Microwave-induced and pharmacological suppression of somatic pain under conditions of the formalin test in mice

We examined pain-related behavioral reactions and non-pain behavioral manifestations in mice under conditions of the formalin test. Levels of analgesia induced by i.p. injections of analgin, microwave irradiation of an antinociceptive acupuncture point (AP), E-36, or combined application of the above factors were measured. The duration of the pain behavioral reaction (licking of the injured limb) decreased due to irradiation of the AP with microwaves and to injection of 8.3 mg/kg analgin by 24.3% and 53.8%, on average, respectively. Combination of injection of analgin in a smaller dose (4.2 mg/kg) and microwave irradiation of the AP suppressed manifestations of the pain behavioral reaction by 43.4%. Thus, combination of pharmacologically induced analgesia with the action of microwaves on the antinociceptive AP allows one to significantly decrease the doses of analgesic preparations necessary to provide a full-level analgesic effect; in such a way, side effects of the respective drugs can be weakened. Neirofiziologiya/Neurophysiology, Vol. 38, No. 1, pp. 46–51, January–February, 2006.     

Suppression of synthesis of serotonin: Effect on antinociception induced by microwave irradiation and analgesic remedies

We studied isolated and combined antinociceptive effects of analgesics (Analginum and Tramadol), as well as of microwave irradiation of an acupuncture point, in mice under conditions of suppression of synthesis of serotonin by an inhibitor of this synthesis, DL-p-chlorophenylalanine (p-CPA). Preliminary introduction of p-CPA weakened the antinociceptive effect of microwave irradiation and also moderated the combined effects of analgesics and microwave irradiation. Neirofiziologiya/Neurophysiology, Vol. 38, Nos. 5/6, pp. 498–499, September–December, 2006.     

Analgesia induced by combined action of Tramadol and microwave irradiation in somatic pain in mice

In experiments on albino male mice weighing 24 to 32 g, we studied the suppression of the pain reaction induced by injection of formalin into the dorsal surface of the foot, using a combination of injection of tramadol hydrochloride (Tramal) in a dose of 0.42 mg/kg and irradiation of the acupuncture point (AP) E-36 with low-intensity microwaves (frequency 30 to 300 GHz and power rate density 3·10⁻⁹ W/cm²). The combined use of tramadol injection and the action of microwaves on the AP led to a decrease in the duration of the pain reaction (licking of the pain nidus), on average, by 58.2%, as compared with that in the control animal group. The analgesic effect was more strong in the case of such a combination than after isolated injection of tramadol in doses of 0.83 and 0.42 mg/kg (by 14.4 and by 10.0%, respectively) and isolated microwave irradiation of the AP TA E-36 (by 48.7%). The data obtained demonstrate the possibility of effective analgesia using a combination of microwave irradiation of the AP and the pharmacological influence with a significant decrease in the dose of the analgesic. Neirofiziologiya/Neurophysiology, Vol. 38, No. 4, pp. 314–319, July–August, 2006.     

Involvement of the serotonergic cerebral system in microwave-induced analgesia in mice of different genotypes

Under conditions of the formalin test, we studied changes in the level of analgesia induced by the action of low-intensity microwaves on the antinociceptive acupuncture point (AP) E36 in mice of strains CBA/CaLac (CBA) and C57BL/6j (C57) and in albino mongrel mice. Measurements were performed under control conditions and with experimentally induced decrease in the serotonin level in the brain (by injections of DL-parachlorophenylalanine, p-CPA). In the latter cases, the duration of the pain behavioral reaction increased despite irradiation of the AP E36. In mongrel, CBA, and C57 mice, the intensity of pain manifestations was 114.4, 29.0, and 21.1% greater, respectively, than in mice of these groups with no injections of p-CPA. These facts show that the serotonergic brain system is profoundly involved in the formation of analgesia after irradiation of the AP by low-intensity microwaves, and this involvement significantly depends on the genotype of the animals. Neirofiziologiya/Neurophysiology, Vol. 38, Nos. 5/6, pp. 495–497, September–December, 2006.     

Involvement of the Serotonergic System in Analgesia Induced by the Influence of Low-Intensity Microwaves on an Antipain Acupuncture Point

In experiments on mice, we studied changes in the level of analgesia induced by irradiation of the antipain acupuncture point (AP) E36 by low-intensity microwaves under conditions of modification of the serotonin level in the brain; this level was modified by injection of 300 mg/kg DL-p-chlorophenylalanine (pCPA). The duration of the nociceptive behavioral reaction (licking the limb) caused by injection of the formalin solution into the foot dorsal surface increased 24, 48, and 72 h after pCPA injection by 99.9, 84.4, and 114.4%, as compared with those in animals subjected to microwave irradiation of the AP E36 with no preliminary pCPA injection. It is concluded that the brain serotonergic system is actively involved in the analgesia effects induced by irradiation of the AP by low-intensity microwaves.     

p-CPA enhances growth and quality of muskelon fruits

The effects of para-chlorophenoxyacetic acid(p-CPA) application in improving the reduction in growthrate and sugar accumulation, and on the peel color and firmness ofparthenocarpic fruit, and its residual content in the treated fruit wereexamined. p-CPA application to parthenocarpic fruit duringthe rapid growth stage [5 or 10 days after anthesis (DAA)] enhanced the fruitweight, but was ineffective when applied at 40 DAA. p-CPA– promoting of fruit growth increased as the applied concentration rose,so the weight of fruit treated by p-CPA at 500 mgL^–1 (the highest level) was the greatest in all plots;however the peel was considerably softer and abnormal swelling occurred in thenet. p-CPA applied to parthenocarpic fruit from 5 to 25DAAincreased sucrose content, the most effective application time being justbeforethe onset of sucrose accumulation (25 DAA). Fructose and glucose contents wereconsiderably lower than that of sucrose, and were not affected byp-CPA. p-CPA promoted sucroseaccumulation when applied to pollinated fruit, which showed the highest levelofenhancement in all plots. During the maturation period, the peel ofparthenocarpic fruit was a darker green color and the netting did not fullydevelop compared to pollinated fruit. p-CPA applicationsat10 or 25 DAA improved the peel color and netting of parthenocarpic fruits;therefore, the L value was similar to that of seeded fruit and the hue angledeclined. Applications of p-CPA during the early growthstage reduced the firmness of the mesocarp concomitant with increases in theapplied concentrations. p-CPA was present in the fruit atharvest, when applied from 10 to 25 DAA, even at 20 mgL^–1. The residue level increased as the appliedconcentration rose, but p-CPA was not detected in thenon-treated plot.     

Antinociceptive effects of morphine and naloxone in mu-opioid receptor knockout mice transfected with the MORS196A gene

Background  

Opioid analgesics such as morphine and meperidine have been used to control moderate to severe pain for many years. However, these opioids have many side effects, including the development of tolerance and dependence after long-term use, which has limited their clinical use. We previously reported that mutations in the mu-opioid receptors (MOR) S196L and S196A rendered them responsive to the opioid antagonist naloxone without altering the agonist phenotype. In MORS196A knock-in mice, naloxone and naltrexone were antinociceptive but did not cause tolerance or physical dependence. In this study we delivery this mutated MOR gene into pain related pathway to confirm the possibility of in vivo transfecting MORS196A gene and using naloxone as a new analgesic agent.     

Augmented analgesic effects of L-tryptophan combined with low current transcranial electrostimulation

The analgesic effects of low current transcranial electrostimulation are both naloxone and pCPA-reversible, suggesting that they may be mediated in part by endogenous opioid and serotonergic activity. The present experiments indicate that pretreatment with the serotonin precursor L-tryptophan results in an increased analgesic effect of electrostimulation as measured by the 50 degrees C wet tail flick test in the rat. Rats receiving both L-tryptophan and electrostimulation displayed significantly more analgesia than rats receiving electrostimulation and injection vehicle alone, rats receiving drug and sham stimulation or rats receiving vehicle and sham stimulation.     

Evidence that Inhibition of Nicotine-Mediated Catecholamine Secretion from Adrenal Chromaffin Cells by Enkephalin, β-Endorphin, Dynorphin (1-13), and Opiates is not Mediated via Specific Opiate Receptors

Abstract: The opioid peptides Met- and Leu-enkephalin, dynorphin (1-13), and β-endorphin and the narcotic analgesics, morphine, levorphanol, and dextrorphan all produced a dose-dependent inhibition of nicotine (5 × 10^?6m )-mediated release of [³H]norepinephrine ([³H]NE) from bovine adrenal chromaffin cells in culture. None of these agents affected [³H]NE release induced by high K⁺ (56 mm ). Although the above results suggest that the opioid peptides and narcotic analgesics inhibit catecholamine release from adrenal chromaffin cells in culture, we suggest that these effects are not mediated by specific opiate binding sites, since (1) the inhibition was only produced with high concentrations of the agents—the threshold concentrations were 10^?7 to 10^?5m and higher; (2) the inhibition produced by the narcotic analgesics did not display stereospecificity, because the (d-isomer, dextrorphan, was slightly more active than the l-isomer, levorphanol; (3) the narcotic antagonists naloxone, naltrexone, and levallorphan did not reverse the inhibition produced by either the narcotic analgesics (e.g., morphine) or the opioid peptides (e.g., dynorphin). These three antagonists themselves inhibited the nicotine-mediated release of [³H]NE from the adrenal chromaffin cells in culture. Finally (4), the I₂-Tyr¹ substituted analogues of β-endorphin and dynorphin that are biologically less active than the parent compounds produced an inhibition of the nicotine-mediated [³H]NE release similar to that of their parent compounds. These results do not support the idea that high-affinity stereospecific opiate binding sites are involved in the inhibitory modulation of nicotinic evoked catecholamine release from bovine adrenal chromaffin cells in culture.     

Comparative analysis of analgesic activities of dermorphin, [DPro<Superscript>6</Superscript>]-dermorphin,and their C-terminal tripeptides

Analgesic activities of dermorphin (DM), [DPro⁶]-DM, and their C-terminal tripeptides were comparatively studied. Analgesic activity was evaluated in tail flick, hot plate, tail pinch, formalin, and acetic acid writhing tests describing different levels of organization of pain sensitivity. Intraperitoneal administration of the peptides decreased the pain threshold in all these tests. The C-terminal tripeptides DM_5–7 and [DPro⁶]-DM_5–7 demonstrated analgesics activity comparable or sometimes higher than that of the full-length molecules. The effect of DM, [DPro⁶]-DM, and C-terminals fragments DM_5–7 and [DPro⁶]-DM_5–7 decreased after co-administration with naloxone, which points to the opioid nature of analgesic activity of the peptides.     

Synthesis and analgesic effects of novel β2-tryptophan hexapeptide analogs

Aiming to develop more potent analgesic substances a new series of hexapeptides containing β²-tryptophan analogues was synthesized. The Trp in position 4 and 5, respectively in Ac-Arg-Phe-Met-Trp-Met-Lys-NH₂ (opioid receptor antagonist) and Ac-Arg-Tyr-Tyr-Arg-Trp-Lys-NH₂ (highly potent and selective NOP-receptor agonist) was substituted by the (S)-2-(1-methyl-1H-indol-3-yl)propionic residue or the (S)-2-(5-methoxy-1H-indol-3-yl)propionic residue. The analgesic effect of the four newly synthesized compounds has been evaluated in male Wistar rats by PP- and HP tests and compared to the native templates. Further estimation of the mechanisms of action of each compound was achieved using specific antagonists—naloxone for opioid and JTC801 for the NOP receptor. Replacement of Trp with β²-tryptophan analogues in 4th position (Ac-Arg-Phe-Met-Trp-Met-Lys-NH₂) led to increased and longer lasting analgesic effect. The results obtained permit us to assume that both opioid and NOP receptors take part in the newly synthesized compounds analgesic effects.     

Effects of Peptide and Non-Peptide Opioids on Protective Reaction of the Cockroach Periplaneta americana in the “Hot Camera”

The ability of morphine, naloxone, and several opioid peptides of the group of beta-casomorphines to change the time of the stay of cockroaches Periplaneta americana in a hot camera (t = 47°C) was studied. It has been shown that the morphine dose ED₅₀ increasing twice the stay amounts to 200 µg/g, while hat of naloxone, to 40, of heptapeptide YPFPGPI, to 440, and of pentapeptide YPFPG, to 420 µg/g. Hexapeptide YPFPGP free of the N-terminal tyrosine had no statistically significant effect on the stay duration. The earlier changes of the stay duration (in 15–60 min after injection; the most pronounced for morphine and naloxone) corresponded to the ability of these drugs to act on the mu-type opioid receptors. The high peptide affinity to the delta-type receptors led to development of the later effects (in 90–150 min after injection; the most pronounced for heptapeptide YPFPGPI). A combined injection of naloxone and heptapeptide lead to the mutual inhibition of their effect: the peptide eliminated the early effect of naloxone on the stay duration, whereas naloxone, the late effects of beta-casomorphine. The obtained results indicate an important role of the endogenous opioid system in control of protective behavior of insects, as well as heterogeneity of the receptor components of the system.     

Response of sucrose metabolizing enzyme activity to CPPU and p-CPA treatments in excised discs of muskmelon

We investigated the effects of 1-(2-chloro-4-pyridyl)-3-phenylurea(CPPU) and para-chlorophenoxyacetic acid(p-CPA) treatments on the sucrose metabolism-relatedenzymeactivities in excised mesocarp discs of muskmelon fruit at different growthstages. Both a CPPU and a p-CPA treatment applied to discsprepared at 5 and at 20 days after anthesis (DAA) increased acid invertase (AI)activity and neutral invertase (NI) activity, but neither treatment affectedthese activities in the discs prepared at 45 DAA. Both plant growth substancesincreased the activity of sucrose phosphate synthase (SPS) in the discs at 5and20 DAA, but neither affected it in the 45 DAA discs. The sucrose synthase (SS)activity was markedly increased by p-CPA treatment in the20 and 45 DAA discs, but was not affected at 5 DAA. CPPU treatment did notactivate SS of discs throughout the growth stage.     

Inhibition of an opioid-evoked vagal reflex in rats by naloxone,SMS 201-995 and ICI 154,129

Intravenous injection of opioid agonists in rats evokes a vagal reflex resulting in a fall in heart rate and blood pressure. Three opioid antagonists, naloxone, SMS 201-995, and ICI 154,129 were used to assess the nature of the opioid receptors that mediate the vagal reflex. The agonists used were morphine, Tyr-Pro-NMePhe-d-Pro-NH₂ (PLO17), and d-Ala²-Leu⁵-enkephalin (DADL). At challenge doses of morphine, PLO17, and DADL at five times the ED50 for bradycardia, the naloxone ED50 for DADL was nine times greater than that for morphine and PLO17. The pA₂ value of naloxone against DADL was significantly less than that for morphine and PLO17. The antagonist properties of SMS 201-995 were similar to those of naloxone. ICI 154,129, a putative delta receptor antagonist, was not, however, selective in its antagonism of opioid bradycardia. Both SMS 201-995 and ICI 154,129, when injected alone, produced changes in heart rate and blood pressure. The cardiovascular actions of the peptide antagonists were not affected by naloxone hydrochloride at doses up to 4 mg/kg i.v.     

A physicochemical study of the interaction of phosphatidylinositol with buprenorphine and naloxone

The interactions of two opioid molecules (buprenorphine and naloxone) with phosphatidylinositol and phosphatidylcholine were studied in lipid monolayers at the air-water interface. The influence of Na⁺, Ca²⁺, and Mn²⁺ ions in these interactions has also been determined. Neither buprenorphine nor naloxone influence the ordered state of phosphatidylcholine monolayers. On the contrary, both opioid molecules interact specifically with phosphatidylinositol monolayers. The area/molecule of phosphatidylinositol spread on buprenorphine containing subphases is highly affected by this molecule and also by ions. The phosphatidylinositol/naloxone interactions are rather weak and less affected by ions.Abbreviations PI phosphatidylinositol - PC phosphatidylcholine - Bup Buprenorphine - Nx naloxone - ODS octadecyl silica - k capacity factor - logP partition coefficient between octanol and water     

Alternative Forms of Interaction of Substance P and Opioids in Nociceptive Transmission

Summary Many years preclinical and clinical anatomic, pharmacologic, and physiologic studies suggest that SP- and opioid-expressing neurons produce opposite biological effects at the spinal level, i.e., nociception and antinociception, respectively. However, in certain circumstances intrathecally administered SP is capable of reinforcing of spinal morphine analgesia and may therefore function as an opioid adjuvantin vivo. The SP dose-response curve of spinally administered SP follows a bell-shaped or inverted-U configuration, permitting pharmacological dissociation of opioid-potentiating and analgesic properties of SP from traditional hyperalgesic effects seen at significantly higher concentrations. This analgesic effect is blocked by naloxone but unaffected by transection of the spinal cord, thus demonstrating the lack of supraspinal modulation. The present report briefly describes both reinforcing and opposing interactions between multiple opioid systems and substance P at the spinal level. We propose that a likely mechanism underlying SP-mediated enhancement of opioid analgesia is the ability of SP to release endogenous opioid peptides within the local spinal cord environment.     

Comparison of the behavioral effects of β-endorphin and enkephalin analogs

The behavioral effects of β-endorphin, enkephalin analogs, morphine and etorphine were briefly compared. In the tail-flick test in mice and in the wet shake test in rats, β-endorphin and D-Ala²-D-Leu⁵-enkephalin had equal antinociceptive activity; D-Ala² -Met-enkephalinamide and D-Leu⁵-enkephalin were less active. The order of activity of the enkephalin analogs and opiate alkaloids for stimulating locomotor activity in mice paralleled their analgesic activities; β-endorphin, however, had only minimal stimulatory actions. Morphine sulfate, 50 μg injected into the periaqueductal gray, produced hyperactivity but this effect was not observed with etorphine or opioid peptides. By contrast, “wet dog” shakes was observed with the opioid peptides but not with either opiate alkaloid. These heterogenous behavioral responses, which were all antagonized by naloxone, indicate that multiple types of receptors mediate the effects of opiates in the central nervous system.     

Autoradiographic localization of opioid binding sites combined with immunogold detection of Leu-enkephalin,crustacean hyperglycaemic hormone and moult inhibiting hormone at the electron microscopic level in the sinus gland of the shore crab,Carcinus maenas

Double labelling experiments were performed on the same tissue section at the electron microscopic level, in order to show the involvement of the opioid leucine-enkephalin (Leu-enk) in the modulation of crustacean hyperglycaemic hormone (CHH) mobilization. Both neuropeptides were stored in distinct axon terminals of the sinus gland ofCarcinus maenas. A post-embedding immunogold cytochemical technique for Leuenk, CHH and the CHH neurohormone related moult inhibiting hormone (MIH) was combined with a scintillator intensified autoradiographic method to demonstrate binding of the opioid antagonist [³H] naloxone. Ultrathin sections were successively incubated with antisera against Leu-enk, CHH or MIH, and the corresponding colloidal gold labelled antisera, followed by autoradiographic processing. At the ultrastructural level [³H] naloxone binding sites were easily recognized by their silver tracks after development. Opioid binding sites for [³H] naloxone were visualized only at membranes of CHH-containing axon terminals. These results provide morphological evidence for direct enkephalinergic control of CHH containing neurons in the sinus gland ofC. maenas and are furthermore the first autoradiographic demonstration of opioid binding sites in the nervous system of invertebrates.     

Codeine and 6-Acetylcodeine Analgesia in Mice

Summary 1. Acetylation of morphine at the 6-position changes its pharmacology. To see if similar changes are seen with codeine, we examined the analgesic actions of codeine and 6-acetylcodeine.2. Like codeine, 6-acetylcodeine is an effective analgesic systemically, supraspinally and spinally, with a potency approximately a third that of codeine.3. The sensitivity of 6-acetylcodeine analgesia to the mu-selective antagonists β-FNA and naloxonazine confirmed its classification as a mu opioid. However, it differed from the other mu analgesics in other paradigms.4. Antisense mapping revealed the sensitivity of 6-acetylcodeine to probes targeting exons 1 and 2 of the mu opioid receptor gene (Oprm), a profile distinct from either codeine or morphine. Although heroin analgesia also is sensitive to antisense targeting exons 1 and 2, heroin analgesia also is sensitive to the antagonist 3-O-methylnaltrexone, while 6-acetylcodeine analgesia is not.5. Thus, 6-acetylcodeine is an effective mu opioid analgesic with a distinct pharmacological profile.