Figure 2

Intensity of astrocyte labelling in the dorsal lumbar spinal cord of rats. (A) Representative photomicrographs acquired by confocal microscopy of spinal cord sections labelled for the astrocytic protein, glial fibrillary acidic protein (GFAP). Spinal cord sections were collected from rats receiving intrathecal vehicle (saline; SAL) (i), morphine (15 μg; MS) (ii), morphine and naltrexone (5 ng; MS+NTX) (iii), or naltrexone (NTX) alone (iv). Photomicrographs were converted to gray scale and then analyzed to obtain mean gray values. Morphine treatment produced a significant increase in the amount of GFAP labelling as compared with saline-treated control. Attenuation of increased GFAP immuno-labelling was observed in animals co-administered ultra-low dose naltrexone with morphine (^### = p < 0.001 compared to morphine treatment). Naltrexone alone had no significant effect on GFAP immuno-labelling compared to saline control (p > 0.05). Data represent means ± s.e.m. for n = 6-8 sections per rat from n = 5-6 per group. Statistical analyses were performed by a one-way ANOVA followed by Tukey's post-hoc multiple comparison test. The asterisk denotes significant difference from saline-treated rats, *** = p < 0.001.