Table 1.

Antiallodynic Effect of Intrathecally Administered R-PIA against Cold Allodynia

Time (min)	0	15	30	45	60	90	120	180
Normal	0.5 ± 0.1	0.7 ± 0.1	0.6 ± 0.1	0.6 ± 0.1	0.5 ± 0.1	0.7 ± 0.1	0.6 ± 0.1	0.5 ± 0.1
V + S + S	13.2 ± 0.4*	13.4 ± 0.4*	12.9 ± 0.4*	12.9 ± 0.3*	13.4 ± 0.4*	12.9 ± 0.4*	13.2 ± 0.4*	13.0 ± 0.4*
V + S + R-PIA 0.3	12.6 ± 0.3*	11.7 ± 0.6*	11.5 ± 0.4*	11.8 ± 0.5*	12.5 ± 0.3*	11.6 ± 0.4*	12.2 ± 0.4*	12.7 ± 0.3*
V + DPCPX + R-PIA 0.3	12.7 ± 0.4*	12.6 ± 0.6*	12.3 ± 0.5*	12.1 ± 0.5*	11.8 ± 0.4*	12.4 ± 0.4*	12.2 ± 0.4*	12.7 ± 0.3*
V + S + R-PIA 1.0	13.2 ± 0.4*	4.2 ± 0.7*,†	4.9 ± 0.9*,†	6.8 ± 0.7*,†	6.6 ± 0.4*,†	7.7 ± 0.6*,†	10.0 ± 0.3*,†	11.0 ± 0.3*,†
V + DPCPX + R-PIA 1.0	13.1 ± 0.3*	11.4 ± 0.4*,‡	11.7 ± 0.4*,‡	12.2 ± 0.6*,‡	12.9 ± 0.2*,‡	12.4 ± 0.5*,‡	13.0 ± 0.2*,‡	13.3 ± 0.4*
V + S + R-PIA 3.0	13.4 ± 0.4*	0.7 ± 0.3†	1.3 ± 0.6†	2.0 ± 0.8†	3.2 ± 0.8*,†	3.7 ± 0.7*,†	5.6 ± 0.6*,†	6.7 ± 0.4*,†
V + DPCPX + R-PIA 3.0	13.0 ± 0.4*	11.1 ± 0.3*,§	10.6 ± 0.3*,§	11.2 ± 0.5*,§	11.2 ± 0.4*,§	11.7 ± 0.3*,§	12.7 ± 0.4*,§	12.9 ± 0.3*,§

Peripheral neuropathy was induced by the administration of vincristine (100 μg/kg, i.p.) for 10 days. On the 28th day, saline or DPCPX (10 μg/10 μl) was intrathecally administered 15 min before intrathecal R-PIA administration (1.0 μg/10 μl or 3.0 μg/10 μl). Cold allodynia was then assessed using the acetone drop test (seconds). Results are expressed as mean ± standard error of mean, n = 6 rats per group. One-way ANOVA followed by Tukey’s post hoc test.

^*P < 0.05 vs. normal control group,

^†P < 0.05 vs. vincristine control group,

^‡P < 0.05 vs. R-PIA 1.0 μg/10 μl group,

^§P < 0.05 vs. R-PIA 3.0 μg/10 μl group. V: vincristine, S: saline, DPCPX: 1,3-dipropyl-8-cyclopentylxanthine = adenosine A₁ receptor antagonist, R-PIA: N6-(2-phenylisopropyl)-adenosine R-(-)isomer = adenosine A₁ receptor agonist.