| 1. |
- Abelson, Klas, et al.
(författare)
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Intravenously administered lidocaine in therapeutic doses increases the intraspinal release of acetylcholine in rats
- 2002
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Ingår i: Neuroscience Letters. - : Elsevier. - 0304-3940 .- 1872-7972. ; 317:2, s. 93-6
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Tidskriftsartikel (refereegranskat)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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| 2. |
- Abelson, Klas, et al.
(författare)
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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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Ingår i: Pharmacology and Toxicology. - : Blackwell. - 0901-9928 .- 1600-0773. ; 90:4, s. 187-192
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Tidskriftsartikel (refereegranskat)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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| 4. |
- Abelson, Klas, et al.
(författare)
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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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Ingår i: Basic & Clinical Pharmacology & Toxicology. - : Blackwell. - 1742-7835 .- 1742-7843. ; 94:4, s. 153-60
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Tidskriftsartikel (refereegranskat)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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