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. Author manuscript; available in PMC: 2014 May 21.
Published in final edited form as: Pain. 2006 Nov 22;129(0):35–45. doi: 10.1016/j.pain.2006.09.033

Figure 2.

Figure 2

Antinociceptive tolerance to spinal morphine induced by sustained morphine exposure is prevented by SP-SAP. Male Sprague Dawley rats received i.th. injections of SP-SAP, SAP or saline and 28 days later either morphine (open symbols) or saline minipumps (closed symbols). Antinociceptive dose-response functions for i.th. morphine were generated before minipump implantation (Baseline) and 6 days after minipump implantation in the 52°C hot water tail-flick test. Each group of rats was tested with only one dose, 30 min after i.th. morphine injection. The dose-effect curve for i.th. morphine in groups with morphine minipumps and previous i.th. injections of SAP or saline was shifted significantly to the right of that for animals with saline minipumps (P<0.05). This dose-effect curve of animals with morphine minipumps and previous i.th. injection of SP SAP was not different from that of the animals with saline minipumps or baseline. There were 6 animals per dose.