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KMID : 0390119930330010189
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Journal of Pusan Medical College
1993 Volume.33 No. 1 p.189 ~ p.202
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The Role of Locus Ceruleus in Forced Swimming-induced Analgesia as Revealed by Lesion Study in Rats
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Abstract
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The role of locus ceruleus(LC) in forced swimming-induced swimming-induced analgesia was studied by producing lesion at the region by microinjection of 6-yearoxydopamine in rats. Six days after the stereotaxic operation, pain sensitivities were
measured
before and after forced swimming, in parameters of tail flick latency(TFL) and forepaw lick latency(PLL). Clonidine (0.5mg/kg) or normal saline was injected intraperitoneally fifteen minutes before measurement of pain sensitivity.
@ES The results are summarized as follows:
@EN 1. Basal pain sensitivities with or without clonidine injection before forced swimming both tail flick latency and forepaw lick latency did not change after lesion of locus ceruleus.
2. Pain sensitivity as measured by PLL after forced swimming and clonidine administration was significantly more sensitive in the LC lesioned group than in the sham operation group. The same trend was also noted when pain sensitivity was
measured
by
TFL.
3. Forced swimming-induced analgesic effect was seen in both sham operation and locus ceruleus lesioned groups in the parameter of tail flick latency. This was noted in both clonidine and normal saline injected groups.
4. However, with the parameter of forepaw lick latency, the results were split; forced swimming-induced analgesic effect was proved in sham operation with clonidine and locus ceruleus lesion with normal saline and a trend to such an effect was
seen in
sham operation with normal saline, but not in locus ceruleus lesion with clonidine.
5. Pain sensitivity as measured by TFL and PLL after forced swimming was significantly reduced after clonidine administration than after normal saline adminstration in the sham operation group, but his difference was not observe in the LC
lesioned
group.
From these results, the author suggests that locus ceruleus serves a partial role in the mechanism of forced swimming-induced analgesia.
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