirm that the isolated latex is a metabolically viable tissue.     

Spontaneous Withdrawal from Long-Term Treatment with Morphine Accelerates the Turnover of α2-Adrenoceptors in the Rat Brain: Up-Regulation of Receptors Associated with Increased Receptor Appearance

Abstract: The aim of this study was to quantify and compare the turnover of brain α₂-adrenoceptors during chronic morphine treatment and after spontaneous morphine withdrawal in rats. The oral administration of increasing doses of morphine (10–90 mg/kg) for 20 days did not alter the specific binding of the agonist [³H]clonidine in the cerebral cortex. However, spontaneous opiate withdrawal (24 h) significantly increased the density of cortical α₂-adrenoceptors (B_max for [³H]clonidine was 21% greater). The recovery of [³H]clonidine binding after irreversible inactivation by N-ethoxycarbonyl-2-ethoxy-1,2-dihydroquinoline (1.6 mg/kg) was assessed in naive, morphine-dependent, and morphine-withdrawn rats to study the process of α₂-adrenoceptor repopulation and to calculate receptor turnover parameters. The simultaneous analysis of receptor recovery curves revealed that the turnover of brain α₂-adrenoceptors in morphine-withdrawn rats was accelerated [appearance rate constant (r) = 21 fmol/mg of protein/day; disappearance rate constant (k) = 0.25 day^?1] compared with those in morphine-dependent (r = 13 fmol/mg of protein/day; k = 0.14 day^?1) and naive (r = 15 fmol/mg of protein/day; k = 0.16 day^?1) rats. Moreover, this analysis also indicated that the increased density of cortical α₂-adrenoceptors observed during morphine withdrawal was due to a significantly higher receptor appearance (Δr = 37–57%) and not to a decreased receptor disappearance, which in fact showed also an increase (Δk = 56–79%). It is proposed that the increased rate of α₂-adrenoceptor production in the brain of morphine-dependent rats during spontaneous withdrawal is most probably mediated by the overactivity of the adenylyl cyclase/cyclic AMP system induced by opiate addiction.     

Modulation of 5-HT release by dynorphin mediates social deficits during opioid withdrawal

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Inhibitory Kcnip2 neurons of the spinal dorsal horn control behavioral sensitivity to environmental cold

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Insights into peptide and protein function: a convergent approach.

From viruses to multicellular organisms, life is inseparable from the genetic instructions aimed at regulating its maintenance, division, multiplication, differentiation and death (apoptosis). Over the past 15 years, structural studies have begun to resolve the complex reactions involved in these fundamental processes in biology. The three-dimensional representations of the complexes formed with peptides and/or proteins have allowed interpretation of the biochemical data and formulation of novel hypotheses about the control and execution of these processes. Moreover, they have opened the way to rational approaches for designing compounds able to interfere with these crucial events in normal or pathological conditions. Various results obtained in our laboratory in these fields are briefly summarized in this review.     

Morphine metabolism and normorphine in Papaver somniferum

Normorphine has been established as an active metabolite of morphine in P. somniferum. This was done by, (a) demonstrating the presence of normorphine throughout the life cycle of the plant, (b) finding normorphine-¹⁴C after feeding morphine-¹⁴C via the roots, and (c) exposing opium poppies to ¹⁴CO₂ under steady state conditions which led to morphine and normorphine of the same specific activity. Feeding normorphine-¹⁴C showed that the N-demethylation step is irreversible. A sensitive procedure was developed for the detection of normorphine in the presence of large amounts of morphine; using this procedure, normorphine was found in raw opium. These results indicate that the major, if not the sole, morphine degradative pathway involves an initial demethylation to normorphine, which is subsequently degraded to non-alkaloidal metabolites. The high rates of turnover observed led to the conclusion that the morphine alkaloids do play an active metabolic role, perhaps as specific methylating agents.     

Long-term potentiation in the anterior cingulate cortex and chronic pain

Glutamate is the primary excitatory transmitter of sensory transmission and perception in the central nervous system. Painful or noxious stimuli from the periphery ‘teach’ humans and animals to avoid potentially dangerous objects or environments, whereas tissue injury itself causes unnecessary chronic pain that can even last for long periods of time. Conventional pain medicines often fail to control chronic pain. Recent neurobiological studies suggest that synaptic plasticity taking place in sensory pathways, from spinal dorsal horn to cortical areas, contributes to chronic pain. Injuries trigger long-term potentiation of synaptic transmission in the spinal cord dorsal horn and anterior cingulate cortex, and such persistent potentiation does not require continuous neuronal activity from the periphery. At the synaptic level, potentiation of excitatory transmission caused by injuries may be mediated by the enhancement of glutamate release from presynaptic terminals and potentiated postsynaptic responses of AMPA receptors. Preventing, ‘erasing’ or reducing such potentiation may serve as a new mechanism to inhibit chronic pain in patients in the future.     

Stable fly, Stomoxys calcitrans, mouthpart removal influences stress and anticipatory responses in mice

Abstract Biting fly attack induces a variety of stress and anxiety related changes in the physiology and behaviour of the target animals. Significant reductions in pain, or more appropriately, nociceptive sensitivity (latency of a foot-lifting response to an aversive thermal stimulus), are evident in laboratory mice after a 1 h exposure to stable flies, Stomoxys calcitrans. The role of the various components of biting fly attack in the development of this stress-induced reduction in pain sensitivity (analgesia) is, however, unclear. This study demonstrates that fly-naive mice do not exhibit a stress-induced analgesia when exposed to stable flies whose biting mouthparts have been removed. In contrast, mice that have been previously exposed to intact stable flies exhibit significant analgesia when exposed to flies that are incapable of biting. However, the level of analgesia induced is lower than that elicited by exposure to intact stable flies. Exposure to non-biting house flies, Musca domestica , has no effect on nociceptive sensitivity. It appears that the actual bite of the stable fly is necessary for the induction of analgesia and probably other stress and anxiety associated responses in fly naive mice. However, mice rapidly learn to recognize biting flies and exhibit significant, possibly anticipatory analgesic responses to the mere presence of biting flies.