| 1. |
- Abelson, Klas, 1976-
(author)
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Acetylcholine in Spinal Pain Modulation : An in vivo Study in the Rat
- 2005
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Doctoral thesis (other academic/artistic)abstract
- The spinal cord is an important component in the processing and modulation of painful stimuli. Nerve signals from the periphery are relayed and further conducted to the brain (nociception) in the spinal cord, and the most essential modulation of painful information (antinociception) occurs here. Several neurotransmitters are involved in spinal pain modulation, among them acetylcholine. However, the role of acetylcholine has previously been little investigated. In the present thesis, the acetylcholine release in the spinal cord was studied in vivo. By using spinal microdialysis on anaesthetised rats, the effects on the intraspinal acetylcholine release of various receptor ligands and analgesic agents were examined. This, together with pain behavioural tests and in vitro pharmacological assays, was used to evaluate the role of acetylcholine in spinal pain modulation. The four studies in this thesis resulted in the following conclusions: An increased release of spinal acetylcholine is associated with an elevated pain threshold, while a decreased acetylcholine release is associated with hyperalgesia, as seen after systemic treatment with a muscarinic agonist and an antagonist. Lidocaine is a potent analgesic when given systemically. It was found to produce an increase of intraspinal acetylcholine after intravenous injection of analgesic doses. This effect was attenuated after muscarinic, and abolished after nicotinic, receptor blockade. Various a2-adrenergic ligands, associated with nociceptive or antinociceptive effects, were found to affect intraspinal acetylcholine release via action on nicotinic receptors. Finally, the involvement of spinal acetylcholine in the analgesic effects of aspirin and paracetamol was examined. It was found that spinal acetylcholine could participate in the analgesic effects of aspirin, but not of paracetamol. The present thesis provides data that clearly demonstrate a relationship between intraspinal acetylcholine and antinociception, and elucidate interactions between acetylcholine and other mechanisms that mediate antinociception in the spinal cord.
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| 2. |
- Abelson, Klas, et al.
(author)
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High plasma corticosterone levels persist during frequent automatic blood sampling in rats
- 2005
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In: In Vivo. - 0258-851X .- 1791-7549. ; 19:5, s. 815-19
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Journal article (peer-reviewed)abstract
- Corticosterone levels in blood may be used as a marker of stress in rodents, provided that the blood sampling procedure itself is non-stressful. Automated blood sampling equipment (Accusampler®) allows blood sampling without any interference with the animal and might be useful as a tool for an on-line measurement of stress markers in blood. However, the impact of the blood sampling itself on the corticosterone levels in blood is unknown. The present study was designed to evaluate whether the frequency of blood sampling influences the plasma corticosterone levels in male and female rats. During anaesthesia, a catheter was placed in the jugular vein and attached to an Accusampler®. Blood samples (200 μl) were withdrawn with a high (24 samples) or low frequency (3 samples) during a six-hour period immediately after the catheter insertion. The corticosterone levels in the plasma were quantified with ELISA. The corticosterone levels persisted at high post-operation concentrations when blood was collected frequently, while the levels steadily declined significantly during low-frequency sampling. The corticosterone levels were higher in female than in male rats, but the curves were similar. The present study elucidates the importance of considering the frequency of blood withdrawal during automated blood sampling. This parameter may have an impact on the experimental results when using blood corticosterone levels as a stress marker, but also during any in vivo study where blood is collected, since high corticosterone levels may affect the normal physiology of the animals.
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| 3. |
- Abelson, Klas, et al.
(author)
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Intravenously administered lidocaine in therapeutic doses increases the intraspinal release of acetylcholine in rats
- 2002
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In: Neuroscience Letters. - : Elsevier. - 0304-3940 .- 1872-7972. ; 317:2, s. 93-6
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Journal article (peer-reviewed)abstract
- The local anesthetic lidocaine suppresses different pain conditions when administered systemically. Part of the antinociceptive effect appears to be mediated via receptor mechanisms. We have previously shown that muscarinic and nicotinic agonists that produce antinociception increase the intraspinal release of acetylcholine. In the present study it was hypothesized that systemically administered lidocaine is acting through the same mechanisms as cholinergic agonists and affects the intraspinal release of acetylcholine. Microdialysis probes were placed in anesthetized rats for sampling of acetylcholine. Ten and 30 mg/kg lidocaine injected intravenously significantly increased the intraspinal release of acetylcholine. The effect of lidocaine could be reduced by pretreatment with intraspinally administered atropine or mecamylamine. Our results suggest that the antinociceptive effect produced by systemically administered lidocaine is mediated through an action on muscarinic and nicotinic receptors.
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| 4. |
- Abelson, Klas, et al.
(author)
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Intravenously administered oxotremorine and atropine, in doses known to affect pain threshold, affect the intraspinal release of acetylcholine in rats
- 2002
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In: Pharmacology and Toxicology. - : Blackwell. - 0901-9928 .- 1600-0773. ; 90:4, s. 187-192
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Journal article (peer-reviewed)abstract
- Abstract:Both systemically and intrathecally administered cholinergic agonists produce antinociception while cholinergic antagonists decrease pain threshold. The mechanism and the site of action of these substances are not known. In the present study it was hypothesized that systemically administered muscarinic agonists and antagonists modify nociceptive threshold by affecting intraspinal release of acetylcholine (ACh). Catheters were inserted into the femoral vein in rats maintained on isoflurane anaesthesia for administration of oxotremorine (10–300 μg/kg) and atropine (0.1, 10, 5000 μg/kg). Spinal microdialysis probes were placed intraspinally at approximately the C2–C5 spinal level for sampling of acetylcholine and dialysis delivery of atropine (0.1, 1, 10 nM). Additionally, the tail-flick behaviour was tested on conscious rats injected intraperitoneally with saline, atropine (10, 100 and 5000 μg/kg), or subcutaneously with oxotremorine (30, 100, 300 μg/kg). Subcutaneous administration of oxotremorine (30, 100, 300 μg/kg) significantly increased the tail-flick latency. These doses of oxotremorine dose-dependently increased the intraspinal release of acetylcholine. Intravenously administered atropine, in a dose that produced hyperalgesia (5000 μg/kg) in the tail-flick test, significantly decreased the intraspinal release of acetylcholine. Our results suggest an association between pain threshold and acetylcholine release in spinal cord. It is also suggested that an approximately 30% increase in basal ACh release produces antinociception and that a 30% decrease in basal release produces hyperalgesia.
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| 5. |
- Abelson, Klas S. P., et al.
(author)
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Distribution of [3H]-corticosterone in urine, feces and blood of male Sprague-Dawley rats after tail vein and jugular vein injections
- 2009
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In: In Vivo. - : International Institute of Anticancer Research. - 0258-851X .- 1791-7549. ; 23:3, s. 381-386
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Journal article (peer-reviewed)abstract
- The present study aimed to investigate the time-course and distribution of [(3)H]-corticosterone in urine, feces and blood of male Sprague-Dawley rats after intravenous administration of a low dose (1 microCi), and to investigate whether different intravenous routes of administration may affect the dynamics of excreted [(3)H]-corticosterone in the feces. One microCi [(3)H]-corticosterone was injected intravenously either through the tail vein in manually restrained rats or through a jugular vein catheter three days after surgical implantation. Urine and feces were collected at different time points over 78 h from the rats injected in the tail vein, and blood and feces were collected over 48 h from rats injected in the jugular vein. In the blood, radioactivity peaked immediately and decreased rapidly within 90 minutes. The radioactivity was excreted in urine within six h and in feces after at least 12 h. Sixty percent of the radioactivity was detected in the urine and 40% in feces during the study period of 78 h. The detected amount of radioactivity in feces was higher and displayed a more pronounced peak 12 h after injection when the substance was administered through a jugular vein catheter compared to tail vein injection. The data obtained in the present study may serve as an important benchmark when choosing time points for fecal collection for quantification of corticosterone or corticosterone metabolites as a non-invasive measure of preceding HPA-axis activation.
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| 6. |
- Abelson, Klas S. P., et al.
(author)
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Voluntary ingestion of nut paste for administration of buprenorphine in rats and mice
- 2012
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In: Laboratory Animals. - : SAGE Publications. - 0023-6772 .- 1758-1117. ; 46:4, s. 349-351
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Journal article (peer-reviewed)abstract
- An adequate analgesic strategy is important to improve the postoperative recovery and welfare of laboratory rats and mice. It is desirable that the method for administering the drug is non-invasive and stress-free. We have previously validated a method for administering buprenorphine in a nut paste for voluntary ingestion. This method has many advantages over parenteral administration. To use the method in a successful way, however, it is important to prepare and administer the mix correctly. The present paper describes in detail how to implement the method, by means of habituation, presentation, adequate concentrations and amounts of buprenorphine/nut paste, and dosage of buprenorphine to rats and mice.
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| 7. |
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| 9. |
- Abelson, Klas, et al.
(author)
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The effects of the alpha2-adrenergic receptor agonists clonidine and rilmenidine, and antagonists yohimbine and efaroxan, on the spinal cholinergic receptor system in the rat
- 2004
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In: Basic & Clinical Pharmacology & Toxicology. - : Blackwell. - 1742-7835 .- 1742-7843. ; 94:4, s. 153-60
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Journal article (peer-reviewed)abstract
- Cholinergic agonists produce spinal antinociception via mechanisms involving an increased release of intraspinalacetylcholine. The cholinergic receptor system interacts with several other receptor types, such as a2-adrenergic receptors.To fully understand these interactions, the effects of various receptor ligands on the cholinergic system must be investigatedin detail. This study was initiated to investigate the effects of the a2-adrenergic receptor agonists clonidine and rilmenidineand the a2-adrenergic receptor antagonists yohimbine and efaroxan on spinal cholinergic receptors in the rat. Spinalmicrodialysis was used to measure in vivo changes of acetylcholine after administration of the ligands, with or withoutnicotinic receptor blockade. In addition, in vitro binding properties of the ligands on muscarinic and nicotinic receptorswere investigated. It was found that clonidine and rilmenidine increased, while yohimbine decreased spinal acetylcholinerelease. Efaroxan affected acetylcholine release differently depending on concentration. Nicotinic receptor blockade atten-uated the effect of all ligands. All ligands showed poor binding affinity for muscarinic receptors. On the other hand, allligands possessed affinity for nicotinic receptors. Clonidine and yohimbine binding was best fit to a one site binding curveand rilmenidine and efaroxan to a two site binding curve. The present study demonstrates that the tested a2-adrenergicreceptor ligands affect intraspinal acetylcholine release in the rat evoked by nicotinic receptor mechanisms in vivo, andthat they possess binding affinity to nicotinic receptors in vitro. The binding of a2-adrenergic receptor ligands to nicotinicreceptors might affect the intraspinal release of acetylcholine.
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