Hung KC, Wu HE, Mizoguchi H, Leitermann R, Tseng LF. Intrathecal Treatment With 6-Hydroxydopamine or 5,7-Dihydroxytryptamine Blocks the Antinociception Induced by Endomorphin-1 and Endomorphin-2 Given Intracerebroventricularly in the Mouse.
J Pharmacol Sci 2003;
93:299-306. [PMID:
14646247 DOI:
10.1254/jphs.93.299]
[Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022] Open
Abstract
The involvement of spinopetal noradrenergic and serotonergic systems in antinociception induced by endomorphin-1 (EM-1) and endomorphin-2 (EM-2) given supraspinally or spinally were investigated in male CD-1 mice. Groups of mice were pretreated intrathecally (i.t.) with 6-hydroxydopamine (6-OHDA, 20 microg) or 5,7-dihydroxytryptamine (5,7-DHT, 50 microg) for 3 days before intracerebroventricular (i.c.v.) or i.t. injection of different doses of EM-1 or EM-2, and the tail-flick response was measured for antinociceptive effects. I.t. pretreatment with 6-OHDA for 3 days, which markedly depleted noradrenaline (NA) contents by more than 90%, but not serotonin (5-HT) in the spinal cord, completely abolished the antinociception induced by i.c.v.-administered EM-1 or EM-2. Intrathecal pretreatment with 5,7-DHT for 3 days, which markedly reduced 5-HT contents by more than 92%, but only reduced NA by 14 - 25% in the spinal cord, also markedly attenuated the antinociception induced by i.c.v.-administered EM-1 or EM-2. However, the antinociception induced by i.t.-administered EM-1 or EM-2 was not affected in either 6-OHDA or 5,7-DHT pretreated mice. It is concluded that NA and 5-HT in the spinal cord are involved in the antinociception induced by supraspinally, but not spinally administered EM-1 and EM-2.
Collapse