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. Author manuscript; available in PMC: 2013 Jul 23.
Published in final edited form as: Eur J Pharmacol. 2007 Jun 5;571(1):1–7. doi: 10.1016/j.ejphar.2007.05.033

Fig 2.

Fig 2

Pretreatment with (−)-morphine given into ventral periaqueductal gray dose-dependently attenuates the tail-flick inhibition produced by (−)-morphine given into ventral periaqueductal gray in the rat. Groups of rats were microinjected with a various dose (0.3 to 3000 pmol) of (−)-morphine or vehicle given into the ventral periaqueductal gray 45 min before the microinjection of (−)-morphine (9 nmol) given into the ventral periaqueductal gray and the tail-flick response was measured 20 min after (−)-morphine challenge. Each column represents the mean and vertical bar represents the S.E.M. with 5-8 rats in each group. One-way ANOVA followed by Dunnett's post-test was used to test the difference between groups; the F (7,41) = 16.93; * p < 0.05, ** p < 0.01, compared with the vehicle pretreated rats challenged with (−)-morphine (the second column from the left).