Rojas-Corrales MO, Berrocoso E, Micó JA. Role of 5-HT1A and 5-HT1B receptors in the antinociceptive effect of tramadol.
Eur J Pharmacol 2005;
511:21-6. [PMID:
15777775 DOI:
10.1016/j.ejphar.2005.02.006]
[Citation(s) in RCA: 32] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2004] [Revised: 01/27/2005] [Accepted: 02/01/2005] [Indexed: 11/25/2022]
Abstract
Tramadol, (1RS,2RS)-2-[(dimethylamine)-methyl]-1-(3-methoxyphenyl)-cyclohexanol hydrochloride, is an atypical centrally acting analgesic agent with relatively weak opioid receptor affinity and which, like some antidepressants, is able to inhibit the reuptake of serotonin (5-hydroxytryptamine, 5-HT) in the raphe nucleus. We have previously demonstrated that pindolol, a beta-adrenoceptor blocker/5-hydroxytryptamine(1A/1B) receptor antagonist, enhanced tramadol antinociception and that the selective 5-HT1A agonist 8-Hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT) reduced it. These effects were related to the negative feedback control that regulates raphe region neurones. The current study examines the ability of the selective antagonist at somatodendritic 5-HT1A receptors, N-[2-[4-(2-methoxyphenyl)-1-piperazinyl] ethyl]-N-(2-pyridinyl) cyclohexane carboxamide (WAY100635, 0.8 mg/kg), the selective antagonist at terminal 5-HT1B receptors, N-[3-(2-dimethylamino) ethoxy-4-methoxyphenyl]-2'-methyl-4'-(5-methyl-1,2,4-oxadiazol-3-yl)-(1,1'-biphenyl)-4-carboxamide (SB216641, 0.1-0.8 mg/kg) and the selective agonist at 5-HT1B receptors, 1,4-tDihydro-3-(1,2,3,6-tetrahydro-4-pyridinyl)-5H-pyrrolo[3,2-b] pyridin-5-one (CP93129, 0.2-0.4 mg/kg), to modify the antinociceptive effect of 4-64 mg/kg of tramadol in the hot plate test in mice. The results show that 0.8 mg/kg of WAY100635 enhanced antinociceptive effect of tramadol while neither agonism nor antagonism at the 5-HT1B receptor modifies it significantly at the doses tested. These results account for involvement of the somatodendritic 5-HT1A receptors in the analgesic effect of tramadol and support the supraspinal interaction of serotonin and the opioid system in the regulation of pain.
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