401. The noradrenaline precursor L-threo-3,4-dihydroxyphenylserine exhibits antinociceptive activity via central alpha-adrenoceptors in the mouse.
- Author
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Kawabata A, Kasamatsu K, Umeda N, and Takagi H
- Subjects
- Administration, Oral, Adrenergic alpha-1 Receptor Antagonists, Adrenergic alpha-2 Receptor Antagonists, Adrenergic alpha-Antagonists administration & dosage, Adrenergic alpha-Antagonists pharmacology, Analgesics administration & dosage, Analgesics antagonists & inhibitors, Animals, Benserazide pharmacology, Droxidopa administration & dosage, Droxidopa antagonists & inhibitors, Injections, Intraventricular, Injections, Spinal, Injections, Subcutaneous, Male, Mice, Mice, Inbred Strains, Naloxone pharmacology, Pain Measurement drug effects, Receptors, Adrenergic, alpha-1 drug effects, Receptors, Adrenergic, alpha-2 drug effects, Spinal Cord drug effects, Analgesics pharmacology, Droxidopa pharmacology, Receptors, Adrenergic, alpha drug effects
- Abstract
1. Systemic (s.c. or p.o.) administration of L-threo-3,4-dihydroxyphenylserine (droxidopa, L-threo-DOPS; L-DOPS), a noradrenaline precursor, at a dose-range of 100-800 mg kg-1, produced naloxone-resistant antinociception in a dose-dependent manner in the mouse, as assessed by the tail flick test, kaolin-induced writhing test and formalin-induced nociception test. 2. Antinociception elicited by L-DOPS (400 mg kg-1, s.c.) was not affected by s.c. injection of benserazide, a peripherally preferential L-aromatic amino acid decarboxylase inhibitor, but was suppressed by its intracerebroventricular (i.c.v.) injection. 3. I.c.v. or intrathecal (i.t.) administration of the non-selective alpha-blocker, phentolamine, significantly reduced L-DOPS-induced antinociception. 4. I.c.v. administration of the alpha 1-blocker, prazosin, but not the alpha 2-blocker, yohimbine, abolished the antinociceptive effects of L-DOPS. In contrast, both blockers, when administered i.t., exhibited significant inhibitory effects. 5. These results suggest that systemic L-DOPS produces opioid-independent antinociception, mediated by supraspinal alpha 1-adrenoceptors and by spinal alpha 1- and alpha 2-adrenoceptors and may predict additional therapeutic applications of L-DOPS as an analgesic.
- Published
- 1994
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