To investigate testosterone effect on nociception, tail flick latency(TFL, sec, 50±1℃) was measured before and after administration of antide (a gonadotropin releasing hormone antagonist) in male mice(Institute of Cancer Research, age of 7-8
weeks,
weight 30.5-37.5gm). Testosterone replacement effect on TFL was also exmined in antide pre-treated male mice.
Experiment 1:30 male mice were randomized into 3 groups(N=10 each). Antide 100㎍/kg, 300㎍/kg or same volume(5.7ml/kg) of 0.2% bovine serum albumin was administered intraperitoneally. TFL was measured before and at 3, 6, 9, 12 and 24 hours after
injection.
Experiment 2:40 novice male mice were randomized into 2 groups(N=20 each) and both groups were pre-treated with antide 300㎍/kg i.p. 6 hours after antide injection, testosterone 1mg/ke or same volume(5.7ml/kg) of sesame oil was adminstered i.p.
TFL
was
measured before and 6 hours after antide pre-treatment and 30 min after testosterone/vehicle injection.
1) TFL was significantly shortened by antide in dose dependent manner. In control group, baseline TFL(mean±SD) and those measured at 3, 6, 9, 12 and 24 hours after injection were 4.8±0.7, 5.6±0.7, 5.3±0.6, 5.4±0.6 and 4.7±0.6 sec,
respectively. In
antide 100㎍/kg group, TFLs were 5.2±0.9, 5.1±1.1, 4.2±0.9, 4.4±0.8, 5.1±0.8, and 4.7±0.8 sec, respectively. Compared with baseline, significant hyperalgesia appeared 6 and 9 hours after treatment. TFL measured at 6 hours after treatment
was
significantly shorter than control. In antide 300㎍/kg group, TFLs were 5.6±0.4, 4.5±0.9, 4.3±0.6, 3.9±1.0, 4.6±0.8 and 4.7±0.9 sec. Significant hyperalgesia appeared 3 hours after treatment and continued thereafter. TFLs measured at 3, 6
and
9
hours after treatment were significantly shorter than control, and TFL at 9 hours was significantly shorter than antide 100㎍/kg group.
2) Hyperalgesia induced by antide pre-treatment was recovered by testosterone replacement. In control group, TFL was shortened by antide pre-treatment(baseline : 6.1 ±0.8 sec; 6 hr after antide: 4.6±0.9 sec) disappeared after testosterone
replacement(6.0±0.8 sec).
From these results, it is suggested that testosterone has a role of maintaining baseline antinociception and acute decrease in testosterone level results in hyperalgesia.
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