Science in drug control: the alkaloid content of afghan opium

Opium samples from Afghanistan were analyzed by HPLC for their content of morphine and three further alkaloids (codeine, thebaine, and papaverine). To our knowledge, this is the largest set of authentic opium samples analyzed in one study until now. The purpose was to assess possible correlations between samples and selected external factors, such as region of origin within Afghanistan, year of harvest, or intra-batch variation. In the investigated samples, a trend towards higher morphine concentrations in opium from the North-Eastern parts of Afghanistan was observed in the period from 2003 to 2005. More than 75% of the samples contained above 10% of morphine, the overall average was 14.4%.     

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Dosing‐time–dependent changes in the effect and toxicity of morphine were examined in mice housed under alternating 12 h light (07:00 to 19:00 h) and dark (19:00 to 07:00 h) cycles. Morphine (0.5 mg/kg) was injected intraperitoneally (i.p.) in animals to assess its beneficial effect (i.e., protection against the kaolin‐induced, bradykinin‐mediated, writhing reaction) and its toxicity (i.e., alteration of the hepatic enzymes of aspartate aminotransferase [AST] alanine aminotransferase [ALT], and glutathione [GSH] in separate experiments). The magnitude of the analgesic effect of morphine depended on dosing time, with minimum effect at 02:00 h and maximum effect at 14:00 h. The serum hepatic enzyme levels of AST and ALT increased after dosing morphine (100 mg/kg) at 02:00 and 14:00 h. Time courses of these enzymes did not differ between the two trials. However, hepatic GSH, which is involved in the detoxification of chemical compounds, significantly decreased after i.p. morphine injection at 02:00 but not at 14:00 h. Overall, the results suggest that the analgesic effect of morphine is greater after dosing during the resting than during the activity phase of mice that have been induced with bradykinin‐mediated pain. Drug‐induced hepatic damage as inferred by GSH alteration, however, may be greater after dosing during the active phase.     

Synthesis of iboga-like isoquinuclidines: Dual opioid receptors agonists having antinociceptive properties

Some novel iboga-analogues consisting of benzofuran moiety and dehydroisoquinuclidine ring connected by –CH₂–, (CH₂)₂ and (CH₂)₃ linkers have been synthesized with the view to develop potential antinociceptive drugs. The compounds 14 and 21 showed binding at the μ-opioid receptor (MOR), while the compound 11a exhibited dual affinities at both MOR and κ-opioid receptor (KOR). MAP kinase activation indicated all three compounds have opioid agonistic properties. The presence of a double bond and endo-methylcarboxylate group in the dehydroisoquinuclidine ring and the benzofuran and methylene spacer appeared to be essential for opioid receptor binding. Further studies demonstrated 11a caused significant antinociception in mice in the hot-plate test which was comparable to that produced by morphine. The compound 11a was also found to be nontremorigenic unlike various iboga congeners. This study identifies a new pharmacophore which may lead to the development of suitable substitute of morphine in the treatment of pain.     

Morphine Activates ω-Conotoxin-Sensitive Ca2+ Channels to Release Adenosine from Spinal Cord Synaptosomes

Abstract: Morphine-induced release of adenosine from the spinal cord is believed to contribute to spinal antinociception. Although this release is Ca²⁺ dependent, little is known of the nature of this dependence. In this study, the effects of the dihydropyridine L-type Ca²⁺ channel agonist Bay K 8644 and the antagonist nifedipine, the N-type Ca²⁺ channel antagonist ω-conotoxin, and ruthenium red, a blocker of Ca²⁺ influx induced by capsaicin, on release of adenosine evoked by morphine were determined. The effect of partial depolarization with a minimally effective concentration of K⁺ on morphine-evoked release of adenosine also was examined. Morphine 10^?5-10^?4M produced a dose-dependent enhancement of adenosine release from dorsal spinal cord synaptosomes. Following the addition of 6 mM K⁺ (total K⁺ concentration of 10.7 mM), 10^?6M morphine also enhanced release, and an additional component of action at 10^?8M was revealed. Release was Ca²⁺-dependent as it was not observed in the absence of Ca²⁺ and presence of EGTA. Bay K 8644 (10 nM) and nifedipine (100 nM) had no effect on the release of adenosine evoked by morphine, but ω-conotoxin (100 nM) markedly reduced such release in both the absence and the presence of the additional 6 mM K⁺. Morphine-evoked adenosine release was not altered in the presence of a partially effective dose of capsaicin, nor by ruthenium red. These results indicate that morphine can stimulate two distinct phases of adenosine release from the spinal cord (nanomolar and micromolar), and that both phases of release are due to Ca²⁺ entry via ω-conotoxin-sensitive N-type Ca²⁺ channels.     

Central and peripheral components of dermorphin's effect on rat intestinal propulsion in comparison to morphine

Dermorphin, injected intracerebroventricularly (ICV) to rats, provokes, like to morphine, an inhibition of intestinal propulsion linearly related to the log of the administered doses (in the range from 0.06 to 0.56 μg/rat), but it is 143 times more active than morphine. Naloxone, ICV or IP, antagonizes dermorphin less effectively than morphine. Quaternary naloxone ICV administered antagonizes the intestinal effect of ICV dermorphin, while IP administered it is not effective until 8 mg/kg. The dose of dermorphin maximally active by the ICV route (0.56 μg/rat) is completely inactive when injected IP. Increasing doses of dermorphin IP (from 12 to 6400 μg/kg) inhibit intestinal propulsion to the same extent irrespectively of the doses employed, but never by more than 50%. Only a high dose of naloxone (30 mg/kg/IP) antagonizes this IP effect. The central and peripheral components of this intestinal effect of dermorphin are discussed.     

Day-night rhythms in opiate modulation of body temperature in male Japanese quail

Summary Male Japanese quail,Coturnix coturnix japonica, displayed day-night rhythms in their body temperature, with significantly higher temperatures during the day than at night. There were individual variations in both the temperatures attained and amplitude of the day-night rhythm of body temperature in the group-housed birds. Accompanying these diurnal patterns in body temperature there were day-night rhythms in the effects of intraperitoneal administrations of the opiate agonist, morphine (1.0 and 10 mg·kg^-1) and prototypic opiate antagonist, naloxone (10 mg·kg^-1) on colonic body temperature. In the daytime, the body temperature response profiles of quail treated with morphine were dependent on the initial body temperature of the bird. In those birds with the lower daytime body temperatures, morphine caused an initial hyperthermic response that was followed by a hypothermia and then a weak hyperthermia; whereas, in birds with the higher initial body temperatures there was a pronounced hypothermia followed by a marked hyperthermia. At night, morphine induced a hyperthermic response in all quail that was followed by a hypothermia. These effects of morphine were blocked by naloxone, with naloxone by itself significantly decreasing the daytime temperature of those quail with the higher initial body temperature. Naloxone had no significant effects on the nighttime body temperatures of any of the quail. These results show that there are day-night rhythms and individual differences in opiate sensitivity and modulation of body temperature in male quail. These findings also suggest that endogenous opioid systems are involved in either the generation and/or expression of the day-night rhythm of body temperature in quail.Abbreviations LD light-dark - T _L low initial body temperatures - T _H high initial body temperatures     

α1Adrenoreceptpr-Mediated Increase in Acetylcholine Release in Braip Slices During Morphine Tolerance

Norepinephrine, clonidine, and phenylephrine increased the electrically evoked release of endogenous acetylcholine in cortical slices taken from morphine-tolerant guinea pigs. This effect was alpha 1-adrenoreceptor mediated and was opposite to the alpha 2-adrenoreceptor-mediated inhibition of acetylcholine release, normally elicited by norepinephrine and clonidine. In the presence of prazosin, clonidine recovered its normal inhibitory properties, suggesting that morphine tolerance induced the appearance of an alpha 1-adrenoreceptor-mediated response that overshadowed, but did not cancel, the still present alpha 2-adrenoreceptor inhibitory control. The attempt to prove the presence of alpha-adrenoreceptors on the nerve endings by testing the effect of norepinephrine in synaptosomal preparations (preloaded with [3H]choline and depolarized with KCl and veratridine) was unsuccessful. Therefore the problem of the exact location of this excitatory input remains to be solved. These results confirm previous findings reporting the increase in cortical acetylcholine release induced by the alpha-adrenoreceptor agonists in morphine-tolerant, freely moving guinea pigs and demonstrate that opiate tolerance inverts the direction of the noradrenergic modulation even in the isolated intracortical cholinergic structures.     

Changes in [3H]Nitrendipine Binding and γ-Aminobutyric Acid Release in Rat Hippocampus Following Repeated Morphine Administration

An antagonistic effect of calcium on the action of morphine was studied in rat hippocampal slices. The effect of repeated administration of morphine on gamma-aminobutyric acid (GABA) release and binding of [3H]nitrendipine, a calcium antagonist, was also examined. (1) In rat brain hippocampal slices, morphine enlarged the amplitude of the field potentials evoked in pyramidal neurons, disinhibiting them through basket cells. When the calcium concentration was elevated, potentiation of the field potentials by morphine was reduced. Decrease of the calcium concentration, on the other hand, enhanced the potentiating effect of morphine. Following repeated administration of morphine, its enhancing effect on the field potentials in slices was not observed. (2) In hippocampal membrane fractions obtained from rats repeatedly treated with morphine, enhancement of [3H]nitrendipine binding was observed. (3) In hippocampal slice preparations from rats receiving morphine repeatedly, K+ (45 mM)-stimulated [3H]GABA efflux was enhanced. The above results indicate that morphine antagonizes calcium, thereby reducing the release of transmitters. Furthermore, increase in calcium channels following repeated treatment of rats with morphine may explain the mechanism underlying development of tolerance.     

Attenuation of morphine analgesia by α-MSH,MIF-I,melatonin and naloxone in the rat

In two experiments the effects of the pituitary peptide α-MSH, the hypothalamic tripeptide MIF-I (P-L-G-NH₂) and the pineal hormone melatonin were investigated on the attenuation of morphine analgesia measured by a tail flick test. In Experiment 1, α-MSH had minimal effect on morphine analgesia, whereas, MIF-I and melatonin clearly delayed the onset of morphine analgesia, and melatonin also shortened the duration of analgesia. Experiment 2 was designed to investigate the possible synergistic effect of MIF-I and melatonin. The combined treatment of MIF-I and melatonin significantly delayed the onset of morphine analgesia, and melatonin alone shortened the duration of analgesia. The relationshps among the pituitary, hypothalamus and the pineal for the modulation of pain and response to morphine were discussed.     

Simultaneous Measurement of Extracellular Morphine and Serotonin in Brain Tissue and CSF by Microdialysis in Awake Rats

In this report, we describe an HPLC with electrochemical detection assay for the simultaneous measurement of levels of morphine, serotonin, 5-hydroxyindole-3-acetic acid, and homovanillic acid in dialysates of various brain areas and CSF in the awake rat. Morphine could be detected in the dialysates after a single intraperitoneal injection, with doses as low as 1.0 mg/kg. The time course of extracellular morphine content in the lateral hypothalamus, striatum, cerebellum, periaqueductal gray, and dorsal horn of the spinal cord and in CSF, from the ventricles and cisterna magna, was similar. We detected morphine in the first 15-min sample, and levels peaked 45-60 min after injection. Maximal dialysate levels, however, varied with the type of dialysis probe used and the area sampled. The most efficient in vivo recovery was in CSF dialysates from the cisterna magna, presumably because of minimal tissue interference with the dialysis probe. For this reason, the cisterna is an ideal region for sampling CSF. Morphine had no significant effect on the extracellular concentrations of serotonin in any of the areas studied and did not modify or only slightly increased levels of tissue metabolites; however, morphine markedly increased the CSF levels of 5-hydroxyindole-3-acetic acid and homovanillic acid. Because microdialysis in freely moving animals permits assessment of the behavioral effects of morphine while continuously monitoring the drug levels in discrete brain regions, this approach will greatly facilitate future studies of the neurochemical basis of morphine's effects in the brain.