okadaic-acid and Pain

Buprenorphine displays attributes of opioids, but also some features distinct from them. We examined spinal and supraspinal signal transduction of buprenorphine-induced anti-nociception in mice compared with morphine and fentanyl.. The opioid receptor antagonist naloxone, Pertussis toxin (PTX), G(z) protein antisense and nociceptin/orphanin-FQ receptor agonist nociceptin, and antagonist, JTC-801, were injected supraspinally (intracerebroventricular) and spinally (intrathecal). Also the cell-permeable Ser/Thr protein phosphatase inhibitor okadaic acid was given supraspinally.. Spinal naloxone (20 microg) or PTX (1 microg) attenuated morphine, fentanyl and buprenorphine (s.c.) anti-nociception. Supraspinal naloxone or PTX attenuated morphine and fentanyl, but not buprenorphine anti-nociception. Spinal G(z) protein antisense did not alter buprenorphine, morphine or fentanyl anti-nociception and supraspinal G(z)-antisense did not alter morphine or fentanyl anti-nociception. However, supraspinal G(z)-antisense (not random sense) reduced buprenorphine anti-nociception. Peripheral JTC-801 (1 mgxkg(-1), i.p.) enhanced the ascending (3 mgxkg(-1)) and descending (30 mgxkg(-1)) portions of buprenorphine's dose-response curve, but only spinal, not supraspinal, nociceptin (10 nmolxL(-1)) enhanced buprenorphine anti-nociception. Intracereboventricular okadaic acid (0.001-10 pg) produced a biphasic low-dose attenuation, high-dose enhancement of buprenorphine(3 or 30 mgxkg(-1), s.c.) anti-nociception, but did not affect morphine or fentanyl anti-nociception.. Buprenorphine has an opioid component to its supraspinal mechanism of analgesic action. Our present results reveal an additional supraspinal component insensitive to naloxone, PTX and nociceptin/orphanin-FQ, but involving G(z) protein and Ser/Thr protein phosphatase. These data might help explain the unique preclinical and clinical profiles of buprenorphine.

Topics: Acetylcholine; Adrenergic alpha-Antagonists; Aminoquinolines; Analgesics, Opioid; Anesthetics, Local; Animals; Benzamides; Brain; Buprenorphine; Disease Models, Animal; Dose-Response Relationship, Drug; Enzyme Inhibitors; Fentanyl; GTP-Binding Proteins; Injections, Intraventricular; Injections, Spinal; Male; Mice; Morphine; Naloxone; Narcotic Antagonists; Nociceptin; Nociceptin Receptor; Okadaic Acid; Oligonucleotides, Antisense; Opioid Peptides; Pain; Pain Measurement; Pain Threshold; Pertussis Toxin; Phosphoprotein Phosphatases; Piperazines; Pyridines; Receptor, Serotonin, 5-HT1A; Receptors, Opioid; Serotonin 5-HT1 Receptor Antagonists; Serotonin Antagonists; Signal Transduction; Yohimbine

Glutamatergic inputs arising from the parabrachial nucleus to neurons in the lateral sector of the central amygdala were studied in vitro. Tetanic stimulation of these inputs led to LTP that did not require activation of NMDA receptors or a rise of postsynaptic calcium. LTP was accompanied by a reduction in the paired-pulse ratio, indicating that LTP results from an increase in transmitter release probability. Activation of adenylyl cyclase with forskolin potentiated these inputs with a similar reduction in paired-pulse facilitation and occluded LTP induction. LTP was inhibited by the protein kinase A blocker H89. Low-frequency stimulation led to LTD that required activation of postsynaptic NMDA receptors and a rise in postsynaptic calcium. There was no change in paired-pulse facilitation with LTD. LTD was blocked by protein phosphatase blockers calyculin and okadaic acid. We conclude that parabrachial inputs to the lateral sector of the central amygdala show presynaptic LTP that requires activation of a presynaptic protein kinase A via a calcium-dependent adenylyl cyclase while LTD at the same synapses is postsynaptic and requires a rise in postsynaptic calcium and activation of protein phosphatase.

Topics: Adenylyl Cyclases; Amygdala; Animals; Calcium Signaling; Colforsin; Cyclic AMP-Dependent Protein Kinases; Electric Stimulation; Enzyme Activation; Enzyme Activators; Enzyme Inhibitors; Excitatory Postsynaptic Potentials; Glutamic Acid; In Vitro Techniques; Isoquinolines; Long-Term Potentiation; Long-Term Synaptic Depression; Neuronal Plasticity; Neurons, Afferent; Nociceptors; Okadaic Acid; Pain; Phosphoprotein Phosphatases; Presynaptic Terminals; Rats; Rats, Wistar; Receptors, N-Methyl-D-Aspartate; Sulfonamides; Synaptic Transmission

The possible participation of the nitric oxide (NO)-cyclic GMP-protein kinase G (PKG) pathway on gabapentin-induced spinal antiallodynic activity was assessed in spinal nerve injured rats. Intrathecal gabapentin, diazoxide or pinacidil reduced tactile allodynia in a dose-dependent manner. Pretreatment with NG-L-nitro-arginine methyl ester (L-NAME, non-specific inhibitor of NO synthase NOS), 7-nitroindazole (neuronal NO synthase inhibitor), 1H-[1,2,4] -oxadiazolo [4,3-a] quinoxalin-1-one (ODQ, guanylyl cyclase inhibitor) or (9S, 10R, 12R)-2,3,9,10,11,12-hexahydro-10-methoxy-2,9-dimethyl-1-oxo-9,12-epoxy-1H-diindolo-[1,2,3-fg:3',2',1'-kl]pyrrolo[3,4-i][1,6]benzodiazocine-10-carboxylic acid methyl ester (KT-5823, specific PKG inhibitor), but not NG-D-nitro-arginine methyl ester (D-NAME) or okadaic acid (protein phosphatase 1 and 2 inhibitor) prevented gabapentin-induced antiallodynia. Pinacidil activity was not blocked by L-NAME, D-NAME, 7-nitroindazole, ODQ, KT-5823 or okadaic acid. Moreover, KT-5823, glibenclamide (ATP-sensitive K+ channel blocker), apamin and charybdotoxin (small- and large-conductance Ca2+-activated K+ channel blockers, respectively), but not margatoxin (voltage-gated K+ channel blocker), L-NAME, 7-nitroindazole, ODQ or okadaic acid, reduced diazoxide-induced antiallodynia. Data suggest that gabapentin-induced spinal antiallodynia could be due to activation of the NO-cyclic GMP-PKG-K+ channel pathway.

Topics: Amines; Analgesics; Animals; Apamin; Carbazoles; Charybdotoxin; Cyclic GMP; Cyclic GMP-Dependent Protein Kinases; Cyclohexanecarboxylic Acids; Diazoxide; Dose-Response Relationship, Drug; Enzyme Inhibitors; Female; Gabapentin; gamma-Aminobutyric Acid; Glyburide; Indazoles; Indoles; Injections, Spinal; NG-Nitroarginine Methyl Ester; Nitric Oxide; Nitric Oxide Synthase; Okadaic Acid; Oxadiazoles; Pain; Pinacidil; Potassium Channel Blockers; Potassium Channels; Protein Kinase Inhibitors; Quinoxalines; Rats; Rats, Wistar; Signal Transduction; Spinal Nerves; Stereoisomerism; Time Factors; Vasodilator Agents

Protein kinases and phosphatases catalyze opposing reactions of phosphorylation and dephosphorylation, which may modulate the function of crucial signaling proteins in central nervous system. This is an important mechanism in the regulation of intracellular signal transduction pathways in nociceptive neurons. To explore the role of protein phosphatase in central sensitization of spinal nociceptive neurons following peripheral noxious stimulation, using electrophysiological recording techniques, we investigated the role of two inhibitors of protein phosphatase type 2A (PP2A), fostriecin and okadaic acid (OA), on the responses of dorsal horn neurons to mechanical stimuli in anesthetized rats following intradermal injection of capsaicin. Central sensitization was initiated by injection of capsaicin into the plantar surface of the left paw. A microdialysis fiber was implanted in the spinal cord dorsal horn for perfusion of ACSF and inhibitors of PP2A, fostriecin and okadaic acid. We found that in ACSF pretreated animals, the responses to innocuous and noxious stimuli following capsaicin injection increased over a period of 15 min after injection and had mostly recovered by 60 min later. However, pre- or post-treatment with the phosphatase inhibitors, fostriecin or OA, significantly enhanced the effects of capsaicin injection by prolonging the responses to more than 3 hours. These results confirm that blockade of protein phosphatase activity may potentiate central sensitization of nociceptive transmission in the spinal cord following capsaicin injection and indicate that protein phosphatase type 2A may be involved in determining the duration of capsaicin-induced central sensitization.

Topics: Afferent Pathways; Alkenes; Animals; Capsaicin; Disease Models, Animal; Enzyme Inhibitors; Inflammation Mediators; Male; Nociceptors; Okadaic Acid; Pain; Pain Threshold; Phosphoprotein Phosphatases; Physical Stimulation; Polyenes; Posterior Horn Cells; Pyrones; Rats; Rats, Sprague-Dawley; Reaction Time; Synaptic Transmission; Time Factors

Although the serine/threonine protein kinases involved in the pharmacological action of morphine are well recognized, the critical contribution of serine/threonine protein phosphatase (PP) has been appreciated on to a slight degree. We examined the involvement of subtypes of serine/threonine protein phosphatase (PP) in the antinociceptive effect of morphine in mice. The antinociceptive effect of subcutaneously administered morphine was attenuated by simultaneously intracerebroventricular (i.c.v.) or intrathecal (i.t.) injection of okadaic acid (OA), a PP inhibitor. To reveal which subtypes of PPs participated in the antinociceptive effect of morphine, mice received i.c.v. or i.t. injections of antisense oligodeoxynucleotide (AS-ODN) directed against either the PP 2 A or PP5 subtypes of PPs before assessment of morphine-induced antinociception. Pretreatment with AS-ODN against PP 2 A or PP5 via each route weakened the antinociceptive effect of morphine, accompanied by reduction of expression levels of PP in the periaqueductal gray (PAG) and the spinal cord. Subcutaneously administered morphine increased activity of OA-sensitive PPs in the PAG and the spinal cord in a dose-dependent manner; this was prevented by concurrent administration of naloxone. These results suggest that PP 2 A and PP5 are involved in the antinociceptive effect of morphine in mice.

Topics: Animals; Area Under Curve; Blotting, Western; Brain; Dose-Response Relationship, Drug; Drug Administration Routes; Drug Interactions; Enzyme Activation; Enzyme Inhibitors; Male; Mice; Mice, Inbred ICR; Morphine; Naloxone; Narcotics; Nuclear Proteins; Okadaic Acid; Pain; Phosphoprotein Phosphatases; Phosphorylation; Serine; Threonine; Time Factors

The aim of this study was to evaluate the effects of serine/threonine protein phosphatase (PP) inhibitors on morphine-induced antinociception in the tail flick test in mice, and on [3H]naloxone binding to the forebrain crude synaptosome fraction. Neither okadaic acid nor cantharidin (1-10000 nM) displaced [3H]naloxone from its specific binding sites, which indicates that they do not interact at the opioid receptor level. The i.c.v. administration of very low doses of okadaic acid (0.001-1 pg/mouse) and cantharidin (0.001-1 ng/mouse), which inhibit PP2A, produced a dose-dependent antagonism of the antinociception induced by morphine (s.c.). However, L-nor-okadaone (0.001 pg/mouse-1 ng/mouse, i.c.v.), an analogue of okadaic acid lacking activity against protein phosphatases, did not affect the antinociceptive effect of morphine. On the other hand, high doses of okadaic acid (10 ng/mouse, i.c.v.) and cantharidin (1 microg/mouse, i.c.v.), which also block PP1, and calyculin-A (0.1 fg/mouse-1 ng/mouse, i.c.v.), which inhibits equally both PP1 and PP2A, did not modify the morphine-induced antinociception. These results suggest that the activation of type 2A serine/threonine protein phosphatases may play a role in the antinociceptive effect of morphine, and that PP1 might counterbalace this activity.

Topics: Analgesics, Opioid; Animals; Binding, Competitive; Cantharidin; Dose-Response Relationship, Drug; Enzyme Inhibitors; Female; Injections, Intraventricular; Marine Toxins; Mice; Morphine; Naloxone; Nociceptors; Okadaic Acid; Oxazoles; Pain; Pain Measurement; Phosphoprotein Phosphatases; Prosencephalon; Synaptosomes; Tritium

In this study we have evaluated the mechanisms mediating the prolonged hyperalgesia induced by administration of prostaglandin E2 plus rolipram, an inhibitor of type IV phosphodiesterase. The Randall-Selitto paw pressure device was employed to measure the effect of intradermal injection of test agents on the time course of the decrease in mechanical nociceptive threshold produced by prostaglandin E2 plus rolipram in the hairy skin of the hindpaw of the rat. The intradermal injection of prostaglandin E2 produced a dose-dependent decrease in the nociceptive threshold which lasted approximately 2 h. While rolipram alone had no significant effect on nociceptive threshold, it enhanced and prolonged (> 72 h) prostaglandin E2-induced hyperalgesia. WIPTIDE, a protein kinase A inhibitor, when administered 30 min after prostaglandin E2, or with prostaglandin E2 plus rolipram, a time when prostaglandin E2-induced hyperalgesia was at its peak, produced a significant reduction in hyperalgesia. However, at 90 or at 180 min after injection of prostaglandin E2 plus rolipram, WIPTIDE was found to be without effect. H-8, a protein kinase G inhibitor, and okadaic acid, a protein phosphatase inhibitor, when administered 30 min after prostaglandin E2, or 180 min after prostaglandin E2 plus rolipram, produced no significant effect. However, when administered 90 min after prostaglandin E2 plus rolipram, each produced a significant reduction in the hyperalgesia induced by prostaglandin E2 plus rolipram.(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: 8-Bromo Cyclic Adenosine Monophosphate; Aminoquinolines; Animals; Calcium; Carrier Proteins; Cyclic AMP; Dinoprostone; Ethers, Cyclic; Gallic Acid; Hyperalgesia; Intracellular Signaling Peptides and Proteins; Isoquinolines; Male; Okadaic Acid; Pain; Phosphodiesterase Inhibitors; Pyrrolidinones; Rats; Rats, Sprague-Dawley; Rolipram; Second Messenger Systems; Sympathectomy; Sympathetic Fibers, Postganglionic; Time Factors