Enhanced alpha-2 adrenergic controls and spinal morphine... : NeuroReport (original) (raw)
Somatosensory Systems, Pain: PDF Only
Enhanced alpha-2 adrenergic controls and spinal morphine potency in inflammation
CACorresponding Author
Department of Pharmacology, University College London, Gower Street, London WC1 6BT, UK
Abstract
The antinociceptive potency of spinal morphine is enhanced in rats after carrageenan-induced inflammation. This electrophysiological study examines whether changes in alpha-2 adrenergic systems are responsible. Dorsal horn nociceptive neurones were recorded under halothane anaesthesia in normal animals and animals with carrageenan inflammation. There was a mild increase in potency of the selective alpha-2 adrenoceptor agonist dexmedetomidine following carrageenan (ED50 = 1 μ g). Intrathecal idazoxan (100 μ g), an alpha-2 antagonist, produced a significant facilitation of the C-fibre evoked response in carrageenan-treated but not normal animals. However since neither idazoxan (100 μ g) or atipamezole (50 μ g, another antagonist) influenced the potency of spinal morphine, the increased alpha-2 adrenergic activity in inflammation does not contribute to the enhanced potency of spinal morphine.
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